Effects of calcination temperature on the synthesis of [KNbO3]0.9 – [BaNi0.5Nb0.5O3]0.1 perovskite powders

Abstract

ABSTRACTThe phase and structural properties of [KNbO3]1−x - [BaNi0.5Nb0.5O3]x (KBNNO) perovskite powders with x = 0.1, which have been prepared by using the combustion technique, are reported. The investigated calcination temperatures are between 500°C and 1000°C. The perovskite structure phase is found for all samples. All main peaks in X-ray diffraction (XRD) patterns can be correlated with KNbO3 cubic structure (JCPDS no. 08-0212). Highly pure perovskite crystalline phase is found in the sample calcined at 650°C, which is about 100 – 250°C lower than that of the conventional solid-state reaction technique. However, the impurity phases occur in the samples calcined in temperature range between 700°C and 1000°C. These impurity phases might originate from contamination of atmospheric oxygen or other matters. By continuously varying dwell time, we found a suitable condition for synthesis KBNNO powder, which is the calcination temperature of 650°C and the dwell time of 1.5 h. This result is confirmed by the calculated percent perovskite, XRD peak intensity and width. The crystalline size calculated by using Scherrer's equation, which is around 21 – 24 nm, tends to increase with the increase of calcination temperature and dwell time. Rietveld refinement method is applied to determine the lattice parameters of both tetragonal KNbO3 and hexagonal BaNi0.5Nb0.5O3.