Ferroelectric materials have enormous potential applications in advanced techniques. However, there are still many problems in its practical application. Dielectric and mechanical (internal friction) measurements are ...Ferroelectric materials have enormous potential applications in advanced techniques. However, there are still many problems in its practical application. Dielectric and mechanical (internal friction) measurements are very sensitive to phase transitions, relaxation process of point defects, domain walls and their mobility, which have severe effect on ferroelectric properties. These make them become very good means to investigate substantial information on structural features and to explore the fundamental principles in ferroelectric materials and their applications. In this paper, the dielectric and internal friction measurement were used to investigate the behaviors for point defects and phase transition in ferroelectric ceramics such as Bi_ 4-x La_ x Ti_ 3 O_ 12 , Bi_ 4 Ti_ 3-y Nb_ y O_ 12 , SrBi_ 2 Ti_ 2 O_ 9 , PbZr_ x Ti_ 1-x O_ 3 ,_ PMN-PT. They were used to clarify the mechanism for some ferroelectric behaviors.展开更多
The low-temperature magnetoresistance (LTMR) in hydrothermally synthesized La 0.98 Ca 0.02 MnO 3- δ / γ -Mn 2O 3 granular system was investigated. As-prepared powders are amorphous except for a small amount of cryst...The low-temperature magnetoresistance (LTMR) in hydrothermally synthesized La 0.98 Ca 0.02 MnO 3- δ / γ -Mn 2O 3 granular system was investigated. As-prepared powders are amorphous except for a small amount of crystalline phase LaCO 3OH. After sintered at 1 073 K or above, La 0.98 Ca 0.02 MnO 3- δ perovskite and secondary phase γ -Mn 2O 3 coexist. A large LTMR of ～65% at 127 K and ～50% at 0 K in the sample with mean grain size of 23 nm was observed. The observation of a large magnetoresistance over a wide temperature interval could be of importance for useful applications.展开更多
文摘Ferroelectric materials have enormous potential applications in advanced techniques. However, there are still many problems in its practical application. Dielectric and mechanical (internal friction) measurements are very sensitive to phase transitions, relaxation process of point defects, domain walls and their mobility, which have severe effect on ferroelectric properties. These make them become very good means to investigate substantial information on structural features and to explore the fundamental principles in ferroelectric materials and their applications. In this paper, the dielectric and internal friction measurement were used to investigate the behaviors for point defects and phase transition in ferroelectric ceramics such as Bi_ 4-x La_ x Ti_ 3 O_ 12 , Bi_ 4 Ti_ 3-y Nb_ y O_ 12 , SrBi_ 2 Ti_ 2 O_ 9 , PbZr_ x Ti_ 1-x O_ 3 ,_ PMN-PT. They were used to clarify the mechanism for some ferroelectric behaviors.
文摘The low-temperature magnetoresistance (LTMR) in hydrothermally synthesized La 0.98 Ca 0.02 MnO 3- δ / γ -Mn 2O 3 granular system was investigated. As-prepared powders are amorphous except for a small amount of crystalline phase LaCO 3OH. After sintered at 1 073 K or above, La 0.98 Ca 0.02 MnO 3- δ perovskite and secondary phase γ -Mn 2O 3 coexist. A large LTMR of ～65% at 127 K and ～50% at 0 K in the sample with mean grain size of 23 nm was observed. The observation of a large magnetoresistance over a wide temperature interval could be of importance for useful applications.
