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Phosphor materials with narrow emission bands and high quantum efficiency have received a good amount of attention, suggesting the possibility of several applications in the field of optoelectronic devices. SrTiO 3 :Pr is an example of a material with these characteristics. In this study, mesocrystal samples of Sr 0.998 Pr 0.002 Ti 1−y Al y O 3 (SrTiO 3 :Pr,Al) were prepared via a hydrothermal route, and the morphology presented a microcube shape and pristine structure with Pm3m space group without any spurious phases for all Al concentrations. Measurements of X-ray absorption spectroscopy (XAS) at Ti K-, L II , III -, and O K-edges, calculated projected density of states, and Raman spectroscopy revealed that the hydrothermal method and Al incorporation cause a local symmetry breaking, deviating from the cubic structure, Ti off-center displacement, tilting of TiO 6 octahedra, and O vacancies. As the Al content increases, the intensity of some emissions in the photoluminescence spectra also increases up to 3 at%. The disorder produced by Al concentration leads to a lower symmetry around Pr3+ sites, resulting in an increase in the probabilities of transitions for Pr3+ ions due to the mixing of the opposite parity in 4 f configurational levels. On the other hand, higher Al concentrations cause a decrease in the intensity of Pr emissions, which is related to their quenching because of O vacancies. Additionally, intrinsic defects due to the hydrothermal route and Al incorporation generate a broad emission in the photoluminescence spectra. This broad emission is associated with intermediary electronic levels in the band gap caused by these intrinsic defects. • Sr 0.998 Pr 0.002 Ti 1−y Al y O 3 phosphor mesocrystals were prepared via hydrothermal route. • The morphology presents microcube shape of the mesocrystals without spurious phases. • X-ray absorption spectroscopy detected local disorder and O vacancies. • Lower symmetry around Pr3+ increases the probabilities of the 4f transitions. • Intrinsic defects generate a broad emission in photoluminescence spectra. [ABSTRACT FROM AUTHOR]

Abstract Pr3+-doped perovskite-based SrTiO 3 phosphors have been developed as a potential red phosphor. In this paper, we report the substitution of La3+ ions for Sr2+ ions in order to promote Sr vacancies to further enhance photoluminescence. Given that the La content increases, an enhancement in the intensity of all emissions is observed, mainly for 1D 2 –3H 4 and 3P 0 –3H 6 transitions. This enhancement of photoluminescence emissions is associated with disorder in the lattice caused by La incorporation. Raman measurements and X-ray absorption near edge structure (XANES) spectra at the Ti K-edge identify this disorder as a function of the La content. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Zinc sulfide (ZnS) is a II–VI inorganic semiconductor material and has received remarkable attention because of fundamental physical properties, versatility, nontoxicity, chemical stability and has been widely applied to make numerous optical devices as phosphor material. As a wide band gap semiconductor, ZnS can easily host different metal ions as luminescent center to improve or modify its structural and optical performances such as Cu atoms. In this paper, ZnS:Cu nanoparticles were synthesized by solvothermal method and the photoluminescence and the structural at long- and local-range properties were characterized. According to X-ray diffraction results, ZnS sample crystallizes with the cubic zinc blende structure (F- 43 m space group) without spurious phases. Images from transmission electron microscope depict the morphology of ZnS particles as round shape and average size value lower than 5 nm. Theoretical and experimental X-ray absorption near edge structure (XANES) spectra at Zn K-edge suggest the incorporation of Cu atoms into the ZnS host and indicate the occurrence of Zn and S vacancies, which are confirmed by extended X-ray absorption fine structure (EXAFS) fit results. These native defects are related to a red-shift observed in the peak emission of photoluminescence (PL) spectrum for ZnS sample, which is centered at ~ 504 nm. An emission in orange-red region is observed as Cu is incorporated in the ZnS host matrix that is attributed to the transition from the 4T 1 level to the 6A 1 level. Moreover, the intensity of the emissions due to zinc vacancies and interstitial zinc in the deconvoluted PL spectrum is in accordance with results determined in X-ray absorption spectroscopy characterization. [ABSTRACT FROM AUTHOR]