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Abstract: A series of rare-earth zirconate RE2Zr2O7 nanocrystals (RE=La, Nd, Eu and Y) were prepared by a simple combustion method. These compounds possess either a pyrochlore structure (P-RE2Zr2O7) or a defect fluorite structure (F-RE2Zr2O7), which depends on the ionic radius of RE3+. The photoluminescence (PL) property of the as-prepared RE2Zr2O7 nanocrystals was studied, and the observed emissions in the UV and visible range were attributed to different transition mechanisms for RE2Zr2O7 with different RE ion. A PL mechanism has been proposed, associated with the transition between the valence band and a mid-gap state related to oxygen vacancies. Divalent Pb ions were introduced into RE2Zr2O7 nanocrystals and the luminescence of the Pb2+-doped samples was also recorded for comparison. The PL property of RE2Zr2O7 was found to be intimately related to their intrinsic defect structure, and PL was thought as a new method to estimate the degree of disorder in the A2B2O7 structure (from pyrochlore structure to defect fluorite structure). [Copyright &y& Elsevier]

Abstract: Highly luminescent euxenite phased YNbTiO6:Eu3+ and Li+-doped YNbTiO6:Eu3+ red phosphors have been prepared through a facile sol–gel combustion process and investigated for the first time. The introduction of Li+ ions into YNbTiO6:Eu3+ is able to result in significant changes of the crystallinity and particle size, and bring a clear red-shift of absorption edge. A dominant red emission peak at 611nm due to the 5D0 → 7F2 transition of Eu3+ was observed from photoluminescence spectra of the YNbTiO6:Eu3+ and Li+-doped YNbTiO6:Eu3+ phosphors. In particular, the emission intensity of the optimal Li+-doped YNbTiO6:Eu3+ was examined to be close to 400% of commercial Y2O3:Eu3+ phosphor. The mechanism of the enhanced emission by Li+ doping was discussed. [Copyright &y& Elsevier]

Abstract: Three-dimensional reticular-structured luminescence SrAl2O4:Eu,Dy powders were prepared by refluxing- and sonication-combustion synthesis without using any surfactant for the first time and were characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy. All the samples have a very porous, open and spongelike morphology with fractal properties. The excitation and emission spectra of the products have been measured by Edinburgh FLS920 at room temperature. The new formation-mechanism of the three-dimensional reticular-structure was proposed in this article. [Copyright &y& Elsevier]