Low-Temperature Liquid-Phase Sintering of Zirconia: Phase Composition and Microstructure
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ICAL TECHNOLOGY
Low-Temperature Liquid-Phase Sintering of Zirconia: Phase Composition and Microstructure V. V. Smirnova†, S. V. Smirnova, T. O. Obolkinaa, O. S. Antonovaa, M. A. Goldberga,*, and Corresponding Member of the RAS S. M. Barinova Received December 24, 2019; revised August 21, 2020; accepted September 3, 2020
Abstract—The sintering conditions, microstructure, and phase composition of zirconia-based ceramics containing an additive of 0.2 wt % alumina have been studied. It has been shown that the introduction of sodium disilicate as a low-melting additive promotes a decrease in the sintering temperature of zirconia ceramics to 1080‒1180°C. The materials obtained were characterized by a high content of the tetragonal phase and a finecrystalline structure with a grain size from 40‒50 to 80‒100 nm. It has been shown that the use of sodium disilicate based additives promotes liquid-phase sintering and formation of the dense structure at 1080°C. Keywords: ceramic materials, zirconia, alumina, sodium disilicate, sintering DOI: 10.1134/S0012500820100043
Tetragonal zirconia, which is produced in the form of a solid solution containing 3 mol % Y2O3, is characterized by the highest mechanical properties in comparison with other ZrO2-based materials [1]. Due to its high strength, crack resistance, and wear resistance, as well as chemical inertness and the absence of toxic reactions, such ceramics is used as a material for manufacturing hip and dental implants [2, 3]. At the same time, the high production cost of ZrO2 materials limits their widespread use in biomedicine, mechanical engineering, and other fields of application. One of the ways to reduce the cost of production is the transition from expensive high-temperature sintering and hot pressing to fabricating sintered ceramics at a lower temperature, as well as to additive manufacturing technologies, which ensure a reduction in the technological cycle and the volume of waste in production. The introduction of Al2O3-based additives can decrease the sintering temperature, including for products obtained by additive manufacturing methods, digital light processing [4]. Materials containing from 1 to 16 wt % Al2O3 have been fabricated [5]. It has been found that sintered materials can be obtained at a low Al2O3 content (up to 5 wt %) at 1500–1550°C. It is also possible to intensify the sintering process by introducing additives that
form a melt and cause liquid-phase sintering. Sodium silicate Na2SiO3 (5 wt %) with a melting point of about 1072°C was used as an additive [6]. As a result, dense materials (open porosity less than 1%) were obtained at 1250–1330°С. It was noted that materials containing 1 wt % Al2O3 had the lowest porosity and the highest density, and an increase in the alumina content to 5 wt % led to an increase in open porosity up to 8–10% for materials sintered at 1250°C. At the same time, a further decrease in the sintering temperature should make it possible to use such an additive manufacturing technique as selective laser sintering, which requi
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