Morphology control of high-quality hexagonal perovskite BaNiO3 by molten salt method

Abstract

BaNiO3 single crystals with a hexagonal perovskite structure are prized for their exceptional Ni oxidation state and face-sharing structure, which grants them a high-performance potential as electrocatalysts. Despite their potential, obtaining high-quality morphology of BaNiO3 single crystals remains a challenge, making their characterization difficult and limiting their efficiency. In this study, we present a method for synthesizing high-quality BaNiO3 single crystals by morphology control using a molten salt method, which involves modifying the concentration of KOH, reaction time, and cooling rate. The optimal conditions for synthesizing high-quality BaNiO3 single crystals were found to be a reactant-to-KOH ratio of 1:50 and a reaction time of more than 3 h, which resulted in hexagonal-prism-shaped single crystals. However, using different reactant-to-salt ratios and shorter reaction times led to the formation of polycrystalline or pine-needle-shaped BaNiO3 along with secondary phases of BaCO3 and NiO. A higher KOH concentration required a longer reaction time, as the precursor diffusion rate slowed down. The average size of BaNiO3 single crystals increased as the cooling rate decreased, reaching the average width of similar to 90 mm and the length of over 1 mm at the cooling rate of 5 degrees C/h. Our findings present optimal conditions for synthesizing a high-quality single-crystalline BaNiO3 with a hexagonal perovskite structure and could contribute to the development of BaNiO3 crystals for applications in ferroelectrics, photovoltaics, and chemical catalysis. (c) 2023 Elsevier Ltd. All rights reserved.