Phase transition and optical characteristics of Mg doped CuAlO<inf>2</inf> synthesized by facile thermal decomposition process

Abstract

Phase formation, phase composition and structure analysis are essential in understanding the properties of the mixture. This work presents the phase formation and transition of delafossite CuAlO2 with Mg incorporation (0–10 mol%), prepared by a thermal decomposition synthesis. Due to various operating temperatures and dopant concentrations, the X-ray diffraction (XRD) analysis exhibited a phase difference, observed as CuAlO2, CuAl2O4 and CuO. Pristine CuAlO2 preparation was achieved at a firing of 1200 °C for 6 h. Crystallite size and micro-strain of obtained products were approximated by Williamson-Hall and size-strain plot method. Morphology transformation was examined by scanning electron microscope (SEM), showing a surface roughness change depending on the phase composition. Fourier transform infrared spectroscopy (FT-IR) detected Cu-O and Al-O bonding vibration spectral bands, confirming CuAlO2 formation. The energy bandgap (Eg) was found in the range 3.87–3.98 eV as Mg adding 0–10 mol%. The effect of dopant incorporation and phase transition causes the variation of Eg. Photoluminescence spectroscopy (PL) exhibited the near band-edge emission (NBE) at 311 nm (3.99 eV), observing Mg interstitial defect state at 340 nm (3.65 eV) and deep oxygen defect state at 558 nm (2.22 eV). The optical characteristics associating with the dopant and phase component are also discussed.