巨压电弛豫铁电单晶及其在医用超声换能器中的应用

压电材料是一类非常重要的多功能材料。它可以实现机械能和电能之间的相互转换,在机电器件和电声领域有广泛的应用。基于宽频带超声波换能器、高灵敏度传感器和大应变执行器等压电器件的发展需求,迫切地需要研发出具有更大压电应变常数和更高机电耦合系数的压电材料。弛豫铁电单晶铌镁酸铅-钛酸铅(化学分子式(1-x)Pb(Mg_(1/3)Nb_(2/3))O_3-xPbTiO_3简称PMN-xPT或PMN-PT)及其同类单晶(简称弛豫铁电单晶)的发现恰逢其时,它们所具有的巨压电性和极高的机电耦合系数使得很多机电器件的性能有了一次大幅度的改进。例如:PMN-33%PT单晶的压电常数d_(33)高达2800 pC/N,是通用的压电材料PZT压电陶瓷的5倍,其机电耦合系数k_(33)也高达94%,而最好的PZT的机电耦合系数k_(33)也只能达到70%。本文系统地介绍了弛豫铁电单晶材料及其在医用超声换能器方面的应用进展。

Relaxor-based ferroelectric single crystals with giant piezoelectric properties and their applications in medical ultrasound transducers

Piezoelectric materials, which have the ability to convert mechanical energy into electrical energy or vice versa, have been widely used in making electromechanical devices and in the field of electro-acoustics. The advancement in broadband ultrasonic transducers, high sensitivity sensors, and large strain actuators need the piezoelectric materials to have larger piezoelectric constants and higher electromechanical coupling factors. A relaxor-based ferroelectric single crystal (1-x)Pb(Mg_1/3Nb_2/3)O_3-xPbTiO₃ (PMN-xPT or PMN-PT) and its modified version (commonly referred as relaxor-based ferroelectric single crystals) fulfilled such demands, which have giant piezoelectric coefficients and very high electromechanical coupling factors. For example, the piezoelectric constant and electromechanical coupling factor of PMN-33%PT are 2 800 pC/N and 94%, respectively. This article intends to provide an overview on the development of relaxor-based ferroelectric single crystals and their applications in medical ultrasound transducers.