Effect of net PbO content on mechanical and electromechanical properties of lead zirconate titanate ceramics

The effect of net PbO content (obtained by taking into account the amount of excess PbO added and PbO loss during sintering) on the mechanical and piezoelectric properties of lead zirconate titanate (PZT) ceramics has been studied. The samples were prepared by the solid state route using the morphotropic phase boundary composition Pb(Zr0.535δTi0.465)O3. Excess PbO was also added to the samples in varying amounts from 0–1.0 wt.%. To vary PbO volatility the samples were sintered with and without a PbO rich atmosphere at 1220°C for 2 h. The resulting Pb content as given by x in Pb1+x(Zr0.535Ti0.465)O3+x varied from x=−1.7×10−2 to 1.8×10−2. The sintered density was found to increase with increasing lead content. The precipitation of the second phase believed to be ZrO2 is observed for x=−1.7×10−2. The fracture mode changed from intergranular to transgranular with increasing x. The fracture toughness (KIC) and strength are minimum near x=0 and increase with increasing as well as decreasing x. The maximum values of KIC and strength are 1.45 MPa m1/2 and 90 MPa, respectively, for x=1.8×10−2. The dielectric constant and piezoelectric strain coefficient d33 increased with x.