Artigo sobre y-tzp

Ceramics International 27 (2001) 705–711 www.elsevier.com/locate/ceramint

Environmental degradation of CuO-doped Y-TZP ceramics
S. Ramesha,*, C. Gillb a Department of Mechanical Engineering, COE, University Tenaga Nasional, Km-7 Jalan Kajang-Puchong, 43009 Kajang, Selangor, Malaysia b University of Sunderland, Chester Road, Sunderland, SR1 3SD, UK Received 2 January 2001; received in revised form 20 January 2001; accepted 1 February 2001

Abstract The phase stabilities of plain and CuO-doped (up to 0.2 wt.%) coated 2.5 mol% Y-TZP ceramics, sintered at 1300 C, were investigated by exposure in hostile environments for periods of up to 2000 h. CuO additions significantly reduced the rate of tetragonal to monoclinic phase transformation compared with that for undoped samples. In addition the mechanical properties of the doped materials were better in all cases. Specimen sectioning, however, revealed that after 200 h even the samples with CuO had developed thin, measurable monoclinic layers. Doping of Y-TZP ceramics with small amounts of CuO is one method of reducing ageing degradation without sacrificing other properties. # 2001 Elsevier Science Ltd and Techna S.r.l. All rights reserved.
Keywords: Environmental degradation; CuO-doped; Y-TZP ceramics

1. Introduction Zirconia-based materials are increasingly being considered in engineering applications as alternatives to other ceramic materials due to their relatively high fracture toughnesses and bending strengths. Values of fracture toughness of greater than 12 MPa m1/2 and tensile strengths of 1000–1500 MPa have been observed for 2.5 mol% yttria-stabilised zirconia [1,2] as compared with alumina [3] which exhibited a low fracture toughness (< 5 MPa m1/2) and a low bending strength (< 600 MPa). In addition the atomic defects (i.e. oxygen vacancies) created in zirconia due to doping with lower-valent cations such as yttrium in order to stabilise the high temperature polymorphs allow the migration of oxygen