THE OXIDATIVE TRANSFORMATION OF SOLID, BARIUM-METAL-BEARING PRECURSORS INTO MONOLITHIC CELSIAN WITH A RETENTION OF SHAPE, DIMENSIONS, AND RELATIVE DENSITY

The conversion of Ba-Al2O3-Si-SiO2, Ba-Al-Al2O3-SiO2, and Ba-Sr-Al-Al2 O3-SiO2 precursors into monolithic, monoclinic celsian has been examin ed. 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 mixtur es were mechanically alloyed and then uniaxially pressed to yield 84-9 2% dense precursor disks. The precursors were converted into celsian b y exposure to a series of heat treatments from 300-1500 degrees C in o xygen-bearing gases. Differences and similarities in the phase evoluti on of the various precursors are discussed. Celsian disks were produce d that retained the precursor shape, dimensions, and relative (% theor etical) density.