Single crystal growth, structure refinement, ferroelastic domains and phase transitions of the hausmannite CuCr₂O₄

Abstract

With a view to studying the optical, structural and magnetoelectric properties, single crystals of the hausmannite CuCr₂O₄ have been grown by a high temperature solution method, based on the thermal decomposition of K₂Cr₂O₇ in the presence of CuO. X-ray powder refinements at room temperature indicate that the crystal structure of CuCr₂O₇ can be accurately described by the centrosymmetric space group I4₁/amd. Crystal cuts have been examined by means of polarized light microscopy in reflection, revealing ferroelastic domain structures consistent with the tetragonal symmetry. The phase transitions in the copper chromite have been studied both by in situ optical domain observations and by DTA and DSC measurements. The ferroelastic phase transition from the tetragonal to the cubic phase has been found to take place at 853 K and to be of first order. The magnetic phase transition has been revealed by a DSC peak at 157 K with a small enthalpy of 0.2 J/g.

Key Words:

• Copper chromite
• single crystal growth
• crystal structure
• ferroelastic domains
• structural and magnetic phase transition.