Thermal phase transition of potassium sulfate, K2SO4 - A high temperature polarizing light microscopic study

Michihiro Miyake, Ichiro Minato, Shin ichi Iwai

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Abstract

The thermal phase transition of K2SO4 has been investigated by high temperature polarized light microscopy. K2SO4 undergoes a first-order transition at 587° C where the orthorhombic low temperature form (Pmcn) transforms into a hexagonal high temperature modification (P63/mmc). Prior to the beginning of the phase transition, K2SO4 shows an anomalous optical behavior. The crystal apparently becomes optically uniaxial twice at 338° and 425° C, respectively, and truly optically uniaxial at 587° C. The phase transition propagates through an intermediate temperature form, which is sandwiched between the low and the high temperature forms and moves in a definite direction, 〈130〉 (orthorhombic indices), in the vicinity of the phase transition. Passing through the phase transition point on cooling, dark belts crossing each other are observed which are a result of the transformation twins parallel to {110} and {130}.

Original languageEnglish
Pages (from-to)307-315
Number of pages9
JournalPhysics and Chemistry of Minerals
Volume4
Issue number4
DOIs
Publication statusPublished - 1979
Externally publishedYes

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ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Materials Science(all)

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