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News Article | November 28, 2016
Site: www.eurekalert.org

With their potential for big savings through increased energy efficiency and reduced greenhouse gas emissions, interest in improving the manufacturing of superconductor wire is at an all-time high. The U.S. Department of Energy Monday announced a $4.5 million grant to Venkat Selvamanickam, MD Anderson Chair Professor of Mechanical Engineering at the University of Houston, to boost the advanced manufacturing of high-performance superconductor wires for next generation electric machines. The award is one of 13 projects funded to advance technologies for energy efficient electric motors through applied research and development. "Advancing these enabling technologies has the potential to boost the competitiveness of American manufacturers and take the development of more efficient electric machines a giant step further," Mark Johnson, director of DOE's Office of Energy Efficiency and Renewable Energy, said of the nearly $25 million in grant awards. "These technology R&D projects aim to significantly improve industrial motors for manufacturing, helping companies who use these motors in manufacturing save energy and money over the long run." Selvamanickam is one of the world's leading experts on manufacturing superconductors. He is the co-founder of SuperPower, which produces superconducting electrical wire, and has continued his research since joining the UH faculty in 2008. He also is director of the Advanced Research Hub at the Texas Center for Superconductivity at UH and manages the Advanced Manufacturing Institute at UH. "Superconducting motors and generators made with the wire that will be manufactured using the technology developed in this program can lead to more than six billion kilowatt hours of annual electricity savings and reduce CO2 emissions by nearly a million tons per year," he said. Superconductor devices are used in energy, health care and transportation, among other uses, and offer advantages including saving as much as 2 percent in electricity use in electric motors and generators and up to 10 percent in transmission and distribution equipment. That's because superconductors can transport electricity with little or no resistance, meaning energy isn't wasted in the electric machines and during transmission. "Dr. Selvamanickam is recognized globally for his focus on the development of innovative manufacturing technologies for thin film superconductor wire, which has been supported by the federal government, as well as the state of Texas and private industry," said Ramanan Krishnamoorti, interim vice president for research and technology transfer at UH. "This grant will allow him to continue his work to overcome obstacles to more efficiently manufacture the wire." The funding is part of the Obama Administration's Mission Innovation, an effort to double clean energy research and development investments over the next five years. The Energy Department last spring announced plans to fund up to $25 million in projects through the Next Generation of Electric Machines: Enabling Technologies funding opportunity, targeting technologies to boost efficiency in a cost-effective way. Selvamanickam said the funding will enable the use of superconducting machines at liquid nitrogen temperatures, which can lead to a widespread commercialization of this technology. Until now, superconducting machines, including motors and generators, have been built for use at lower temperatures because of performance limitations in the superconducting wire. The DOE-funded program will enable overcoming those limitations. His team was the first to manufacture thin film superconductor wire, which was used in 2008 to power 25,000 households in Albany, N.Y., and now is used by more than 200 institutions around the world for applications including wind generators, energy storage, power transmission cables, magnetically levitated trains, medical imaging and defense applications.


News Article | November 14, 2016
Site: www.eurekalert.org

With energy conservation expected to play a growing role in managing global demand, materials and methods that make better use of existing sources of energy have become increasingly important. Researchers reported this week in the Proceedings of the National Academy of Sciences that they have demonstrated a step forward in converting waste heat - from industrial smokestacks, power generating plants or even automobile tailpipes - into electricity. The work, using a thermoelectric compound composed of niobium, titanium, iron and antimony, succeeded in raising the material's power output density dramatically by using a very hot pressing temperature - up to 1373 Kelvin, or about 2,000 degrees Fahrenheit - to create the material. "The majority of industrial energy input is lost as waste heat," the researchers wrote. "Converting some of the waste heat into useful electrical power will lead to the reduction of fossil fuel consumption and CO2 emission." Thermoelectric materials produce electricity by exploiting the flow of heat current from a warmer area to a cooler area, and their efficiency is calculated as the measure of how well the material converts heat - often waste heat generated by power plants or other industrial processes - into power. For example, a material that takes in 100 watts of heat and produces 10 watts of electricity has an efficiency rate of 10 percent. That's the traditional way of considering thermoelectric materials, said Zhifeng Ren, MD Anderson Professor of Physics at the University of Houston and lead author of the paper. But having a relatively high conversion efficiency doesn't guarantee a high power output, which measures the amount of power produced by the material rather than the rate of the conversion. Because waste heat is an abundant - and free - source of fuel, the conversion rate is less important than the total amount of power that can be produced, said Ren, who is also a principal investigator at the Texas Center for Superconductivity at UH. "In the past, that has not been emphasized." In addition to Ren, researchers involved in the project include Ran He, Jun Mao, Qing Jie, Jing Shuai, Hee Seok Kim, Yuan Liu and Paul C.W. Chu, all of UH; Daniel Kraemer, Lingping Zeng and Gang Chen of the Massachusetts Institute of Technology; Yucheng Lan of Morgan State University, and Chunhua Li and David Broido of Boston College. The researchers tweaked a compound made up of niobium, iron and antimony, replacing between 4 and 5 percent of the niobium with titanium. Processing the new compound at a variety of high temperatures suggested that a very high temperature - 1373 Kelvin - resulted in a material with an unusually high power factor. "For most thermoelectric materials, a power factor of 40 is good," Ren said. "Many have a power factor of 20 or 30." The new material has a power factor of 106 at room temperature, and researchers were able to demonstrate an output power density of 22 watts per square centimeter, far higher than the 5 to 6 watts typically produced, he said. "This aspect of thermoelectrics needs to be emphasized," he said. "You can't just look at the efficiency. You have to look also at the power factor and power output."


News Article | November 16, 2016
Site: www.sciencedaily.com

With energy conservation expected to play a growing role in managing global demand, materials and methods that make better use of existing sources of energy have become increasingly important. Researchers reported this week in the Proceedings of the National Academy of Sciences that they have demonstrated a step forward in converting waste heat -- from industrial smokestacks, power generating plants or even automobile tailpipes -- into electricity. The work, using a thermoelectric compound composed of niobium, titanium, iron and antimony, succeeded in raising the material's power output density dramatically by using a very hot pressing temperature -- up to 1373 Kelvin, or about 2,000 degrees Fahrenheit -- to create the material. "The majority of industrial energy input is lost as waste heat," the researchers wrote. "Converting some of the waste heat into useful electrical power will lead to the reduction of fossil fuel consumption and CO2 emission." Thermoelectric materials produce electricity by exploiting the flow of heat current from a warmer area to a cooler area, and their efficiency is calculated as the measure of how well the material converts heat -- often waste heat generated by power plants or other industrial processes -- into power. For example, a material that takes in 100 watts of heat and produces 10 watts of electricity has an efficiency rate of 10 percent. That's the traditional way of considering thermoelectric materials, said Zhifeng Ren, MD Anderson Professor of Physics at the University of Houston and lead author of the paper. But having a relatively high conversion efficiency doesn't guarantee a high power output, which measures the amount of power produced by the material rather than the rate of the conversion. Because waste heat is an abundant -- and free -- source of fuel, the conversion rate is less important than the total amount of power that can be produced, said Ren, who is also a principal investigator at the Texas Center for Superconductivity at UH. "In the past, that has not been emphasized." In addition to Ren, researchers involved in the project include Ran He, Jun Mao, Qing Jie, Jing Shuai, Hee Seok Kim, Yuan Liu and Paul C.W. Chu, all of UH; Daniel Kraemer, Lingping Zeng and Gang Chen of the Massachusetts Institute of Technology; Yucheng Lan of Morgan State University, and Chunhua Li and David Broido of Boston College. The researchers tweaked a compound made up of niobium, iron and antimony, replacing between 4 and 5 percent of the niobium with titanium. Processing the new compound at a variety of high temperatures suggested that a very high temperature -- 1373 Kelvin -- resulted in a material with an unusually high power factor. "For most thermoelectric materials, a power factor of 40 is good," Ren said. "Many have a power factor of 20 or 30." The new material has a power factor of 106 at room temperature, and researchers were able to demonstrate an output power density of 22 watts per square centimeter, far higher than the 5 to 6 watts typically produced, he said. "This aspect of thermoelectrics needs to be emphasized," he said. "You can't just look at the efficiency. You have to look also at the power factor and power output."


News Article | October 3, 2016
Site: www.cemag.us

Researchers at the University of Houston and Massachusetts Institute of Technology have reported a substantial advance in generating electricity through a combination of concentrating solar power and thermoelectric materials. By combining concentrating solar power — which converts light into heat that is then used to generate electricity — with segmented thermoelectric legs, made up of two different thermoelectric materials, each working at different temperature ranges, researchers said they have demonstrated a promising new alternative solar energy technology. Their findings are published in Nature Energy. Zhifeng Ren, MD Anderson Professor of physics at the University of Houston and an author of the paper, says the work illustrates a new low-cost, nontoxic way to generate power. While it’s not intended to replace large-scale power plants, it could prove especially useful for isolated areas that aren’t on a traditional electric grid, powering small clusters of homes or businesses, for example, he said. In addition to generating electricity, the technology also can produce hot water — valuable for both private and industrial purposes. In addition to Ren, other authors on the paper include Gang Chen, Daniel Kraemer, Kenneth McEnaney, Lee A. Weinstein, and James Loomis, all of MIT, and UH researchers Qing Jie, Feng Cao, and Weishu Liu. Ren, who also is a principal investigator at the Texas Center for Superconductivity at UH, says the work draws on the researchers’ earlier work, which demonstrated proof of the concept. For this project, supported in part by the Department of Energy, they actually built a device to measure how well optical concentration worked to improve the overall system efficiency. They demonstrated an efficiency of 7.4 percent but reported that based upon their calculations, the device could achieve an efficiency of 9.6 percent. Their previous work resulted in an efficiency of 4.6 percent. “The performance improvement is achieved by the use of segmented thermoelectric legs, a high-temperature spectrally selective solar absorber enabling stable vacuum operation with absorber temperatures up to 600 (degrees) C, and combining optical and thermal concentration,” the researchers wrote. “Our work suggests that concentrating STEGs (solar thermoelectric generators) have the potential to become a promising alternative energy technology.” To gain the higher efficiency, the researchers used a solar absorber, boosted by optical concentrators to increase the heat and improve the energy density. The absorber was placed on legs constructed of thermoelectric materials. While their previous work used only bismuth telluride — a well-known thermoelectric material — this version used skudderudite for the top half of the legs and bismuth telluride for the lower half. Thermoelectric materials produce electricity by exploiting the flow of heat current from a warmer area to a cooler area. By using two materials, the researchers said they were able to take advantage of a broader range of temperatures produced by the solar absorber and boost generating efficiency. Skutterudite, for example, performs best at temperatures above 200 degrees Centigrade, while bismuth telluride works optimally at temperatures below that level. “The record-high efficiencies are achieved by segmenting two thermoelectric materials, skutterudite and bismuth telluride, coupled to a spectrally selective surface operated at close to 600 (degrees) C by combined optical and thermal concentration of the sunlight,” they wrote.


News Article | October 3, 2016
Site: www.rdmag.com

Researchers at the University of Houston and Massachusetts Institute of Technology have reported a substantial advance in generating electricity through a combination of concentrating solar power and thermoelectric materials. By combining concentrating solar power – which converts light into heat that is then used to generate electricity – with segmented thermoelectric legs, made up of two different thermoelectric materials, each working at different temperature ranges, researchers said they have demonstrated a promising new alternative solar energy technology. Their findings are published in Nature Energy. Zhifeng Ren, MD Anderson Professor of physics at the University of Houston and an author of the paper, said the work illustrates a new low-cost, nontoxic way to generate power. While it’s not intended to replace large-scale power plants, it could prove especially useful for isolated areas that aren’t on a traditional electric grid, powering small clusters of homes or businesses, for example, he said. In addition to generating electricity, the technology also can produce hot water – valuable for both private and industrial purposes. In addition to Ren, other authors on the paper include Gang Chen, Daniel Kraemer, Kenneth McEnaney, Lee A. Weinstein and James Loomis, all of MIT, and UH researchers Qing Jie, Feng Cao and Weishu Liu. Ren, who also is a principal investigator at the Texas Center for Superconductivity at UH, said the work draws on the researchers’ earlier work, which demonstrated proof of the concept. For this project, supported in part by the Department of Energy, they actually built a device to measure how well optical concentration worked to improve the overall system efficiency. They demonstrated an efficiency of 7.4 percent but reported that based upon their calculations, the device could achieve an efficiency of 9.6 percent. Their previous work resulted in an efficiency of 4.6 percent. “The performance improvement is achieved by the use of segmented thermoelectric legs, a high-temperature spectrally selective solar absorber enabling stable vacuum operation with absorber temperatures up to 600 (degrees) C, and combining optical and thermal concentration,” the researchers wrote. “Our work suggests that concentrating STEGs (solar thermoelectric generators) have the potential to become a promising alternative energy technology.” To gain the higher efficiency, the researchers used a solar absorber, boosted by optical concentrators to increase the heat and improve the energy density. The absorber was placed on legs constructed of thermoelectric materials. While their previous work used only bismuth telluride – a well-known thermoelectric material – this version used skudderudite for the top half of the legs and bismuth telluride for the lower half. Thermoelectric materials produce electricity by exploiting the flow of heat current from a warmer area to a cooler area. By using two materials, the researchers said they were able to take advantage of a broader range of temperatures produced by the solar absorber and boost generating efficiency. Skutterudite, for example, performs best at temperatures above 200 degrees Centigrade, while bismuth telluride works optimally at temperatures below that level. “The record-high efficiencies are achieved by segmenting two thermoelectric materials, skutterudite and bismuth telluride, coupled to a spectrally selective surface operated at close to 600 (degrees) C by combined optical and thermal concentration of the sunlight,” they wrote.


News Article | November 1, 2016
Site: www.sciencedaily.com

Researchers at the University of Houston have reported a new method for inducing superconductivity in non-superconducting materials, demonstrating a concept proposed decades ago but never proven. The technique can also be used to boost the efficiency of known superconducting materials, suggesting a new way to advance the commercial viability of superconductors, said Paul C.W. Chu, chief scientist at the Texas Center for Superconductivity at UH (TcSUH) and corresponding author of a paper describing the work, published Oct. 31 in the Proceedings of the National Academy of Sciences. "Superconductivity is used in many things, of which MRI (magnetic resonance imaging) is perhaps the best known," said Chu, the physicist who holds the TLL Temple Chair of Science at UH. But the technology used in health care, utilities and other fields remains expensive, in part because it requires expensive cooling, which has limited widespread adoption, he said. The research, demonstrating a new method to take advantage of assembled interfaces to induce superconductivity in the non-superconducting compound calcium iron arsenide, offers a new approach to finding superconductors that work at higher temperatures. Superconducting materials conduct electric current without resistance, while traditional transmission materials lose as much as 10 percent of energy between the generating source and the end user. That means superconductors could allow utility companies to provide more electricity without increasing the amount of fuel used to generate electricity. "One way that has long been proposed to achieve enhanced T s (critical temperature, or the temperature at which a material becomes superconducting) is to take advantage of artificially or naturally assembled interfaces," the researchers wrote. "The present work clearly demonstrates that high T superconductivity in the well-known non-superconducting compound CaFe As (calcium iron arsenide) can be induced by antiferromagnetic/metallic layer stacking and provides the most direct evidence to date for the interface-enhanced T in this compound." Chu's coauthors on the paper include lead author Kui Zhao, a recent UH graduate now at Advanced MicroFabrication Equipment Inc. in Shanghai; Liangzi Deng, Shu-Yuan Huyan and Yu-Yi Xue, both affiliated with the UH Department of Physics and TcSUH, and Bing Lv, a material physicist who recently moved to the University of Texas-Dallas. The concept that superconductivity could be induced or enhanced at the point where two different materials come together -- the interface -- was first proposed in the 1970s but had never been conclusively demonstrated, Chu said. Some previous experiments showing enhanced superconducting critical temperature could not exclude other effects due to stress or chemical doping, which prevented verification, he said. To validate the concept, researchers working in ambient pressure exposed the undoped calcium iron arsenide compound to heat -- 350 degrees Centigrade, considered relatively low temperature for this procedure -- in a process known as annealing. The compound formed two distinct phases, with one phase increasingly converted to the other the longer the sample was annealed. Chu said neither of the two phases was superconducting, but researchers were able to detect superconductivity at the point when the two phases coexist. Although the superconducting critical temperature of the sample produced through the process was still relatively low, Chu said the method used to prove the concept offers a new direction in the search for more efficient, less expensive superconducting materials.


News Article | November 7, 2016
Site: www.materialstoday.com

Researchers at the University of Houston (UH) have reported a new method for inducing superconductivity in non-superconducting materials, demonstrating a concept proposed decades ago but never proven. This technique could also be used to boost the efficiency of known superconducting materials, suggesting a new way to advance the commercial viability of superconductors, said Paul Chu, chief scientist at the Texas Center for Superconductivity at UH (TcSUH) and corresponding author of a paper on the work in the Proceedings of the National Academy of Sciences. "Superconductivity is used in many things, of which MRI (magnetic resonance imaging) is perhaps the best known," said Chu. But the technology used in health care and other fields remains costly, in part because it requires expensive cooling, which has limited widespread adoption. In this work, Chu and his colleagues demonstrate a new method for taking advantage of assembled interfaces to induce superconductivity in the non-superconducting compound calcium iron arsenide, thereby offering a new approach to finding superconductors that work at higher temperatures. Superconducting materials conduct electric current without resistance, while traditional materials can lose as much as 10% of the energy being transmitted between the generating source and the end user. That means superconductors could allow utility companies to provide more electricity without increasing the amount of fuel used to generate the electricity. "One way that has long been proposed to achieve enhanced Tcs (critical temperature, or the temperature at which a material becomes superconducting) is to take advantage of artificially or naturally assembled interfaces," the researchers write in the paper. "The present work clearly demonstrates that high Tc superconductivity in the well-known non-superconducting compound CaFe As (calcium iron arsenide) can be induced by antiferromagnetic/metallic layer stacking and provides the most direct evidence to date for the interface-enhanced Tc in this compound." The concept that superconductivity could be induced or enhanced at the point where two different materials come together – the interface – was first proposed in the 1970s but had never been conclusively demonstrated, Chu said. Some previous experiments showing enhanced Tcs could not exclude the influence of other effects such as stress or chemical doping, which prevented verification, he said. To validate the concept, researchers working at ambient pressures exposed the undoped calcium iron arsenide compound to a relatively low temperature of 350°C, in a process known as annealing. This caused the compound to form two distinct phases, with one phase increasingly converted to the other the longer the sample was annealed. Although neither of the two phases was superconducting, Chu and his colleagues were able to detect superconductivity at the point when the two phases coexist. Although the Tcs of the sample produced through this process was still relatively low, Chu said the method used to prove the concept offers a new direction in the search for more efficient, less expensive superconducting materials. This story is adapted from material from the University of Houston, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.


News Article | October 31, 2016
Site: www.eurekalert.org

Researchers at the University of Houston have reported a new method for inducing superconductivity in non-superconducting materials, demonstrating a concept proposed decades ago but never proven. The technique can also be used to boost the efficiency of known superconducting materials, suggesting a new way to advance the commercial viability of superconductors, said Paul C.W. Chu, chief scientist at the Texas Center for Superconductivity at UH (TcSUH) and corresponding author of a paper describing the work, published Oct. 31 in the Proceedings of the National Academy of Sciences. "Superconductivity is used in many things, of which MRI (magnetic resonance imaging) is perhaps the best known," said Chu, the physicist who holds the TLL Temple Chair of Science at UH. But the technology used in health care, utilities and other fields remains expensive, in part because it requires expensive cooling, which has limited widespread adoption, he said. The research, demonstrating a new method to take advantage of assembled interfaces to induce superconductivity in the non-superconducting compound calcium iron arsenide, offers a new approach to finding superconductors that work at higher temperatures. Superconducting materials conduct electric current without resistance, while traditional transmission materials lose as much as 10 percent of energy between the generating source and the end user. That means superconductors could allow utility companies to provide more electricity without increasing the amount of fuel used to generate electricity. "One way that has long been proposed to achieve enhanced Tcs (critical temperature, or the temperature at which a material becomes superconducting) is to take advantage of artificially or naturally assembled interfaces," the researchers wrote. "The present work clearly demonstrates that high Tc superconductivity in the well-known non-superconducting compound CaFe2As2 (calcium iron arsenide) can be induced by antiferromagnetic/metallic layer stacking and provides the most direct evidence to date for the interface-enhanced Tc in this compound." Chu's coauthors on the paper include lead author Kui Zhao, a recent UH graduate now at Advanced MicroFabrication Equipment Inc. in Shanghai; Liangzi Deng, Shu-Yuan Huyan and Yu-Yi Xue, both affiliated with the UH Department of Physics and TcSUH, and Bing Lv, a material physicist who recently moved to the University of Texas-Dallas. The concept that superconductivity could be induced or enhanced at the point where two different materials come together - the interface - was first proposed in the 1970s but had never been conclusively demonstrated, Chu said. Some previous experiments showing enhanced superconducting critical temperature could not exclude other effects due to stress or chemical doping, which prevented verification, he said. To validate the concept, researchers working in ambient pressure exposed the undoped calcium iron arsenide compound to heat - 350 degrees Centigrade, considered relatively low temperature for this procedure - in a process known as annealing. The compound formed two distinct phases, with one phase increasingly converted to the other the longer the sample was annealed. Chu said neither of the two phases was superconducting, but researchers were able to detect superconductivity at the point when the two phases coexist. Although the superconducting critical temperature of the sample produced through the process was still relatively low, Chu said the method used to prove the concept offers a new direction in the search for more efficient, less expensive superconducting materials.


Home > Press > Physicists induce superconductivity in non-superconducting materials: Novel method also can improve efficiency in known superconducting materials Abstract: Researchers at the University of Houston have reported a new method for inducing superconductivity in non-superconducting materials, demonstrating a concept proposed decades ago but never proven. The technique can also be used to boost the efficiency of known superconducting materials, suggesting a new way to advance the commercial viability of superconductors, said Paul C.W. Chu, chief scientist at the Texas Center for Superconductivity at UH (TcSUH) and corresponding author of a paper describing the work, published Oct. 31 in the Proceedings of the National Academy of Sciences. "Superconductivity is used in many things, of which MRI (magnetic resonance imaging) is perhaps the best known," said Chu, the physicist who holds the TLL Temple Chair of Science at UH. But the technology used in health care, utilities and other fields remains expensive, in part because it requires expensive cooling, which has limited widespread adoption, he said. The research, demonstrating a new method to take advantage of assembled interfaces to induce superconductivity in the non-superconducting compound calcium iron arsenide, offers a new approach to finding superconductors that work at higher temperatures. Superconducting materials conduct electric current without resistance, while traditional transmission materials lose as much as 10 percent of energy between the generating source and the end user. That means superconductors could allow utility companies to provide more electricity without increasing the amount of fuel used to generate electricity. "One way that has long been proposed to achieve enhanced Tcs (critical temperature, or the temperature at which a material becomes superconducting) is to take advantage of artificially or naturally assembled interfaces," the researchers wrote. "The present work clearly demonstrates that high Tc superconductivity in the well-known non-superconducting compound CaFe2As2 (calcium iron arsenide) can be induced by antiferromagnetic/metallic layer stacking and provides the most direct evidence to date for the interface-enhanced Tc in this compound." Chu's coauthors on the paper include lead author Kui Zhao, a recent UH graduate now at Advanced MicroFabrication Equipment Inc. in Shanghai; Liangzi Deng, Shu-Yuan Huyan and Yu-Yi Xue, both affiliated with the UH Department of Physics and TcSUH, and Bing Lv, a material physicist who recently moved to the University of Texas-Dallas. The concept that superconductivity could be induced or enhanced at the point where two different materials come together - the interface - was first proposed in the 1970s but had never been conclusively demonstrated, Chu said. Some previous experiments showing enhanced superconducting critical temperature could not exclude other effects due to stress or chemical doping, which prevented verification, he said. To validate the concept, researchers working in ambient pressure exposed the undoped calcium iron arsenide compound to heat - 350 degrees Centigrade, considered relatively low temperature for this procedure - in a process known as annealing. The compound formed two distinct phases, with one phase increasingly converted to the other the longer the sample was annealed. Chu said neither of the two phases was superconducting, but researchers were able to detect superconductivity at the point when the two phases coexist. Although the superconducting critical temperature of the sample produced through the process was still relatively low, Chu said the method used to prove the concept offers a new direction in the search for more efficient, less expensive superconducting materials. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | October 31, 2016
Site: phys.org

The technique can also be used to boost the efficiency of known superconducting materials, suggesting a new way to advance the commercial viability of superconductors, said Paul C.W. Chu, chief scientist at the Texas Center for Superconductivity at UH (TcSUH) and corresponding author of a paper describing the work, published Oct. 31 in the Proceedings of the National Academy of Sciences. "Superconductivity is used in many things, of which MRI (magnetic resonance imaging) is perhaps the best known," said Chu, the physicist who holds the TLL Temple Chair of Science at UH. But the technology used in health care, utilities and other fields remains expensive, in part because it requires expensive cooling, which has limited widespread adoption, he said. The research, demonstrating a new method to take advantage of assembled interfaces to induce superconductivity in the non-superconducting compound calcium iron arsenide, offers a new approach to finding superconductors that work at higher temperatures. Superconducting materials conduct electric current without resistance, while traditional transmission materials lose as much as 10 percent of energy between the generating source and the end user. That means superconductors could allow utility companies to provide more electricity without increasing the amount of fuel used to generate electricity. "One way that has long been proposed to achieve enhanced Tcs (critical temperature, or the temperature at which a material becomes superconducting) is to take advantage of artificially or naturally assembled interfaces," the researchers wrote. "The present work clearly demonstrates that high Tc superconductivity in the well-known non-superconducting compound CaFe2As2 (calcium iron arsenide) can be induced by antiferromagnetic/metallic layer stacking and provides the most direct evidence to date for the interface-enhanced Tc in this compound." Chu's coauthors on the paper include lead author Kui Zhao, a recent UH graduate now at Advanced MicroFabrication Equipment Inc. in Shanghai; Liangzi Deng, Shu-Yuan Huyan and Yu-Yi Xue, both affiliated with the UH Department of Physics and TcSUH, and Bing Lv, a material physicist who recently moved to the University of Texas-Dallas. The concept that superconductivity could be induced or enhanced at the point where two different materials come together - the interface - was first proposed in the 1970s but had never been conclusively demonstrated, Chu said. Some previous experiments showing enhanced superconducting critical temperature could not exclude other effects due to stress or chemical doping, which prevented verification, he said. To validate the concept, researchers working in ambient pressure exposed the undoped calcium iron arsenide compound to heat - 350 degrees Centigrade, considered relatively low temperature for this procedure - in a process known as annealing. The compound formed two distinct phases, with one phase increasingly converted to the other the longer the sample was annealed. Chu said neither of the two phases was superconducting, but researchers were able to detect superconductivity at the point when the two phases coexist. Although the superconducting critical temperature of the sample produced through the process was still relatively low, Chu said the method used to prove the concept offers a new direction in the search for more efficient, less expensive superconducting materials. Explore further: Finding superconducting needles in the metal haystack More information: Interface-induced superconductivity at ∼25 K at ambient pressure in undoped CaFe2As2 single crystals, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1616264113

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