This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional theory(DFT).The calculated results reveal that due to the electron doping,the Fermi level shifts into conduction bands(CBs) for Sr2 Nb x Ti1 x O4 with x=0.125 and the system shows n-type degenerate semiconductor features.Sr2TiO4 exhibits optical anisotropy in its main crystal axes,and the c-axis shows the most suitable crystal growth direction for obtaining a wide transparent region.The optical transmittance is higher than 90% in the visible range for Sr2 Nb 0.125Ti0.875O4.
The SrTiO3∶Pr3+ material,co-doped with monovalent Li+,divalent Mg2+,and trivalent Al3+ was prepared by a new sol-gel method. The phase and crystallinity of the synthesized materials were investigated by powder X-ray diffraction(XRD) and scanning electron microcopy(SEM). Among the co-doped ion,Al3+ incorporation caused the least lattice change and had the best crystallinity. Photoluminescence spectra were taken to investigate the luminescence characteristics. We observed a red luminescence change of SrTiO3∶Pr3+ after being co-doped,and a best enhancement on the red luminescence with the trivalent Al3+ was observed. The present results indicated that the charge defect associated with Al3+ has led to charge compensation of Pr+Sr and also implied that the charge defects(usually the second dopant ions replacing the A or B sites in the lattice) which are closer to Pr+Sr contribute more to the red luminescence enhancement.
