4F-2 Effects of Increasing Environmental Temperature on the Practical Performance of PMN-PT and PZN-PT Single Crystals

It has been demonstrated previously that lead magnesium niobate-lead titanate (PMN-PT) and lead zirconate niobate-lead titanate (PZN-PT) single crystals can provide higher transducer bandwidth and sensitivity than commercially available zirconate titanate (PZT) ceramics. However, a significant concern with these new materials is the existence of a phase transition, TRT, at a relatively low temperature, which may degrade the materials' piezoelectric performance in practical use for underwater sonar applications. This paper reports the effects of temperature on PMN-PT and PZN-PT single crystal in comparison to conventional piezoceramics, focusing on the changes observed in the materials' electrical impedance magnitude spectra, |Z|, which in turn permit calculation of the materials' thickness mode coupling coefficient, kt, and acoustic velocity, vs. The results show that the piezoelectric performance of the commercial standard, PZT ceramic, remains constant over the observed temperature range. In contrast the piezoelectric properties of PMN-PT single crystal degrade significantly, with relatively rapid variations with temperature above 75degC. PZN-PT shows less variation below 90degC but its properties degrade very rapidly above this temperature. However, the properties of both materials are still acceptable up to a working limit of at least 60degC.