Pressureless sintering of fluorapatite under oxygen atmosphere

Fluorapatite (Fap) is prepared by precipitation method and sintering in the temperature range 640-1365 degrees C. Linear shrinkage starts at about 715 degrees C and the material reaches its final density at 890 degrees C. Abo ve this value, grain growth becomes important and induces an intragranular porosity which is responsible for density decrease. At 1180 degrees C, a li quid phase is formed as a result of the formation of a binary eutectic betw een Fap and fluorite contained in the powder as impurity. This liquid phase further promotes the coarsening process and induces formation of large por es at high temperatures. (C) 2000 Elsevier Science Ltd. All rights reserved .