Production and characterization of ZrO 2 ceramics and composites to be used for hip prosthesis Melis Arin Æ Gultekin Goller Æ Jef Vleugels Æ Kim Vanmeensel Received: 6 April 2007 / Accepted: 27 November 2007 / Published online: 25 December 2007 Ó Springer Science+Business Media, LLC 2007 Abstract Tetragonal ZrO 2 polycrystalline (TZP) ceram- ics with varying yttria and ceria content (2–3 mol%) and distribution (coated or co-precipitated), and varying second phase content Al 2 O 3 were prepared and investigated by means of microstructural analysis, mechanical properties, and hydrothermal stability, and ZrO 2 -based composites with 35–60 vol% of electrical conductive TiN particles were developed. The effects of stabilizer content and means of addition, powder preparation, sintering condi- tions, and grain size have been systematically investigated. Fully dense Y-TZP ceramics, stabilized with 2–3 mol% Y 2 O 3 , 2 wt% Al 2 O 3 can be achieved by hot pressing at 1,450 °C for 1 h. The hydrothermal stability increased with increasing overall yttria content. The jet-milled TiN pow- der was used to investigate the ZrO 2 –TiN composites as function of the TiN content. The experimental work revealed that fully dense ZrO 2 –TiN composites, stabilized with 1.75 mol% Y 2 O 3 , 0.75 wt% Al 2 O 3 , and a jet-milled TiN content ranging from 35 to 60 vol% could be achieved by hot pressing at 1,550 °C for 1 h. Transformation toughening was found as the primary toughening mecha- nism. The decreasing hardness and strength could be attributed to an increasing TiN grain size with increasing TiN content, whereas the decreasing toughness might be due to the decreasing contribution of transformation toughening from the tetragonal to monoclinic ZrO 2 phase transformation. The E modulus increases linearly with increasing TiN content, whereas the hydrothermal stability increases with addition of TiN content. Introduction Zirconia can be used for orthopedic implants because of its chemical inertness and for refractory application because of its thermal shock resistance and abrasion resistance [1, 2]. Tetragonal zirconia-stabilized ceramics are candi- date materials for surgical implants. The most important requirement of a biomaterial must be the tissue of the body and the material existing without any inappropriate effect on each other and remaining there for a period of time like for long-term application prosthesis, until the end of life time [3]. A major drawback of zirconia ceramics is their strength reduction, due to an unfavourable tetragonal to monoclinic martensitic phase transformation, with time when they are in contact with physiological fluids. The t ? m transform is a reversible martensitic transformation, associated with a large temperature hysteresis (around 200 °C), a finite amount of volume change (4–5%) and a large shear strain (14–15%), which leads to crumbling of the sintered part made of pure zirconia during cooling [4]. It has been found that zirconia shows transformation toughening mechanism that exhibits resistance to crack propagation and the transformation toughening is influ- enced by the grain size, the grain size distribution and the stabilizer content [5]. The tetragonal phase in zirconia ceramics can be obtained by using yttrium or cerium oxide stabilizers. Yttria is the most popular stabilizer used for zirconia ceramics for its excellent mechanical properties, wear M. Arin Á G. Goller (&) Metallurgical and Materials Engineering Department, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey e-mail: goller@itu.edu.tr J. Vleugels Á K. Vanmeensel Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, Leuven 3001, Belgium 123 J Mater Sci (2008) 43:1599–1611 DOI 10.1007/s10853-007-2343-x