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Lei T.,Chongqing University of Science and Technology | Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Material and Device | Fu C.,Chongqing University of Science and Technology | And 5 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2015

BiFeO3 (short for BFO) thin films with different grain sizes were fabricated via sol–gel spin-coating method. The effects of grain size on leakage behavior, dielectric, ferroelectric, piezoelectric properties and domain structure of BFO thin films have been investigated systematically. The X-ray diffraction results show that BFO thin films are rhombohedral distortion perovskite structure. Compared with the films annealed at 550 °C, the grain size of BFO thin films annealed at 600 °C is larger and the roughness is less, and the crystallinity and purity are higher. The leakage current density of BFO thin films with larger grain size is much lower than that of the films with smaller grain size. It is found that the conduction behavior of BFO thin films with smaller grain size transforms from Ohmic to space-charge-limited current and Fowler–Nordheim tunneling conduction as electric field increases. But there is the only transition from Ohmic conduction to space-charge-limited conduction for the thin films with larger grain size as electric field increase. The room temperature dielectric constant and remnant polarization of BFO thin films with larger grain size are higher than that of the films with smaller grain size. The ferroelectric domain size increases with the increase of grain size so that the ferroelectric polarization in BFO thin films with larger grain size enhances. Moreover, it is found that there are negatively charged “tail to tail” domain wall in BFO thin films with smaller grain size and positively charged “head to head” domain wall in the sample with larger grain size. The majority carriers including positively charged hole or oxygen vacancy assemble on negatively charged “tail to tail” domain wall in p-type BFO thin films with smaller grain size and result in relative higher leakage current. The piezoelectric coefficient of the films with larger grain size is much higher than that of the sample with smaller grain size. © 2015 Springer Science+Business Media New York


Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Material and Device | Fu C.,Chongqing University of Science and Technology | Fu C.,Chongqing Key Laboratory of Nano Micro Composite Material and Device | And 6 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2014

xBaZr0.52Ti0.48O3–(1−x)BiFeO3 (short for xBZT–(1−x)BFO) solid solution ceramics were synthesized by conventional solid state reaction method. The microstructure, dielectric and ferroelectric properties of xBZT–(1−x)BFO (x = 0.2–0.5) solid solution ceramics have been investigated systematically. The XRD results show that the crystal structure of xBZT–(1−x)BFO solid solution ceramics evolves gradually from rhombohedral to tetragonal phase and the lattice parameters increase as BZT content increases. The grain size of xBZT–(1−x)BFO ceramics increases initially to the maximum (x = 0.3) and then decreases with the increase of BZT content. As BZT content increases, the temperature at which the maximum in the dielectric constant appears and the corresponding maximum dielectric constant increase first and then decrease. There is obvious frequency dispersion and diffuse phase transition in xBZT–(1−x)BFO solid solution ceramics, and the dielectric diffuseness is enhanced by a certain amount of BZT. As BZT content increases, the leakage current density of xBZT–(1−x)BFO ceramics increases first and then decreases, while the remnant polarization and coercive field decrease initially by a large margin and then increase. Moreover, the remnant polarization and coercive field decrease as frequency increases. © 2014, Springer Science+Business Media New York.


Lei T.,Chongqing University of Science and Technology | Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Material and Device | Fu C.,Chongqing University of Science and Technology | And 5 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2015

BiFeO3 (short for BFO) thin films with different grain sizes were fabricated via sol–gel spin-coating method. The effects of grain size on leakage behavior, dielectric, ferroelectric, piezoelectric properties and domain structure of BFO thin films have been investigated systematically. The X-ray diffraction results show that BFO thin films are rhombohedral distortion perovskite structure. Compared with the films annealed at 550 °C, the grain size of BFO thin films annealed at 600 °C is larger and the roughness is less, and the crystallinity and purity are higher. The leakage current density of BFO thin films with larger grain size is much lower than that of the films with smaller grain size. It is found that the conduction behavior of BFO thin films with smaller grain size transforms from Ohmic to space-charge-limited current and Fowler–Nordheim tunneling conduction as electric field increases. But there is the only transition from Ohmic conduction to space-charge-limited conduction for the thin films with larger grain size as electric field increase. The room temperature dielectric constant and remnant polarization of BFO thin films with larger grain size are higher than that of the films with smaller grain size. The ferroelectric domain size increases with the increase of grain size so that the ferroelectric polarization in BFO thin films with larger grain size enhances. Moreover, it is found that there are negatively charged “tail to tail” domain wall in BFO thin films with smaller grain size and positively charged “head to head” domain wall in the sample with larger grain size. The majority carriers including positively charged hole or oxygen vacancy assemble on negatively charged “tail to tail” domain wall in p-type BFO thin films with smaller grain size and result in relative higher leakage current. The piezoelectric coefficient of the films with larger grain size is much higher than that of the sample with smaller grain size. © 2015, Springer Science+Business Media New York.

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