铌钪酸铅-铌镁酸铅-钛酸铅铁电单晶的制备及其高性能机制研究

At present, Pb(Mg1/3Nb2/3)O3-PbTiO3 binary ferroelectric crystals exhibit high piezoelectric properties. However, they cannot meet the demand of high power and high performance transducers, because of their low phase transition temperature and coercive field. So it is urgent to develop new ferroelectric crystals with high properties. Pb(Sc1/2Nb1/2)O3 crystal exhibits high Curie temperature and coercive field, the doping of which into Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solution can not only increase the phase transition temperatures and coercive field, but also maintain good piezoelectric properties, which is meaningful for the development of new ferroelectric crystals with high properties. Therefore, the applicant has carried out part of work on this system and preliminarily verified its improved phase transition temperature and coercive field. This project will study the preparation of Pb(Sc1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ferroelectric crystals and their high efficiency mechanism: prepare high quality Pb(Sc1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals by optimizing the crystal growth technique and the flux system; investigate their electrical properties, phase and domain structures, to establish the structure-function relationship between microscopic structures and macroscopic properties by the crystal field theory analyses and First principles calculations; illuminate the physical mechanism of high phase transition temperature, large coercive field and high piezoelectric activity.

现有铌镁酸铅-钛酸铅弛豫铁电晶体具有优异的压电性能，但由于其低的相变温度和矫顽场，不能满足大功率、高性能换能器的应用需求，急需开发新型高性能铁电材料。本项目基于铌镁酸铅-钛酸铅体系，利用具有高相变温度和高矫顽场的铌钪酸铅体系进行掺杂改性，在保证高压电性能的基础上提高其相变温度和矫顽场，从而达到高性能铁电材料的开发目标。为此，申请人前期对该体系开展了部分工作，初步证实了其改善的相变温度和矫顽场。本项目拟开展铌钪酸铅-铌镁酸铅-钛酸铅高性能铁电晶体制备及其高性能机制研究。针对前期晶体生长的挥发问题，进行助熔剂体系优化和工艺改进，制备高质量单晶。进而研究晶体的相结构和电学特性，构建微观结构和宏观性能的构效关系。结合晶体场理论和第一性原理计算，阐明其高性能的物理机制。

现有铌镁酸铅-钛酸铅弛豫铁电晶体具有优异的压电性能，但由于其低的相变温度和矫顽电场，不能满足大功率、高性能换能器的应用需求，急需开发新型高性能铁电材料。本项目基于铌镁酸铅-钛酸铅体系，利用具有高相变温度和高矫顽场的铌钪酸铅体系进行掺杂改性，在保证高压电性能的基础上提高其相变温度和矫顽场，从而达到高性能铁电材料的开发目标。为此，本项目开展了铌钪酸铅-铌镁酸铅-钛酸铅高性能铁电晶体制备及其高性能机制研究。针对前期晶体生长的挥发问题，进行助熔剂体系优化和工艺改进，确定了PbO和H3BO3摩尔比3：2复合助溶剂体系，进一步筛选出晶体原料与助溶剂原料摩尔比1：7的最佳进料比例，获得了最大尺寸达30×30mm2的铌钪酸铅-铌镁酸铅-钛酸铅晶体。进而研究了晶体的相结构和电学特性，确定了晶体组分对电学性能的调制规律，并通过组分优化，实现了性能提升，其中，矫顽电场最高达6.0kV/cm，相变温度最高达226ºC，压电常数最大为1577pC/N，最大应变约0.59%。进一步结合对晶体畴结构的研究，确定了其良好的压电性能源于大的畴壁密度。本项目关于铌钪酸铅-铌镁酸铅-钛酸铅铁电晶体的研究为高功率压电器件开发提供了重要的材料基础，并且其压电响应的物理机制研究对新型铁电材料探索具有一定的借鉴价值。