The study of thermal expansion properties in solid solutions Ln 2− xCr xMo 3O 12 (Ln=Ho and Lu) by high temperature X-ray diffraction

Abstract

A systematic study of the formation, crystal structures and thermal expansion properties of solid solutions Ln 2− x Cr x Mo 3O 12 (Ln=Ho and Lu) has been performed. Rietveld refinement results indicate that compounds Ho 2− x Cr x Mo 3O 12 with 0≤ x≤0.2 and Lu 2− x Cr x Mo 3O 12 with 0≤ x≤0.5 have orthorhombic structures and show negative thermal expansion in the temperature range of 200–800 °C. Compounds Ln 2− x Cr x Mo 3O 12 with 1.7≤ x≤2.0 have monoclinic structures and show strong positive thermal expansion in the temperature range of 25–300 °C. While compounds Ln 2− x Cr x Mo 3O 12 with 1.7≤ x≤2.0 adopt orthorhombic structures and show very low positive thermal expansion from 500 to 800 °C. Though the crystal structure plays the key rule in determining the thermal expansion properties, chemical composition and temperature also show important effect on the thermal expansion properties of these compounds.