Structural and electrical properties of zirconia/hydroxyapatite porous composites

Zirconia/hydroxyapatite porous composites containing 7.58-32.89% ZrO(2) were sintered at 1000 and 1250 degreesC. Relative porosity (DeltaP) decreases with increased ZrO(2) content at both firing temperatures. Sintering at 1250 degreesC, however, was accompanied by higher DeltaP as a consequence of a partial transformation of HA (hydroxyapatite) to beta-TCP (beta-tricalcium phosphate) besides partial stabilization of the ZrO(2) tetragonal phase. The higher ZrO(2) 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 beta-TCP denoting cell contraction with higher ZrO(2) content and sintering at 1250 degreesC. Scanning electron microscopy (SEM) showed the presence of HA and ZrO(2) in the composite sintered at 1000 degreesC. The transformation of monoclinic ZrO(2) to the tetragonal phase and HA to beta-TCP at 1250 degreesC was assured. The dielectric constant epsilon' and loss epsilon" values were minimum at low measuring temperatures (298-593 K) and low frequencies (frequency range 10(2)-1 x 10(6) HZ). Multiple relaxation peaks and frequency shifts in conductivity/frequency relations were related to zirconia content, elimination of CO(3)(2-) and porosity as well as multiple phase achieved at high sintering temperature. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.