The structure of the high-temperature form of CaSeO4, formed by dehydration of the gyspum-type structure dihydrate is presented. The material is equivalent to that described previously as a P21212 1 form, but is however, a monazite with unit cell a = 6.85661(16) Å, b = 7.04962(15) Å, c = 6.68817(15) Å and β = 104.2675(21)° in space group P121/n1. Also presented is evidence for two intermediate trigonal and pseudo-trigonal phases related to the structurally similar minerals rhabdophane, bassanite, and γ-CaSO 4. This result permits closer comparisons between intermediate-temperature structures of the selenate with related sulphates, and orthophosphates with a view to extending structural stability via synthesis of solid-solutions.
Monazite structure from dehydrated CaSeO4.2H2O / W. Crichton, H. Mueller, M. Merlini, T. Roth, C. Detlefs. - In: MINERALOGICAL MAGAZINE. - ISSN 0026-461X. - 74:1(2010), pp. 127-139.
Monazite structure from dehydrated CaSeO4.2H2O
M. Merlini;
2010
Abstract
The structure of the high-temperature form of CaSeO4, formed by dehydration of the gyspum-type structure dihydrate is presented. The material is equivalent to that described previously as a P21212 1 form, but is however, a monazite with unit cell a = 6.85661(16) Å, b = 7.04962(15) Å, c = 6.68817(15) Å and β = 104.2675(21)° in space group P121/n1. Also presented is evidence for two intermediate trigonal and pseudo-trigonal phases related to the structurally similar minerals rhabdophane, bassanite, and γ-CaSO 4. This result permits closer comparisons between intermediate-temperature structures of the selenate with related sulphates, and orthophosphates with a view to extending structural stability via synthesis of solid-solutions.
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