Mono-phase bio-ceramics (alumina and zirconia) are widely used as femoral heads in total hip replacements (THR) as an alternative to metal devices. Unfortunately, the orthopaedic community reports significant in-vivo failures. Material scientists are already familiar with composites like alumina-zirconia. Since both are biocompatible, this could prove to be a new approach to implants. This paper deals with a new generation of alumina-zirconia nano-composites having a high resistance to crack propagation, and as a consequence may offer the option to improve lifetime and reliability of ceramic joint prostheses. The reliability of the above mentioned three bio-ceramics (alumina, zirconia and zirconia toughened alumina) for THR components is analysed based on the study of their slow crack-growth behaviour. The influence of the processing conditions on the microstructure development, of the zirconia toughened alumina composites and the effect of these microstructures, on its mechanical properties, are discussed. r

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The transformation β→α in Mg‐substituted Ca3(PO4)2 was studied. The results obtained showed that, contrary to common belief, there is, in the system Mg3(PO4)2–Ca3(PO4)2, a binary phase field where β+α‐Ca3(PO4)2 solid solutions coexist. This binary field lies between the single‐phase fields of β‐ and α‐Ca3(PO4)2 solid solution in the Ca3(PO4)2‐rich zone of the mentioned system. In the light of the results and the Palatnik–Landau's Contact Rule of Phase Regions, a corrected phase equilibrium diagram has been proposed. The practical implications of these findings with regard to the synthesis of pure α‐ and β‐ Mg‐substituted Ca3(PO4)2 powders and to the sintering of related bioceramics with improved mechanical properties are pointed out.