Effect of grain size on the phase structure and electrical properties of PZT-PNZN quaternary systems

The quaternary systems 0.74Pb(Zr0.47Ti0.53)O3-0.26Pb[(Ni0.6Zn0.4)1/3Nb2/3]O3(PZT-PNZN) have been prepared using the conventional oxide mixing method in a wide temperature region between 1050 and 1250 °C. All specimens present high relative density above 95%, indicating a wide sintering window for this system. Investigation of the microstructure reveals a continuous increase in grain size from 1.07 to 2.77 μm when the sintering temperature is increased from 1050 to 1250 °C, which obeys the common grain-growth law well. However, unlike compositional component PZN-PZT and PNN-PZT, the phase structure of quaternary PZN-PNZN is not sensitive to the grain size. The specimens with different grain size retain the morphotropic phase boundary (MPB) structure and the size induced phase transition does not appear. Excluding the influence of the phase structure, the size effect plays a dominant role in improving the piezoelectric properties, which facilitates the motion of domain walls due to the decreasing number of grain boundary. The optimum piezoelectric parameters are obtained at 1150 °C: d33 = 307 pC/N, kp = 0.56.