Temperature-dependent Raman scattering and photoluminescence in YBa2Cu3O7 doped with SiO2 and Zn0.95Mn0.05O nanoparticles: comparative study

Abstract

A combined study examining the temperature dependencies of Raman scattering and photoluminescence (PL) of a YBa2Cu3O7 (YBCO) matrix doped with SiO2 (12 nm; 0.01 wt%, 0.10 wt%) and Zn0.95Mn0.05O (20 nm; 0.02 wt%, 0.10 wt%) nanoparticles was presented. X-ray diffraction (XRD) analysis confirms that both YBCO types exhibit a perovskite structure with the orthorhombic Pmmm phase. The microstructure was examined using environmental scanning electron microscopy (ESEM). Raman scattering and photoluminescence measurements as functions of temperature were conducted in the 77–837 K range. The photoluminescence intensity is observed to decrease for the doped YBCO than for the pure YBCO, because of localized defects. The photoluminescence spectrum is primarily composed of three bands at 1.60, 1.88, and 2.40 eV. A clearly pronounced correlation is observed between electronic and structural changes in the doped YBCO, which is due to the temperature, illumination, added oxygen or metal ions, and spectral parameters. The PL integrated intensity as a function of the inverse temperature was simulated using the Arrhenius model. This analysis reveals that the energy exchange between the different levels in the pure and doped YBCO was conducted via two vibration modes only, which are strongly linked to the oxygen and copper atoms in the YBCO matrix. The temperature dependencies of the modes at 340 and 500 cm−1 exhibit softening with temperature increase, resulting from microstructure control, which may be due to small concentrations of Si, Zn, and Mn substitutions at the chain Cu(1) and plane Cu(2) sites.