Effects of yttria content and sintering temperature on the microstructure and tendency to brittle fracture of yttria-stabilized zirconia

Abstract

Purpose: The purpose of this work is to evaluate the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria, based on a study of changes in the microstructure, phase composition, and fracture micromechanisms. Design/methodology/approach: The series of 3YSZ, 4YSZ, and 5YSZ ceramic specimens were sintered in an argon atmosphere. Three sintering temperatures were used for each series: 1450°C, 1500°C, and 1550°C. Microhardness measurements were performed on a NOVOTEST TC-MKB1 microhardness tester. The configuration of the imprints and cracks formed was studied on an optical microscope Neophot-21. The fracture toughness of the material was estimated using both the Vickers indentation method and a single-edge notch beam (SENB) test performed under three-point bending at 20°C in air. The microstructure and morphology of the fracture surface of the specimens were studied using a scanning electron microscope Carl Zeiss EVO-40XVP. The chemical composition was determined using an INCA ENERGY 350 spectrometer. Findings: Peculiarities of changes in the microstructure, the morphology of specimens fracture surface, and mechanical characteristics of YSZ ceramic materials of different chemical and phase compositions sintered in a temperature range of 1450°C to 1550°C are found. Research limitations/implications: To study the actual behaviour of YSZ ceramic materials under operating conditions, it is necessary to evaluate their Young’s moduli, strength, microhardness, and fracture toughness in an operating environment of the corresponding parameters (temperature, pressure, etc.).Practical implications: Based on the developed approach to estimating the propensity to brittle fracture of the formed YSZ ceramic microstructure, it is possible to obtain YSZ ceramic material that will provide the necessary physical and mechanical properties of a wide variety of precision ceramic products. Originality/value: An approach to estimating the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria is proposed based on two methods of evaluating crack growth resistance of materials, namely, the Vickers indentation method and SENB method.