K2CaSiO4 or K2O × CaO × SiO2 has been reported to be a major constituent of residual materials that are of interest for the field of applied mineralogy, including ashes from biomass combustion as well as fertilizers produced from the residues of oil‐shale industry or from steelmaking slags. Unfortunately, contradictory results concerning basic crystallographic and physicochemical data of this compound have been described in the literature. In a series of solid‐state reactions we tried to prepare this material for a more detailed investigation. The temperature regime for the subsolidus synthesis experiments was selected according to previous studies where the occurrence of this so‐called “1:1:1” phase had been reported. The samples were characterized by thermal and X‐ray fluorescence analysis as well as X‐ray powder diffraction. Our results indicate that “K2CaSiO4” does not exist as a crystalline phase in the ternary system K2O–CaO–SiO2 and that the 1:1:1 compound, mentioned in earlier studies is actually misinterpreted K2Ca2Si2O7. Furthermore, the start of melt formation of an oxide mixture with composition K2O × CaO × SiO2 has been determined to be 1170°C, which is dramatically lower than the value of 1630°C mentioned in the only available comprehensive but more than 80 years old phase analytical study on potassium calcium silicates.
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Document Type: Research Article
Affiliations: Institute of Mineralogy and Petrography, University of Innsbruck, A-6020 Innsbruck, Austria
Publication date: August 1, 2011