Liquid-phase sintering of PZT ceramics

Lead zirconate titanate (abbreviated as PZT) ceramics are of considerable commercial importance for a host of piezoelectric and pyroelectric applications. Conventionally, many PZT ceramics are sintered at temperatures above 1250 degrees C. Such extreme temperatures are undesirable due to the increased energy consumption, limitation of electrode material and evaporation of volatile components. A liquid-phase sintering aid incorporating Cu2O and PbO is presented which demonstrates a reduction in the required sintering temperature of these ceramics. This new aid is described with particular reference to a commercial PZT, termed Pz26, used industrially for its optimised piezoelectric properties. Pz26 has a composition near the morphotropic phase boundary and possesses a tetragonal crystalline structure. Typically this material is sintered between 1260 and 1300 degrees C for 1 h to achieve the required densification. With the inclusion of sintering aid, sintered densities comparable to those obtained by conventional sintering are achieved at only 800 degrees C. The optimum weight percentage of sintering aid varies for different ceramic materials, particle sizes, morphology and the desired sintering temperature. However, with standard "mixed-oxide" produced Pz26 powder and with a median particle size in the range 1.6-1.7 mu m, a value of 5 wt.% allows sintering at 800 degrees C, according to densification, dielectric and piezoelectric measurements (epsilon = 873, tan delta = 1.13 %, k(p) = 43.1%). When finer grained powder is used (d(0.5) = 1.1 mu m), improved properties (epsilon = 960, tan delta = 1.04%, k(p) = 51.7%) are obtained for an addition of 3 wt.% sintering aid and a sintering temperature of 850 degrees C. (C) 2000 Elsevier Science Ltd. All rights reserved.