MICROSTRUCTURAL EVOLUTION DURING PRESSURELESS SINTERING OF LEAD LANTHANUM ZIRCONATE-TITANATE CERAMICS WITH EXCESS LEAD(II) OXIDE

The early stages of sintering of lead lanthanum zirconate titanate (PLZT) 9/65/35 dagger ceramics prepared with 10 wt% excess PbO were monitored by quenching uniaxially pressed pellets after a variety of heat treatments, TEM revealed a PbO-rich amorphous film covering the particle surfaces and interparticle porosity in pellets quenched after 5 min at 1125 degrees to 1180 degrees C. This amorphous phase is indicative of the presence of a high-temperature liquid phase with composition approximately Pb0.87Zr0.15Ti0.04O1.19. The liquid composition moves toward the PbO-TiO2 eutectic as sintering progresses. After 10 to 30 min at 1180 degrees C, the liquid composition was approximately Pb0.9Zr0.04Ti0.06O1.1 and crystallized on quenching. High densities of dislocations with (b) over right arrow = 1/2[110] and low-angle boundaries were observed in samples quenched from 1180 degrees C after 10 to 30 min. Mechanisms for the formation of these dislocations are suggested.