NANOSTRUCTURED ZIRCONIA COMPOSITES STABILIZED WITH CeO 2 FOR BIOMEDICAL APPLICATIONS C. ENOIU 1 , A. VOLCEANOV 2 , E. VOLCEANOV 2 , R. GAVRILA 1 1 National Institute for Microtechnologies IMT-Bucharest, E-mails: claudiae@imt.ro ; ralucag@imt.ro 2 Faculty of Industrial Chemistry, University “Politehnica” of Bucharest, E-mails: avolceanov@oxy.pub.ro Received May 28, 2004 The paper presents the influence of additives on the stabilization of ZrO 2 powders, with the main objective of obtaining ceramics-ceramics composites with improved thermo-mechanical and biocompatibility properties. Comparative analyses were made on zirconia powders in the ternary system ZrO 2 -CeO 2 -SrO. Investigations of microstructure and surface morphology were performed using scanning electron microscopy and atomic force microscopy. Key words: composite materials, zirconia, stabilising oxides, biomaterials, biocompatibility. 1. INTRODUCTION The researchers became very interested in zirconia based ceramics in the last decades, due to the wide range of applications of these oxide materials and their exceptional properties: electrical, mechanical and thermal properties – ionic conductors (oxygen sensors, heating elements), structural and refractory ceramics (component of thermal motors, gas turbines); biocompatibility properties – bioinert ceramics used in medicine. Zirconia as a pure oxide does not occur in nature but it is found in baddeleyite and zircon (ZrSiO 4 ), which form the main sources for the material. Zirconia has three polymorphic forms, corresponding to crystalline structures with cubic, tetragonal and monoclinic symmetry. The polymorphic transitions can be represented as follows: 2680 C 2370 C 1170 C 950 C liquid (melt) cubic tetragonal monoclinic ⎯⎯⎯⎯→ ⎯⎯⎯⎯→ ⎯⎯⎯⎯→ ←⎯⎯⎯⎯ ←⎯⎯⎯⎯ ←⎯⎯⎯⎯ The transformation of monoclinic to cubic zirconia is accompanied by a large change in lattice size, determined by the volume shrinkage. Due to the rapid phase change and the effects of contraction at heating and expansion at Rom. Journ. Phys., Vol. 49, Nos. 9– 1 0 , P. 777–787, Bucharest, 2004