Effect of the two-step sintering to the phase structure, microstructure and dielectric properties of undoped K0.5Na0.5NbO3-Based lead-free ceramics

Abstract

The two-step sintering with a low temperature in synthesizing a homogeneous microstructure in Potassium Sodium Niobate (K0.5N0.5Nb3 @ KNN) piezoceramic without not normal grain growth was studied. The KNN ceramics prepared through conventional sintering at temperatures up to 1120 °C resulted in homogeneous microstructures with a bimodal grain size distribution. In contrast, the two-step sintering (1120°C for 10 minutes in the first step and 1070 °C for 10 hours in the second step) resulted in a homogeneous microstructure with a grain size of a few micrometers. The samples prepared by two-step sintering had high dielectric properties comparable to samples prepared through conventional sintering for Lead Zirconate Titanate (PZT). KNN bulk ceramic with homogeneous microstructures was successfully synthesized by a two-step sintering method and their dielectric properties were measured. The key requirements are piezoelectric ceramics with a small grain size, near-full density and the intended stoichiometric one to one ratio to fabricate colossol-performance energy harvesters.