铌酸钾钠基压电单晶的籽晶诱导固相生长与构效关系研究

Usually single crystal has an ideal crystalline structure and its propeties are also better than that of ceramics. As a promising lead-free piezoelectric material, potasium sodium niobate is one of candidates which could be able to replace lead-based piezoelectric materials. Recently, a seed-free solid-state crystal growth technology has been developed. However, the continual growth of single crystal by this technology is still difficult. Seed-induced solid-state crystal growth technology is a new ceramic-crystal preparation technique. By this technique, polycrystalline ceramic can be contrally transformed into single crystal below the melting temperature of ceramics by seed-induced process. The best advantage of the solid-state crystal growth is that it can overcome the shortcomings of high-temperature melt growth method. Its cost is also very low compared with the melt growth method. In this project, we will choose potasium sodium niobate system as the research object and prepare big potasium sodium niobate baesd lead-free piezoelectric single crystal by seed-induced solid-state crystal growth technology. Through controlling the composition, different additions and sintering aids, the size, quality and electric properties of single crystals will be designed and controlled. The research results will provide experimental and theoretical foundation for the future applications.

单晶具有一种理想的晶体结构，通常压电单晶的压电性能远远超过陶瓷材料。铌酸钾钠体系作为一种极具潜力的无铅压电材料，是未来替代铅基压电材料从而实现环境保护功能的优先选项之一。最近，铌酸钾钠单晶的无籽固相晶体生长技术被成功发展起来，但是晶体的继续长大目前仍在不小的问题。籽晶诱导固相晶体生长技术是一种新型的陶瓷—晶体制备技术，陶瓷晶粒通过单晶籽晶的诱导，能够在陶瓷原料熔点以下，可控固态再结晶生长，实现多晶陶瓷向单晶材料的转变。固相晶体生长最大的优势在于能够克服高温熔体法生长单晶的缺点，和高温熔体法相比成本也非常低廉。因此，本项目选择以铌酸钾钠基无铅压电材料为研究体系，采用籽晶诱导固相晶体生长技术制备出大的铌酸钾钠基无铅压电单晶，通过控制材料组分、不同离子掺杂和助烧剂种类，设计和调控铌酸钾钠单晶的生长尺寸、晶体质量以及电学性能，为其实际应用提供实验和理论基础。

铌酸钾钠（KNN）压电陶瓷已经成为了一种可以替代含铅压电陶瓷（PZT 陶瓷）的重要选择。本项目对于 KNN 陶瓷的合成、掺杂、改性和 KNN 单晶制备进行了比较系统的研究，为固相烧结法制备KNN单晶提供了进一步基础。通过掺入微量的Bi、Li和Ta，通过固相烧结法可制备分子式为0.96K0.45Na0.55 Bi0.004Nb0.996O3 -0.04LiTaO3的单晶，尺寸可达到4mm*3mm*1.5mm，掺入的Bi、Li和Ta可以完全固溶形成稳定的钙钛矿结构，室温为正交相，准同晶型区间接近室温，获得最好的压电性能，压电常数达到d33=178pC/N。将稀土Ho和Tm掺入到锂掺杂KNN中制备0.94K0.45Na0.55NbO3-0.06LiNbO3：0.005Ho/Tm陶瓷，Ho和Tm的掺入使钙钛矿结构将由原先的四方相转换成了正交相，实现细化晶粒，提 升了相转变温度To-t，降低了居里温度Tc，压电常数达到d33=151pC/N。