Photoluminescence, photoacoustic and structural characteristics of polycrystalline Zn₂TiO-4:Ni²⁺ semiconductor

This work presents the investigation, at room temperature, of Zn₂TiO₄ samples containing Ni²⁺ ions as substitutional impurities. Samples with molecular formula Zn_2(1-x)Ni_2xTiO₄, where x = 0.00, 0.0007, 0.001, 0.0013, 0.002 and 0.003, in which Zn²⁺ ions were replaced by Ni²⁺ ions, were prepared through solid-state method, crystalline data were obtained by X-ray diffraction, the elemental composition was determined by X-ray fluorescence and the optical properties were investigated through photoluminescence and photoacoustic techniques. The photoluminescence spectra showed broadbands from 640 nm to 800 nm. The emission of the Zn_2(1-x)Ni_2xTiO₄ samples was assigned to the overlapping of the Ni²⁺ and the Zn₂TiO₄ emission. The most intense photoluminescence signal was obtained with excitation radiation at a wavelength of 360 nm for the sample with x = 0.001. The photoacoustic spectra showed absorption bands characteristic of semiconductor materials due to the host Zn₂TiO₄. The energy bandgap of the Zn_2(1-x)Ni_2xTiO₄ was obtained from photoacoustic absorption spectra. (author)