Properties of alumina ceramics obtained by conventional and non-conventional methods for sintering ceramics

Purpose: The aim of this study was to obtain ceramic alumina materials by using the conventional free sintering process, 2.45 GHz microwave sintering (MW) and spark plasma sintering (SPS). Technical and ultra-pure alumina was used to obtain specimens. The effect of temperature and time of sintering on the density, porosity, Young’s modulus and Vickers hardness of Al2O3 ceramics was determined. Mechanical and physical properties of the obtained materials were compared between the methods of sintering. Design/methodology/approach: Al2O3 ceramics materials were sintered by the conventional free-sintering process and the non-conventional methods comprise microwave sintering and spark plasma sintering. Density, porosity, elastic modulus and Vickers hardness were determined for the obtained materials from technical and ultra-pure alumina. Findings: The use of advanced sintering processes allowed the authors to receive alumina ceramic materials with good mechanical and physical properties at the time of one minute for microwave sintering to ten minutes for spark plasma sintering. According to the theory sintering temperature increases with increasing of alumina purity, which was confirmed in the carried out works on the basis of Young’s modulus values and density values. Practical implications: Alumina ceramics made by the microwave sintering process and spark plasma sintering can be applied as the ceramics for cutting tools and also elements of the pharmaceutical equipment because microwave sintering ensures purity of the sintered materials. Originality/value: The non-conventional methods for sintering ceramics primarily comprises (SPS) and (MW). SPS simultaneously applies pulsed electrical current and pressure directly on the sample leading to densification at relatively lower temperatures and short retention times. In the recent years, MW occurred as an advanced sintering technique in the world. Among many works on sintering alumina and alumina-composites until now there have been no reports of microwave sintering of alumina in Poland. Microwave sintering offers increased density and requires lower sintering temperature and time. Shorter sintering prevents the grain growth process, which provides better microstructure and, thanks to these, better mechanical and physical properties. Keywords: Ultra-pure alumina; Microwave sintering; Spark plasma sintering; Free sintering; Mechanical properties.