Heat capacity and X-ray scattering studies on phase transitions of Rb₂MoO₄

Abstract

The structural phase transitions of Rb2MoO4 have been reinvestigated using heat capacity measurement and X-ray scattering technique. In as-grown single crystals of Rb2MoO4, the crystal structure is a monoclinic one isomorphous to -K2MoO4 (-sequence) at room temperature. The -sequence transforms into the -sequence (isomorohius to -K2SO4, space group Pnam) at a temperature range from 400 to 500 K. This  transition is reconstructive and depends on both temperature and time, especially with accompanying the temperaturedependent incubation time. In the -sequence, an incommensurate phase characterized by wave vector qx = 1/3 ~ 2/5 was observed below T3=223 K.