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 ≈98% dense ceramic are readily obtained by sintering the fine powders at 1275 °C for 3 h. Powder derived from EDTA–gel precursor results in Ba2Ti9O20 and BaTi4O9 mixed phases when sintering was performed below 1200 °C, and only become single Ba2Ti9O20 phase above 1250 °C. However, single-phase Ba2Ti9O20 were obtained at 1150 °C 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 °C. It was observed that the surface areas of derived powders are in the order of precursors from EDTA-ball-milled (BM)>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.