Chemical synthesis of tantalum zirconate from alkoxide precursors

Abstract

A chemical route for low temperature synthesis of tantalum zirconate (Ta 2Zr 6O 17), a potential microwave dielectric material, is reported for the first time. Mixed cation precursor powders, derived using a molecularly modified tantalum ethoxide and zirconium acetylacetonate, were calcined at low temperatures (780 °C) to form single-phase crystalline Ta 2Zr 6O 17. The structural evolution of the crystalline phase was studied using X-ray diffraction, Fourier transform IR spectroscopy, differential thermal analysis and thermogravimetric analysis. The overall weight loss during the conversion of dried powders to crystalline Ta 2Zr 6O 17 was approximately 36%. A 14% weight loss occurring gradually up to 240 °C was due to the removal of occluded solvent and water. Following this, three exothermic events attributed to decomposition of the organic components occurred at 310, 467, and 633 °C. Differential thermal analysis data showed that crystallization of the amorphous precursor occurred at 710°C. Accompanying the crystallization was a consistently observed weight loss of approximately 2%. Analysis of evolved gas suggested that this was mainly due to the pyrolysis of residual carbon. Preliminary results on sinterability indicated that using crystallized and classified submicrometer powders, it was possible to obtain ceramics with dense microstructures (approximately 97% theoretical density) by sintering at 1575 °C for 1 h.