Intrinsic nonstoichiometry in the lead zirconate-lead titanate system determined by Knudsen effusion

The range of the intrinsic nonstoichiometry in lead zirconate‐titanate at 1100 °C has been established independently by two gravimetric techniques. A modified Knudsen effusion experiment allowed for an extended interpretation of the vapor pressure data. A single experiment was used to determine the width of any ${\mathrm{Pb}}_{\text{1−x}}{\square }_x\mathrm{\hspace{0.17em}(}{\mathrm{Ti}}_y{\mathrm{Zr}}_{\text{1−y}}){\mathrm{O}}_{\text{3−x}}{\phi }_x$ single‐phase region, the equilibrium PbO vapor pressure, activity data as a function of both temperature and composition, and the exact location of the stoichiometric composition within the single‐phase region. The ``vapor phase equilibration'' (VPE) method was used as a supplemental measurement of the width of most PZT single‐phase regions. Results obtained by the two methods for the extent of nonstoichiometry were in close agreement (x_max = 0.10 at y = 1.0; x_min = 0.016 at y = 0.40; T = 1100°C). The Knudsen effusion experiment established that for all the compositions studied, the stoichiometric composition, Pb(Ti_yZr_1−y)O₃, was coincident with the (liquid + PZT) phase boundary.