ABSTRACT
Sintered polycrystals and single crystals grown by the skull melting technique of ZrO2 with Y2O3 and MgO additions have been studied. The mechanical properties of the materials were investigated over a wide range of temperatures. The stress–strain relationships were measured from –140 to 1400°C, the hardness from 20 to 900°C(at 10N) and the critical stress intensity factor, K1c, at –150 and 20°C. R–curve behaviour, indentation toughness https://www.w3.org/1998/Math/MathML"> K c v https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003421290/07e4de97-c68f-4ca1-95b4-28d8b410031d/content/eq306.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> , and dynamic elastic moduli Ed were determined at room temperature. It was shown that R–curves for crystals with different additives and ceramics with Y2O3 additions were horizontal. At room temperature all these crystals exhibit linear elastic behaviour and those crystals with higher Ed had higher K1c, https://www.w3.org/1998/Math/MathML"> K c v https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003421290/07e4de97-c68f-4ca1-95b4-28d8b410031d/content/eq307.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> and Kr values. The temperature dependence of the ductile to brittle transition was significantly lower for indentation tests than for flexural tests. Results indicate that the partially stabilised crystals exhibited higher strength and greater creep resistance than polycrystalline materials at high temperatures.
