COMPOSITIONAL EFFECT ON THE LIQUID-PHASE FORMATION IN LEAD IRON TUNGSTATE FERROELECTRIC CERAMICS

The iron content in Pb(Fe2/3W1/3)O3 was demonstrated in this study to substantially affect the formation of a liquid phase during the heating process. This liquid phase was generated in iron-deficient specimens at a temperature around 870-degrees-C. However, no liquid phase could be formed in specimens with a stoichiometric or excess amount of iron. A slow cooling treatment induced the liquid phase to migrate from the interior toward specimen surfaces and formulate a platelike phase. Formation of the liquid phase is attributed to the reaction of Pb2WO5 with residual iron species. The chemical gradient which occurred as a result of the temperature difference between the interior and the surface during slow cooling, as well as the capillary force in the narrowed pore channels between densified grains, are considered to be the driving forces for the migration of the liquid phase.