Effect of ZrO 2 addition on crystallization behaviour, porosity and chemical–mechanical properties of a CaO–TiO 2–P 2O 5 microporous glass ceramic

Abstract

2–6 mol% ZrO 2 was added to a base glass composition of P 2O 5 31.25, CaO 43.75, TiO 2 25 (mol%) at the expense of TiO 2. The prepared glasses were crystallized to bulk glass ceramics containing the major phases of β-Ca 3(PO 4) 2 and CaTi 4(PO 4) 6. DTA was utilized to determine the appropriate phase separation–nucleation and crystallization temperatures. The crystalline products and resulting microstructures were examined by XRD and SEM. The β-Ca 3(PO 4) 2 phase was dissolved out by leaching the resulting glass ceramics in HCl, leaving a porous skeleton of CaTi 4(PO 4) 6. It was shown that ZrO 2 addition resulted in reduction of volume porosity and mean pore diameter while the specific surface area was increased. The smallest median pore diameter and largest surface area were 8.6 nm and 32 m 2 g −1 respectively obtained for the specimen containing 6 mol% ZrO 2. The ZrO 2 addition also improved the chemical durability and bending strength of porous glass ceramics.