  BaZrO3 is by far the most inert crucible material that has been used for melt
processing of high quality single crystal YBCO superconductors. To overcome the
processing difficulties of existing solid-state methods, solution processing
methods are increasingly important in powder synthesis. This study investigates
several methods of producing oxalate precursors for subsequent thermal
decomposition to BaZrO3 with a view to producing high quality BaZrO3 ceramics.
The most favourable system used barium acetate, ammonium oxalate and zirconium
oxychloride, which unlike other previously reported oxalate processes allowed
near stoichiometric precipitation without requiring a large excess of Ba
reagents, elevated precipitation temperatures or slow addition of reagents.
Precise control over precipitate stoichiometry was achieved by variation of the
solution Ba:[Zr+Hf] mole ratio without requiring accurate control over oxalate
addition. XRF, XRD, N2 BET adsorption, DTA/TGA and TEM analysis showed this
process to be capable of producing BaZrO3 powders suitable for ceramics
applications. The phase purity, particle size and surface areas of BaZrO3
powders produced by calcination of these precursors can be adjusted by
variation of stoichiometry and calcination temperature. Crucibles formed from
oxalate precursors have been able to contain Y2O3-BaCuO2-CuO melts for up to
seven days.
