报告题目：Mechanisms of thermal depolarization in
lead-free relaxor ferroelectric composites
报 告 人：Dr. Lalitha Kodumudi Venkataraman, 洪堡学者
Technical University Darmstadt, Germany
主 持 人：许杰 副教授
报告摘要： Lead based ferroelectrics dominate the commercial market due to their exceptional properties, low cost and ease of preparation. In the past two decades, growing concerns of environmental toxicity has resulted in a resurge of research in lead-free material systems. Of the several lead-free systems that have been studied, the lower manufacturing cost and large strains make (1-x)Na1/2Bi1/2TiO3-xBaTiO3 (NBT-xBT) solid solution, a key candidate as a low cost lead-free alternative to lead containing materials. The composites of NBT-xBT as the matrix phase and ZnO as the dispersed phase were prepared by conventional solid state synthesis. An increase in Td of ~40‒60 oC was observed for the composites with NBT-6BT and NBT-9BT. The mismatch in the coefficient of thermal expansion of the constituent phases result in residual thermal stresses in the composites. In the case of NBT-6BT based composites, a ferroelectric long range order was induced, which was also evidenced from Nuclear Magnetic Resonance of sodium (23Na NMR). The results are explained on the basis of residual thermal stress induced depolarization. The results signify the use of composite approach in inducing ferroelectric order and enhancing the thermal stability of lead-free relaxor ferroelectrics in a significant manner.
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