Synthesis and structural relationship of complex tantalum phosphates in the flux system K₂O-P₂O₅-Ta₂O₅-MoO₃

Single crystals of K2Ta4O11 (I), K(TaO2)2PO4 (II) and K3Ta 5O11(PO4)2 (III) were synthesized by flux-aided method in the pseudo-quaternary system K2O-P 2O5-Ta2O5-MoO3. Tight interrelation of their crystal structures has been found via X-ray diffraction study. Experimental solid-state band gap measurements revealed its semiconductor nature corroborated with DFT calculations. Local structure of PO4 groups in (II) and (III) compounds was probed with 31P MAS NMR spectroscopy. © 2012 IEEE

Possibility of Application of ZrP2O7ZrP_2O_7 and KZr2(PO4)3KZr_2(PO_4)_3 Intrinsic Luminescence for Monitoring of γ\gamma-Irradiation

Polycrystalline powders of ZrP2O7 and KZr2(PO4)3 phosphates reveal photoluminescence (PL) emission bands in near ultraviolet (UV) (250–330 nm), short-wavelength visible (350–550 nm) and the long-wavelength visible (450–700 nm), spectral regions under excitations with vacuum ultraviolet (VUV) synchrotron (90–330 nm), UV (337'nm) and visible (473 and 532 nm) laser radiation respectively. Emission in the longer-wavelength region (650–1000 nm) is observed for KZr2(PO4)3 crystal under VUV synchrotron excitation. Both ZrP2O7 and KZr2(PO4)3 crystals reveal substantial changes in the luminescence spectra under irradiation with γ-rays from 60Co source. Possibility of application of the luminescence method for monitoring ionizing radiation dose absorbed by ZrP2O7 and KZr2(PO4)3 crystals is examined. Optimal experimental conditions of the method are estimated. The origin of PL emission bands is discussed

Luminescence spectroscopy and electronic structure of ZrP2P_2O7O_7 and KZr2Zr_2(PO4O_4)3)_3 crystals

The photoluminescence (PL) of ZrP2O7 and KZr2(PO4)3 phosphate crystalline micro-powders grown by spontaneous crystallization method is studied under vacuum ultra-violet (VUV) synchrotron radiation excitations (4–20 eV region of excitation photon energies) in 8–300 K temperature region. The electronic structures (partial densities of states) and optical absorbance spectra of the crystals are calculated by the Full-Potential Linear Augmented Plane Wave Method. Both phosphate crystals reveal PL emission band in the UV spectral region peaking near 300 and 295 nm for ZrP2O7 and KZr2(PO4)3 respectively. The spectral profile of the band weakly depends on temperature. The excitation spectra of the UV emission in each crystal contain intensive excitation band peaking at 189 and 182 nm for ZrP2O7 and KZr2(PO4)3 respectively. The excitation band of the UV emission is related to band-to-band electronic transitions with charge transfer from O 2p to Zr 4d states. The energy band gaps Eg of ZrP2O7 and KZr2(PO4)3 are estimated as 6.7 and 6.6 eV respectively