Exploring barium-titanium-peroxo-hydroxide as an excellent single-source precursor for crystallographically diverse barium titanate ceramics - parametric study

Abstract

Barium-titanium-peroxo type amorphous materials gained importance with the advent of wet-chemical methods for the production of crystalline perovskite barium titanate (BaTiO3) electroceramics. In this paper, the chemical nature of the barium-titanium-peroxo precursor was determined by means of elemental (EPMA), spectroscopic (FT-IR and FT-Raman), XRD and thermal (DSC and TGA/DTA) analyses. Several synthesis parameters such as the barium source, the peroxide treatment time, the reaction temperature and the reaction time were investigated. The precursor was also thermally treated at varying temperatures between 30 degrees C and 1000 degrees C. Relatively high reaction temperatures are detrimental to the Ba center dot O center dot Ti structure, resulting in plain TiO2 formation. Though relatively low temperatures (ice bath) are needed to suppress unwanted TiOCl2, ambient synthesis conditions and short reaction time (2 h) resulted in the desired single-source properties, i.e. amorphous Ba center dot O center dot Ti-peroxo structure with Ba/Ti ratio of unity (1.04 +/- 0.04). The addition of an extra stirring step during H2O2 addition lowered the chance of carbonate incorporation in the precursor. Thermal analysis under air and nitrogen atmosphere was performed and a stoichiometric formula of Ba2,08Ti2O(O2)1,9(OH)5,3 center dot 3,1H2O was calculated, which was in very good agreement with literature data. The barium-titanium-peroxo-hydroxide material proved to be an excellent single-source precursor. Phase-pure, highly crystalline and facetted, stoichiometric BaTiO3 particles with differently crystallographically oriented facets were obtained via the molten-salt solid-state method ({100} or {111} oriented facets) as well as the hydrothermal route ({100} oriented facets).