Study of the effect of synthetic procedure on microstructure, defects and magnetism of multiferroic CuFeO 2 ceramics

In this work, the multiferroic material CuFeO2 (CFO) ceramic is fabricated by solid-state reaction with different synthetic procedure. The effects of synthetic procedure on microstructure, evolution of defects and magnetic properties of CFO ceramic are studied in detail. The phase structure and morphology of CFO ceramic that depend on the synthetic procedure are indicated by X-ray diffraction and scanning electron microscopy results, respectively. X-ray photoelectron spectroscopy measurements show the impure Cu2+ ions are present in all CFO samples. Positron annihilation technique is applied for detection of defects and electron density of positron traps. The results reveal that the vacancy defects are present in all samples and the average size of defects and geometry of volume defects increases significantly with the increasing sintering temperature, while the concentration and distribution of electron density of positron traps remains the same. The typical results are that the lifetime τ2 increases from 0.399 to 0.559 ns and the density I2 decrease from 25.1 to 8.2% for samples sintered at 950 and 1100 °C, respectively. Magnetic measurements display that the stability of antiferromagnetic phase is inhibited by sintering temperature but not affected by sintering time. The research shows that the stability of antiferromagnetic phase is mostly related with lattice structure, element valence state and the evolution of vacancy defects within samples under different synthetic procedure.