Comparison of MnO2 and ZnO Additives on Zircon Decomposition and Formation of Solid Solution

Abstract

In this paper, the effects of MnO2 and ZnO additives on zircon decomposition were investigated. The substitution of Mn and Zn into zircon lattices and the formation of solid solutions are discussed. The additives were added at 0–4 wt.% to zircon. The phase composition, physical properties, and microstructural changes for the sintered samples were characterized. Results of Rietveld refinement analysis showed that 1 wt.% of both additives retarded the decomposition of zircon. Further addition of additives slightly accelerated the zircon decomposition and improved sample densification. X-ray diffraction peaks of zircon were shifted to higher angles by the addition of MnO2, whereas ZnO did not alter zircon peaks. Energy dispersive spectroscopy analysis detected the presence of Mn and Zn in zircon grains. ZnO has a lower solubility than MnO2 in zircon, leading to the formation of a higher fraction of secondary phases, in turn leading to the suppression of grain growth.