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 (PL ZT) 9/65/35 dagger ceramics prepared with 10 wt% excess PbO were monit ored by quenching uniaxially pressed pellets after a variety of heat t reatments, TEM revealed a PbO-rich amorphous film covering the particl e 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 ap proximately Pb0.87Zr0.15Ti0.04O1.19. The liquid composition moves towa rd the PbO-TiO2 eutectic as sintering progresses. After 10 to 30 min a t 1180 degrees C, the liquid composition was approximately Pb0.9Zr0.04 Ti0.06O1.1 and crystallized on quenching. High densities of dislocatio ns 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. M echanisms for the formation of these dislocations are suggested.