Thermal behavior in ferroelectric SrBi₂Ta₂O₉ thin films

Abstract

Specific heat and X-ray diffraction of Bi-layered perovskite SrBi₂Ta₂O₉ and Bi-rich Sr_0.8Bi_2.2Ta₂O₉ thin films prepared by the sol-gel method were measured from room temperature to 800 K. The specific heat of stoichiometric SrBi₂Ta₂O₉ film shows one slight anomaly at 520 K (T_c). In Sr_0.8Bi_2.2Ta₂O₉ films, the ferroelectric T_c shifted to 620 K and an additional shoulder in C_p was observed at 410 K (T*). The X-ray diffraction of Sr_0.8Bi_2.2Ta₂O₉ films showed structural changes at T* and T_c . This evidence suggests the existence of a new intermediate phase in Bi-rich Sr_0.8Bi_2.2Ta₂O₉.

Keywords:

• SBT
• layered perovskite
• specific heat
• thin film
• ferroelectric
• phase transition