Structural and electrical properties of zirconia/hydroxyapatite porous composites

Zirconia/hydroxyapatite porous composites containing 7.58–32.89% ZrO2 were sintered at 1000 and 1250 °C. Relative porosity (ΔP) decreases with increased ZrO2 content at both firing temperatures. Sintering at 1250 °C, however, was accompanied by higher ΔP as a consequence of a partial transformation of HA (hydroxyapatite) to β-TCP (β-tricalcium phosphate) besides partial stabilization of the ZrO2 tetragonal phase. The higher ZrO2 content and/or sintering temperature resulted in reduced a-axis of HA and increased its c-axis. On the other hand, a reduction of both a- and c-axes is recorded in the formed β-TCP denoting cell contraction with higher ZrO2 content and sintering at 1250 °C. Scanning electron microscopy (SEM) showed the presence of HA and ZrO2 in the composite sintered at 1000 °C. The transformation of monoclinic ZrO2 to the tetragonal phase and HA to β-TCP at 1250 °C was assured. The dielectric constant ε′ and loss ε″ values were minimum at low measuring temperatures (298–593 K) and low frequencies (frequency range 102–1×106 HZ). Multiple relaxation peaks and frequency shifts in conductivity/ frequency relations were related to zirconia content, elimination of CO32− and porosity as well as multiple phase achieved at high sintering temperature.