La/Mn co-doped Bi4Ti3O12 ceramics, Bi3.25La0.75Ti3-xMnxO12 （x = 0.02, 0.04, 0.06, 0.08）, were prepared by the solid-state reaction method. The influence of manganese substitution for the titanium part in Bi3.25La0.7...La/Mn co-doped Bi4Ti3O12 ceramics, Bi3.25La0.75Ti3-xMnxO12 （x = 0.02, 0.04, 0.06, 0.08）, were prepared by the solid-state reaction method. The influence of manganese substitution for the titanium part in Bi3.25La0.75Ti3O12 on the sintering behaviour, microstructure, Raman spectra and electrical properties was investigated. The experimental results show that the phase composition of all samples with and without manganese doping, sintered at 1000 ℃, consists of a single phase with a bismuth-layered structure belonging to the crystalline phase Bi4Ti3O12. There is no evidence of any impurity phase, but a small change in crystallographic orientation is observed. The Curie temperature of Bi3.25La0.75Ti3-xMnxO12 ceramics is steadily shifted to lower temperature with increasing Mn-doping content. Moreover, the remnant polarisation （Pr） of Bi3.25La0.75Ti3- xMnxO12 samples increases with Mn-doping content, and the Bi3.25La0.75Ti2.92Mn0.08O12 sample exhibits the largest Pr of 16.6 μC/cm^2.展开更多
Ferroelectric Bi2.9Pr0.9Ti3O12/La0.67Sr0.33MnO3 （BPT/LSMO） films are fabricated on Pt（111）/TiO2/SiO2/Si substrates by rf-magnetron sputtering method. The influences of the LSMO deposition conditions and LSMO layer...Ferroelectric Bi2.9Pr0.9Ti3O12/La0.67Sr0.33MnO3 （BPT/LSMO） films are fabricated on Pt（111）/TiO2/SiO2/Si substrates by rf-magnetron sputtering method. The influences of the LSMO deposition conditions and LSMO layer thickness on properties of BPT thin films are studied. The LSMO layer deposited at 300℃ and 450℃ favours preferred （117） orientation of BPT films, while deposited at 600℃ for LSMO layer leads to strong （111）- preferred orientation of BPT film. With the LSMO buffer layer, the films exhibit improved ferroelectric properties and Pt/BPT/LSMO（2Onm）/Pt capacitor shows the largest remnant polarization Pr of 18.4 μC/cm^2 at 14 V. A similar change in dielectric constant with the increase of LSMO layer thickness is also observed and the highest dielectric constant of 342. 7 is obtained for the Pt/BPT/LSMO（20 nm）/Pt film. Compared with the Pt/BPT/Pt film, the Pt/BPT/LSMO/Pt films exhibit better fatigue endurance after 5 × 10^9 switching cycles. Moreover, the LSMO layer has apparent effect on leakage current density and the Pt/BPT/LSMO（20 nm）/Pt film exhibits the lowest leakage current density.展开更多
The effect of pyrolysis atmosphere is investigated for Bi3.25 La0.75 Ti3O12 （BLT） films prepared on Pt/TiO2/SiO2/p-Si（100substrates by sol-gel processes. The pyrolysis is carried out at 400℃ for 20 min under air o...The effect of pyrolysis atmosphere is investigated for Bi3.25 La0.75 Ti3O12 （BLT） films prepared on Pt/TiO2/SiO2/p-Si（100substrates by sol-gel processes. The pyrolysis is carried out at 400℃ for 20 min under air or O2 atmosphere and the successive anneal is performed at 700℃ for 30min under O2 atmosphere. The pyrolysis under O2 is enough for complete removal of organic species, however after pyrolysis under air, carbon and hydrogen atomic species as organic fragment are partly remained in the film. This incomplete removal of organic fragments affects the grain growth and cause more defects in the film or between interfaces during the annealing for the crystallization of BLT film. The growth direction and grain size of the BLT film is revealed to affect ferroelectric properties. The remanent polarization PTfor the BLT films of pyrolysis in O2 and air are measured to be 18.85μC/cm^2 and 12.56μC/cm^2,respectively. The defects degrade the fatigue property dramatically for the film of pyrolysis in air. It can be concluded that the pyrolysis is an important procedure to control ferroeleetrie properties.展开更多
基金Project supported by the National Science Fund for Distinguished Young Scholars (Grant No. 50625204)National Natural Science Fund for Creative Research Groups (Grant No. 50621201)+2 种基金the Ministry of Science and Technology of China through National Basic Research Program of China (Grant No. 2009CB623301)through National High Technology ResearchDevelopment Program of China (Grant No. 2006AA03Z428)
文摘La/Mn co-doped Bi4Ti3O12 ceramics, Bi3.25La0.75Ti3-xMnxO12 （x = 0.02, 0.04, 0.06, 0.08）, were prepared by the solid-state reaction method. The influence of manganese substitution for the titanium part in Bi3.25La0.75Ti3O12 on the sintering behaviour, microstructure, Raman spectra and electrical properties was investigated. The experimental results show that the phase composition of all samples with and without manganese doping, sintered at 1000 ℃, consists of a single phase with a bismuth-layered structure belonging to the crystalline phase Bi4Ti3O12. There is no evidence of any impurity phase, but a small change in crystallographic orientation is observed. The Curie temperature of Bi3.25La0.75Ti3-xMnxO12 ceramics is steadily shifted to lower temperature with increasing Mn-doping content. Moreover, the remnant polarisation （Pr） of Bi3.25La0.75Ti3- xMnxO12 samples increases with Mn-doping content, and the Bi3.25La0.75Ti2.92Mn0.08O12 sample exhibits the largest Pr of 16.6 μC/cm^2.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50272022, 90407023 and 10604017.
文摘Ferroelectric Bi2.9Pr0.9Ti3O12/La0.67Sr0.33MnO3 （BPT/LSMO） films are fabricated on Pt（111）/TiO2/SiO2/Si substrates by rf-magnetron sputtering method. The influences of the LSMO deposition conditions and LSMO layer thickness on properties of BPT thin films are studied. The LSMO layer deposited at 300℃ and 450℃ favours preferred （117） orientation of BPT films, while deposited at 600℃ for LSMO layer leads to strong （111）- preferred orientation of BPT film. With the LSMO buffer layer, the films exhibit improved ferroelectric properties and Pt/BPT/LSMO（2Onm）/Pt capacitor shows the largest remnant polarization Pr of 18.4 μC/cm^2 at 14 V. A similar change in dielectric constant with the increase of LSMO layer thickness is also observed and the highest dielectric constant of 342. 7 is obtained for the Pt/BPT/LSMO（20 nm）/Pt film. Compared with the Pt/BPT/Pt film, the Pt/BPT/LSMO/Pt films exhibit better fatigue endurance after 5 × 10^9 switching cycles. Moreover, the LSMO layer has apparent effect on leakage current density and the Pt/BPT/LSMO（20 nm）/Pt film exhibits the lowest leakage current density.
基金Supported by Key Project of the National Natural Science Foundation of China under Grant No 90407023.
文摘The effect of pyrolysis atmosphere is investigated for Bi3.25 La0.75 Ti3O12 （BLT） films prepared on Pt/TiO2/SiO2/p-Si（100substrates by sol-gel processes. The pyrolysis is carried out at 400℃ for 20 min under air or O2 atmosphere and the successive anneal is performed at 700℃ for 30min under O2 atmosphere. The pyrolysis under O2 is enough for complete removal of organic species, however after pyrolysis under air, carbon and hydrogen atomic species as organic fragment are partly remained in the film. This incomplete removal of organic fragments affects the grain growth and cause more defects in the film or between interfaces during the annealing for the crystallization of BLT film. The growth direction and grain size of the BLT film is revealed to affect ferroelectric properties. The remanent polarization PTfor the BLT films of pyrolysis in O2 and air are measured to be 18.85μC/cm^2 and 12.56μC/cm^2,respectively. The defects degrade the fatigue property dramatically for the film of pyrolysis in air. It can be concluded that the pyrolysis is an important procedure to control ferroeleetrie properties.
