新型压电单晶PMNT的生长、性能及应用

THE GROWTH, PROPERTIES AND APPLICATIONS OF PMNT, A NEW PIEZOCRYSTAL

通过对PMN -PT二元体系在高温下的相结构、相稳定性以及相图的研究 ,确立了PMNT单晶的生长方法 ,用Bridgman方法生长出了大尺寸高质量的PMNT单晶 .目前制备的PMNT单晶尺寸达到40× 70mm ,晶片尺寸为2 0× 2 0× 1mm ,其主要性能为 :介电常数ε～ 5 0 0 0 ,介电损耗tanδ <0 9%,压电系数d3 3 >15 0 0pC N ,机电耦合系数k3 3～ 94%.在准同型相界附近 ,PMNT单晶的压电活性比较高 ,但其结构比较复杂 ,实际应用时应该考虑单晶的综合性能 ,生长组成略为离开相界的PMNT单晶 .在扫描电声显微镜中 ,我们将PMNT单晶用于其压电换能器 ,明显提高了电声像的分辨率 ,充分显示出PMNT在超声成像、水声换能器以及高应变驱动器中有广泛的应用前景 .

A feasible method to grow high-quality large PMNT single crystals by the modified Bridgman technique has been set up on the basis of studies of the phase structure, phase stability and phase diagram of the PMN-PT binary system at high temperature. Single crystals have been grown with a boule size of 40×70mm and plate size of 20×20×1mm 3. The dielectric constant ε is ～5000, loss tan δ<0.9%, piezoelectric constant d 33 >1500pC/N,and coupling k 33 ～94%. The crystals have great piezoelectric activity and unstable properties at a composition near the MPB where the crystal structure is very complex, so growth should take place far from the MPB. The single crystals have been successfully used in transducers for scanning electron acoustic microscopes, with clear improvement in the resolution of the electron acoustic images. These results indicate that PMNT single crystals are promising for applications in medical ultrasonic imaging, sonar transducers and high strain actuators.