Transitions of Domains and Phases in (Bi1/2Na1/2)TiO3–BaTiO3 Ceramics Driven by Composition, Temperature, and E-Field
讲座名称：
Transitions of Domains and Phases in (Bi1/2Na1/2)TiO3–BaTiO3 Ceramics Driven by Composition, Temperature, and E-Field
讲座时间：
2011-05-05
讲座人：
Xiaoli Tan
形式：
校区：
兴庆校区
实践学分：
讲座内容：
应前沿科学技术研究院院长任晓兵教授邀请，美国爱荷华州立大学（Iowa State University）材料领域著名学者Xiaoli Tan教授将于5月5日来我校访问，并将于5月5日下午4点在曲江校区西一楼A306作学术报告。
报告题目：Transitions of Domains and Phases in (Bi1/2Na1/2)TiO3–BaTiO3 Ceramics Driven by Composition, Temperature, and E-Field
报告时间：5月5日下午4点
报告地点：曲江校区西一楼A306
报告摘要：
The structure-property relationship in the unpoled(1-x)(Bi1/2Na1/2)TiO3–xBaTiO3ceramics was studied usingtransmission electron microscopy (TEM)and dielectric characterization. In contrast to the reported phase diagrams determined using poled ceramics, an additional phase regionexhibitingP4bmnanodomainswas revealed at room temperature around the x = 0.06 morphotropic phase boundary, where optimal properties are obtained.In combination with dielectric characterizations, the hot-stage and room-temperature TEM study suggest an excellent structure-property correlation below 250 ºC. The P4bmnanodomains are associated with the“relaxorantiferroelectric” behavior, which is a new concept proposed in this study to describe the unique short-range-orderedantiferroelectricbehavior, while large ferroelectric domains give rise to long-range-ordered ferroelectric behaviors.In contrast to the sharpness of thecorresponding dielectric anomaly, thestructural transition between large ferroelectric domains and P4bmnanodomains occursgradually in a temperature range of several tens of degrees.The results are summarized as an updated phase diagram for unpoled(1-x)(Bi1/2Na1/2)TiO3–xBaTiO3 ceramics.
The 0.93(Bi1/2Na1/2)TiO3–0.07BaTiO3ceramic was further investigated with the E-field in situ TEM technique. The transition of the nanodomains of the relaxorantiferroelectricP4bm phase to the lamellar microdomains of the ferroelectric P4mm phase was revealed for the first time. When the applied field increased further, the coalescence of lamellar microdomains into a huge P4mm domain was also recorded. Our results directly confirmed the occurrence of an E-field induced phase transition during the poling process in morphotropic phase boundary compositions of the (1-x)(Bi1/2Na1/2)TiO3–xBaTiO3 lead-free piezoceramics.
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