Influence of water on the structure of anion deficient perovskite BaSr2TaO5.5

Abstract

In the present work, a new method for creating oxygen vacancies in the perovskites structure was investigated. The methods studied were based on solid state reactions but used different slurry medium, namely acetone and water. The purpose of the solvents is to enhance the homogeneity of the mixtures, and to create dry and wet media for the initial reaction. The main aim of the study is to investigate the impact of an aqueous slurry medium on the structural characteristics of the BaSr2TaO5.5 perovskite. The oxide was characterized by scanning electron microscopy, thermogravimetric analysis, and X-ray and neutron diffraction. The compound was prepared and has a face centered cubic structure with space group Fm̅m. The two synthetic methods produce monophasic powders and these differ in color, particle size, and hardness. The cell edges of the oxides obtained by mixing the reactants with water are larger than these obtained when the mixing was conducted with acetone. The neutron diffraction profiles demonstrate that A cation and oxygen ions are disordered in the structure. The unusual thermal expansion of the unit cell is due to the presences of water and anion deficiency into the oxides structures.