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Sahoo P.S.,Betnoti College Betnoti | Panigrahi A.,Dn College | Patri S.K.,Indian Institute of Technology Kharagpur | Choudhary R.N.P.,Indian Institute of Technology Kharagpur
EPJ Applied Physics | Year: 2010

Strontium-substituted barium vanadates, Ba5-xSr xDyTi3V7O30 (x = 0-5), were prepared by a high-temperature sold-state reaction method. The formation of the materials was checked by X-ray diffraction technique. Preliminary structural analyses of the materials exhibit the formation of new compounds in orthorhombic structure. Surface morphology of the compounds was studied by scanning electron microscopy. The effect of Sr on microstructure of the materials has resulted in a modification of the electrical properties. Study of electrical properties using impedance analysis technique exhibit (i) the presence of negative temperature coefficient of resistance behavior, (ii) presence of temperature dependent electrical relaxation phenomena, (iii) evidences of single electrical relaxation attributed to the presence of bulk contribution to the electrical properties, (iv) an enhancement in the barrier to the mobility of charge carriers on Sr-substitution. The effects of Sr in the electrical conductivity as a function of temperature at different frequency are explained in impedance spectrum analyses. © 2010 EDP Sciences.


Sahoo P.S.,Betnoti College Betnoti | Panigrahi A.,Dn College | Patri S.K.,Indian Institute of Technology Kharagpur | Choudhary R.N.P.,Indian Institute of Technology Kharagpur
Journal of Materials Science: Materials in Electronics | Year: 2010

Polycrystalline sample of Ba 5SmTi 3V 7O 30 was prepared by a high-temperature solid-state reaction technique. Structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). X-ray preliminary structural studies reveal that the material has orthorhombic structure at room temperature. Detailed electrical (dielectric and impedance) properties of the material studied by using a complex impedance spectroscopy (CIS) technique in a wide temperature range (33-450 °C) at different frequencies (10 2-10 6 Hz) reveal that the relative dielectric constant of the material increases with rise in temperature and thus bulk has a major contribution to its dielectric and electrical properties. The bulk resistance of the material decreases with rise in temperature exhibiting a typical negative temperature coefficient of resistance (NTCR) behavior. The nature of the temperature variation of conductivity and value of activation energy, suggest that the conduction process is of mixed-type (ionic-polaronic and space charge). The existence of ferroelectricity in the compound was confirmed from polarization study. © 2009 Springer Science+Business Media, LLC.


Sahoo P.S.,Betnoti College Betnoti | Panigrahi A.,Dn College | Patri S.K.,Indian Institute of Technology Kharagpur | Choudhary R.N.P.,Indian Institute of Technology Kharagpur
Central European Journal of Physics | Year: 2010

A polycrystalline sample, Ba3Sr2DyTi3V7O30, with tungsten bronze structure was prepared by a mixed-oxide method at high temperature (950°C). Preliminary structural analysis of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound was studied by scanning electron microscopy. The dielectric anomaly at 321°C may be attributed to the ferro-paraelectric phase transitions. This was also confirmed from the appearance of a hysteresis loop. The nature of variation of the ac conductivity and value of activation energy at different temperature regions, suggest that the conduction process is of mixed-type (i. e., ionic-polaronic and space charge generated from the oxygen ion vacancies). © 2009 Versita Warsaw and Springer-Verlag Berlin Heidelberg.


Sahoo P.S.,Betnoti College Betnoti | Mohanty B.B.,Betnoti College Betnoti
Advanced Materials Letters | Year: 2014

The advent of nanoscience & technology have completely changed the orientation/direction of studies of eco-friendly (lead-free) materials bringing them at the forefront of scientific developments with considerably enhanced physical properties suitable for a wide variety of challenging applications. Barium based ferroelectric materials have gained much importance due to their vast applications as they possess high dielectric constant, non-linear spontaneous polarization, negative temperature coefficient of resistance behavior etc.. All these characteristics stimulated the researchers to replace toxic and hazardous lead based materials by barium based TB materials from industry. Our present research work deals with the synthesis of polycrystalline samples of Ba2Sr3RTi3V7O30 (R = Gd, Sm) by a high temperature solid state reaction technique and a comparative study of the electrical properties of the samples. Preliminary structural (XRD) analyses of these compounds show the formation of single-phase orthorhombic structures at room temperature having average crystallite size of the order of some nanometer for both the compounds. The electrical properties for both the samples are studied in a wide range of temperature (30-500°C) and frequency (100Hz-1MHz). The dielectric properties suggest that both the compounds have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 230 and 313°C for R= Sm and Gd respectively at frequency 100 kHz).The bulk resistance of the materials exhibits negative temperature coefficient of resistance behavior as observed in semiconductors. © 2014 VBRI press.


Mohanty B.B.,Betnoti College Betnoti | Sahoo P.S.,Betnoti College Betnoti | Sahoo M.P.K.,RGU IIIT | Choudhary R.N.P.,ITER
Advanced Materials Letters | Year: 2012

The polycrystalline Ba3Sr2GdTi3V7O30 material of tungsten bronze structural family was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction analysis exhibits the formation of single-phase compound with orthorhombic crystal system. Surface micrograph recorded by scanning electron microscopic (SEM) technique has well defined but non-uniformly distributed grains throughout the surface of the pellet sample. Detailed studies of dielectric properties as a function of temperature (306-773 K) and frequencies (102-106Hz) suggest that the compound has frequency independent diffused dielectric anomaly at a temperature ~620 K which may be related to ferroelectric phase transition which is confirmed from polarization study. The frequency and temperature dependence of impedance property of the material were analyzed using a complex impedance spectroscopy. The Nyquist plots confirmed the presence of grain and grain boundary effect in the material. © 2012 VBRI press.

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