High-temperature structural phase transition in multiferroic LiCu_2O_2

TL;DR

This study investigates the high-temperature phase transition in LiCu_2O_2, revealing a reversible first-order transition from orthorhombic to tetragonal structure around 993 K, linked to cation order-disorder processes.

Contribution

The paper provides the first detailed analysis of the high-temperature structural phase transition in LiCu_2O_2 using multiple experimental techniques.

Findings

Reversible first-order phase transition at 993 K

Observation of peaks in DTA and jumps in unit cell parameters

Transition related to order-disorder of Cu2+ and Li+ cations

Abstract

LiCu_2O_2 single crystals were studied in the temperature range 300-1100 K by means of heating-cooling curves of differential thermal analysis (DTA), thermogravimetry (TG), X-ray powder diffraction and electrical measurements. A reversible first-order phase transition between orthorhombic and tetragonal phases was found to take place at 993 K. At the transition, a peak is observed in the DTA curves, as well as jumps of the unit cell parameters and electrical resistivity. Considering the crystal structure of LiCu_2O_2 and the entropy change associated with the phase transition, it is concluded that the phase transition is related to processes of order-disorder of the Cu2+ and Li+ cations onto their crystallographic positions.