PMN-PT单晶与陶瓷在性能及相变方面的特点

着重介绍了用Ｂridgman方法生长的（１-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-PT)固溶体单昌在介电，压电、热释电性能及相应方面的一些特点；①异常高的电常数d33(高达３０００pC/N以上），耦合系数kg(在０．６以上），k33(达０．９０），高的介电常数ε（高达５００甚至更高），低的Ｑm值（约６０），热释电系数也较高。②强烈的各向异性。③随着ＰＴ含量的增加，系统的弛豫行为逐渐减弱，在x=0．３３时，材料在室温下成为正常铁电体，但ＰＥ－ＦＥ相变并非正常铁电相变，表现在Ｔ＞Ｔm时，ε－Ｔ关系不遵守居里－包斯定律，而是遵守Ｓmolenskii的关系。该相变也明显地与弥散相变不同，这种行为可用无场的观点加以解释。

Characters of Piezoelectricity and Phase Transition of PMN-PT Single Crystals and Ceramics

Some special features in dielectric, piezoelectric properties and phase transition behavior of (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 (PMN-PT) (x=0.24, 0.3, 0.33 and 0.35) single crystals grown by Bridgman method were outlined: 1) Extremely high piezoelectric constant d33 (up to 3000 PC/N) and coupling factors k33 and kt (up to 0.94 and 0.62 respectively), low mechanical factor of merit (Qm~60), large dielectric constant (~5000).2) Strong orientation dependence of piezoelectric properties. 3) with increasing PT content, the system becomes less relaxational, but at least upto x=0.35, the system still partly exhibites relaxor feature: for x=0.33 and 0.35. ~ T curves look sharp enough to show a normal ferroelectric like feature, however when T> Tm the ~ T relation does not obey Curie-Weiss law, but follows Smolenskii's relation. The piezoelectric properties of PMN-PT ceramics are similar to PZT-5H, but with higher e and k31.