The reactivity of CaTi4(PO4)6 (CTP) with alumina and yttria-stabilized zirconia (Y-TZP)
ceramics was studied. CTP powder was synthesized and composites with commercial alumina or
zirconia matrices containing 10 wt% of CTP were prepared. They were sintered at different
temperatures and characterized using XRD, SEM, and EDX analyses. The results showed that the
alumina/CTP and Y-TZP/CTP composites start to react below 1000 °C. In the alumina/CTP
composite the first reaction product, detected at 970 °C, was AlPO4. At temperatures above 1280 °C
TiO2 and CaTiO3 were also formed and no CTP peaks could be detected using XRD analysis. The
composite sintered at 1500 °C consisted of Al2O3 matrix, AlPO4, TiO2, CaTiO3 and Al2TiO5. The
reaction products formed in the Y-TZP/CTP composite at 970 °C were TiO2 and Ca2Zr7O16. At
higher sintering temperatures, 1280 °C and above, CTP was no longer present, Ca2Zr7O16
decomposed, forming CaO2 and ZrO2, and Y2O3 was consumed to form YPO4. Consequently, upon
cooling to room temperature the matrix phase transformed to monoclinic ZrO2. Based on these
results it can be concluded that CTP is not a suitable bioactive second phase for the fabrication of
CTP composites with alumina or zirconia matrices.
d0 Ferromagnetism in Ag-doped monoclinic ZrO2 compounds
