The oxidative transformation of solid, barium-metal-bearing precursors into monolithic celsian with a retention of shape, dimensions, and relative density

Abstract

The conversion of Ba–Al2O3 –Si–SiO2, Ba–Al–Al2O3 –SiO2, and Ba–Sr–Al–Al2O3 –SiO2 precursors into monolithic, monoclinic celsian has been examined. The relative amounts of metal and oxide in each type of precursor were adjusted so that the overall stoichiometry and molar volume were similar to those of the desired product, celsian. Metal + oxide mixtures were mechanically alloyed and then uniaxially pressed to yield 84–92% dense precursor disks. The precursors were converted into celsian by exposure to a series of heat treatments from 300–1500 °C in oxygen-bearing gases. Differences and similarities in the phase evolution of the various precursors are discussed. Celsian disks were produced that retained the precursor shape, dimensions, and relative (% theoretical) density.