Reactive sintering of phosphorous coated BaTiO3

Doping BaTiO3 with P5+ has been reported to decrease the sintering temperature of the ceramic, allowing homogeneous line grained microstructures to be obtained. According to the present paper, the formation of a phosphorous-BaO rich phase covering the BaTiO3 particles seems to be the origin of the improved porosity coalescence and removal observed at the earlier sintering stage of these materials. The formation and development of phosphorous-barium rich phases have been followed by means of DRX, and high temperature NMR. Phosphorous cations incorporated from phosphate estes form a surface layer covering the BaTiO3 particles which reacts during heating to form Ba2TiP2O9 and/or Ba-3(PO4)(2). Formation of these phases seem to occur by solid-solid reaction involving phosphorous diffusion through the BaTiO3 particles. (C) 1999 Elsevier Science Limited. All rights reserved.