Zirconia has broad application prospects in the industry, but unlike metal materials, it is difficult to control the microstructure and improve mechanical properties of ceramics through post heat treatment. This article proposes a plasma treatment technique at room temperature and studies the effects of plasma treatment and applying current on the microstructure of ceramics, achieving grain size control of dense 3YSZ (3mol% yttria stabilized zirconia) ceramics. The results indicate that plasma treatment can promote the grain size of 3YSZ ceramics from submicron (0.45 μm) to tens of microns (>90 μm) in a short period of time. Applying current has a promoting effect on the rapid grain growth of ceramics. When the current is 1.0 A, the maximum grain size of zirconia can reach 255 μm, which is approximately 565 times larger than the initial grain size. The rapid grain growth caused by this plasma treatment can be attributed to the enrichment of oxygen vacancies induced by the electric field and the influence of plasma action on the rapid migration of grain boundaries. Compared with traditional heat treatment, plasma treatment technology has the advantages of high efficiency and low energy consumption, providing new ideas for ceramic microstructure control and single crystal material preparation.

Aluminum oxide (Al₂O₃), as a high-performance structural ceramic material with high melting point, high toughness, good chemical stability, and excellent wear resistance, is one of the best candidate materials for high-temperature wear resistant components. It has been widely used in aerospace materials, military industry, and biomedical fields. However, most ceramic materials do not have lubrication functions, especially under dry friction and high temperature conditions, where the friction coefficient and wear rate are relatively high. Therefore, the main strategy for preparing ceramic lubricating composite materials is to introduce single or complex solid lubricating components into the ceramic matrix, in order to form a lubricating film or transfer film during the friction process to achieve anti friction and anti-wear effects. Meanwhile, the inherent brittleness and high wear performance of Al₂O₃ ceramic materials greatly limit their applications in related fields. Therefore, how to improve the mechanical properties of Al₂O₃ ceramics is crucial for their application. In order to clarify the influence of different lubricating phases on the composition, microstructure, and mechanical properties of Al₂O₃ ceramics, three different lubricants, graphite, Mo, and LaF₃, were selected to be added to the Al₂O₃ ceramic lubricating material matrix. A series of Al₂O₃ ceramic lubricating materials were prepared by hot pressing sintering method. Then, the properties of the material were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), BET, and three-point bending methods, and the influence of lubricant type and content on the microstructure and mechanical properties of Al₂O₃ was analyzed. The results indicate that the type and content of lubricants have a significant impact on the microstructure and mechanical properties of the material. As the content of non-metallic lubricating phases increases, the hardness, bending strength, and fracture toughness of the composite material decrease significantly. Adding Mo can significantly improve the strength and toughness of composite materials, mainly because Mo not only makes Al₂O₃ denser, but also plays a role in ductile phase toughening.