Formation of Ba2Ti9O20 ceramics from EDTA-gel-derived powders

Reactive powders have been prepared by the ethylenediaminetetraacetic acid-gel (EDTA) method. Single-phase Ba2Ti9O20 and approximate to98% dense ceramic are readily obtained by sintering the fine powders at 1275 degreesC for 3 h. Powder derived from EDTA-gel precursor results in Ba2Ti9O20 and BaTi4O9 mixed phases when sintering was performed below 1200degreesC, and only become single Ba2Ti9O20 phase above 1250degreesC. However, single-phase Ba2Ti9O20 were obtained at 1150degreesC if ball-milling process was applied to this powder. This is considered to be due to the deagglomeration and improved mixing effects of ball-milling. One batch, the EDTA-gel precursor with ethylene glycol, showing improved decomposition behavior, results in single Ba2Ti9O20 phase at 1200 degreesC. It was observed that the surface areas of derived powders are in the order of precursors from EDTA-ball-milled (13M) > EDTA-ethylene glycol (EG) > EDTA. The formation of single Ba2Ti9O20 phase is enhanced by the high surface area. The microwave properties of Ba2Ti9O20 ceramics obtained from three EDTA-derived powders are discussed and compared. (C) 2002 Published by Elsevier Science B.V.