Sintering of tricalcium phosphate-fluorapatite composites with zirconia

Zirconia (ZrO2) addition effects on densification and microstructure of tricalcium phosphate-26.52 wt% fluorapatite composites were investigated, using X-ray diffraction, scanning electron microscopy and by analysis using 31 P nuclear magnetic resonance. The tricalcium phosphate-26.52 wt% fluorapatite-zirconia composites densification increases versus temperature. At 1300 degrees C, the composites apparent porosity reaches 9% with 5 wt% zirconia. XRD analysis of the composites reveals the presence of tricalcium phosphate, fluorapatite and zirconia without any other structures. Above 1300 degrees C, the densification was hindered by grain growth and the formation of both intragranular porosity and new compounds. The 31 p MAS-NMR analysis of composites sintered at various temperatures or with different percentages of zirconia reveals the presence of tetrahedral P sites. At 1400 degrees C, XRD analysis of the tricalcium phosphate-26.52 wt% fluorapatite-20 wt% zirconia composites shows the presence of calcium zirconate and tetracalcium phosphate. This result indicated that partial decomposition of tricalcium, phosphate during sintering process of composites when 20 wt% or less ZrO2 was added. Thus, zirconia reacts with tricalcium phosphate forming calcium zirconate and tetracalcium phosphate. (c) 2008 Elsevier Ltd. All rights reserved.