Na_(0.25)K_(0.25)Bi_(0.5)TiO_3无铅压电陶瓷的介电特性研究

Dielectric properties of Na_(0.25)K_(0.25)Bi_(0.5)TiO_3 lead-free ceramics

用固相反应法制备了Na_(0.25)K_(0.25)Bi_(0.5)TiO_3(NKBT50)陶瓷,研究了该陶瓷在室温至400℃温度范围内的介电性能.发现该陶瓷的介电温谱与烧结气氛、极化状态有关.在空气中烧结的未极化样品在70℃附近存在介电和损耗峰,而极化后及在氧气氛中烧结的样品并不存在该介电、损耗峰.分析认为70℃的介电和损耗峰与氧空位形成的缺陷偶极子的极化弛豫有关.热激电流显示,陶瓷的去极化温度为225℃,与此相对应的介电、损耗峰也与氧空位有关.

Na0.25K0.25Bi0.5TiO3 （NKBT50）lead-free ceramics were prepared by solid-state reaction. The dielectric property of the ceramics was invesiigated in the lemperature range from room temperature to 400℃. Our results show that there exists a dielectric anomaly in the vicinity of 70℃ for the unpeled ceramics sintered in air, which will disappear after the ceramic were poled or sintered in oxygen. It is believed that the dielectric anomaly is caused by defect dipoles related to oxygen vacancies. Thermal stimulated depolarization current shows that the materials are depolarized at 225℃ and the dielectric anomaly corresponding to this phase transition is also affected by oxygen vacancies.