Effect of heating rate on electromechanical properties of PNN–PZT solid solution

Lead nickel niobate–lead zirconate titanate (Pb(Ni_1/3Nb_2/3)_0.5–Pb(Zr_0.15Ti_0.35O₃), (PNN-PZT)) solid solution was synthesised by columbite process. Samples sintered at various heating rates for 4 h holding and their effect on electromechanical properties have been studied. When heating rate was 8°C/min from room temperature to 900°C and holding for 4 h at 1280°C, highest relative permittivity and piezoelectric charge constant were observed, whereas heating rate of 3.5° C/min and holding for 4 h at 1280°C have shown inferior electromechanical properties and grain coarsening. The piezoelectric charge constant (d₃₃) ~612 pC/N and dielectric constant (e)~ 5950 observed in fast heating rate specimen as against to d₃₃~ 137 pC/N and e~4294. XRD result shows the formation of pyrochlore-free perovskite phase. Fine grains were observed for fast heating rate specimens.