Abstract In this work, Zn2SnO4:Co2+ (0.1%) was obtained through a solid-state reaction at high temperature using ZnO, SnO2, and CoCO3. The sample was investigated using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and photoluminescence spectroscopy. Rietveld refinements of the X-ray diffraction data showed two crystalline phases, Zn2SnO4 and SnO2, with proportions of 97.24% and 2.76%, respectively, while Zn and Sn atoms were observed by X-ray fluorescence. Scanning electron microscopy images showed the polycrystalline nature of the material. Photoluminescence spectroscopy showed two emission bands in the red and near-infrared regions, with the broader and more intense band having a barycenter at 694 nm. The intensity of the emission changed with the excitation wavelength, whereas the barycenter remained unchanged. The intensity, shape, and position of the bands, as well as the calculated crystal field parameters, indicate the insertion of Co2+ ions in the tetrahedral sites of the Zn2SnO4 material.

This work presents the investigation, at room temperature, of Zn2TiO4samples containing Ni2+ ions as substitutional impurities. Samples with molecular formula Zn2(1-x)Ni2xTiO4, 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 Zn2(1-x)Ni2xTiO4 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 Zn2(1-x)Ni2xTiO4was obtained from photoacoustic absorption spectra.

O objetivo deste trabalho foi a investigação das propriedades ópticas da amostra LiGaSiO4 contendo Fe3+ como impureza substitucional. Materiais do tipo óxido dopados com metais de transição podem apresentar bandas largas de absorção e emissão nas regiões do visível e do infravermelho próximo. Estas bandas são sintonizáveis e permitem um amplo número de aplicações em medicina, comunicações e lasers de estado sólido, por exemplo. As amostras dopadas com 5% de Fe3+ foram produzidas por métodos cerâmicos a partir dos óxidos ultrapuros Li2CO3, beta-Ga2O3, SiO2 e Fe2O3, na forma de pastilhas de 10 mm x 2 mm. O tratamento térmico foi realizado a 1000ºC por 96 h em forno com pressão ambiente. Após a síntese, as amostras foram pulverizadas e examinadas por difração de raios X em um difratômetro de pó e os dados obtidos foram comparados com a base JCPDS. Verificamos a formação do LiGaSiO4 acompanhado pelas fases espúrias LiGa5O8 e gama-Li5GaSi2O8. A seguir foram realizadas as espectroscopias fototérmica e de fotoluminescência à temperatura ambiente. Os espectros obtidos exibem largas bandas de absorção e de fotoluminescência. A partir dos dados ópticos identificamos os níveis de energia envolvidos nas transições, obtivemos o tempo de vida das transições radiativas, calculamos os parâmetros de campo cristalino e de repulsão intereletrônica e identificamos a simetria dos sítios de ocupação do Fe3+ na amostra.

The proposal of this work was the investigation of optical properties of LiGaSiO4 samples using Fe3+ ions as substitucional impurity. Oxide materials doped with transition metals can present broad absorption and emission bands in visible and near infrared regions. These bands are tunable and allow various applications, in medicine, communications and solid state lasers, for example. The samples containing 5 at % of Fe3+ were produced by ceramic methods from high purity raw oxides Li2CO3, beta-Ga2O3, SiO2 and an appropriated amount of Fe2O3 and pressed in circular tablets with 10 x 2mm. The thermal treatment duration was 96 h under a temperature of 1000ºC in ambient pressure electric furnace. After the thermal treatment, samples were pulverized and examined by X ray diffraction in a powder diffractometer, and the obtained data compared with JCPDS data base. We verify the formation of LiGaSiO4 accompanied by LiGa5O8 and gamma-Li5GaSi2O8 undesirable phases. In sequence we carried out the room temperature photothermal and photoluminescence spectroscopy. The obtained spectra show wide photoluminescence and absorption bands. From the optical data we identified energy levels and radiative lifetimes, calculated the crystal field and electronic repulsion parameters and identified the site symmetry of the Fe3+ in the samples.