Physical, microstructure enhancement of K0.5Na0.5NbO3- based lead-free ceramics prepared via two-step sintering

Abstract

Electroceramic material of K0.5Na0.5NbO3-based lead-free ceramics has a high potential application to be used as sensors, actuators and transducers. To realize the potential of K0.5Na0.5NbO3, the material must exhibit a high density with homogenous grain size. In this work, the two-step sintering was used to enhance the density and microstructure of the K0.5Na0.5NbO3 (KNN) ceramic to produce better densification. The microstructure of the upper surface and cross section of the KNN pellet as a function of the different sintering conditions are systematically studied using Field Emission Scanning Electron Microscopy (FESEM). The calcined powder was pressed into a pellet using a hydraulic hand press with a pressure of 0.3 tons for 1 min. The KNN pellet then was sent to sinter through conventional sintering and two-step sintering. In the two-step sintering, the first step was sintered at 1120 °C for 10 minutes of soaking time and the second step was sintered at 1070 °C for 10 hours of soaking time. The surface of the sintered specimens under investigation is well polished and thermally etched below the sintering temperature. Evident from the microstructure reveals a highly dense spherical, cubic and rounded shape of grains were received better compactness for samples sintered via two-step sintering compared with conventional sintering that has a large pore between the grain. The sample sintered through two-step sintering showed the highest density (4.244536 g/cm3) compared to the sample sintered through conventional sintering (4.117893 g/cm3).