Synthesis, crystal structure and luminescent properties of pyrovanadates A₂CaV₂O₇ (A = Rb, Cs)

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• 作者：Vladimir G. Zubkov ; Alex ; er P. Tyutyunnik ; Nadezda V. Tarakina ; Ivan F. Berger ; Ludmila L. Surat ; Boris V. Slobodin ; Gunnar Svensson ; Bertil Forslund ; Boris V. Shulgin ; Vladimir A. Pustovarov ; Alexis
• 关键词：Rubidium and cesium vanadium oxide ; Pyrovanadates ; X-ray powder diffraction ; Rietveld refinement ; Crystal structure ; Electron diffraction ; Photoluminescence ; Pulse cathode luminescence
• 刊名：Solid State Sciences
• 出版年：2009
• 出版时间：March 2009
• 年：2009
• 卷：11
• 期：3
• 页码：726-732
• 全文大小：547 K

文摘

The novel vanadium oxides Rb₂CaV₂O₇ and Cs₂CaV₂O₇ have been prepared by solid-state reaction and their crystal structures determined and refined using X-ray, neutron powder and electron diffraction data. Rb₂CaV₂O₇ and Cs₂CaV₂O₇ are isostructural, crystallizing in space group P2₁/n with unit cell parameters: a = 13.8780(1), b = 5.96394(5), c = 10.3376(1) Å, β = 104.960(1)° and a = 14.0713(2), b = 6.0934(1), c = 10.5944(1) Å, β = 104.608(1)°, respectively. Their crystal structures can be described as a framework of CaO₆ octahedra and V₂O₇ pyrogroups with alkaline metals found in the tunnels formed. Photoluminescence (PL) and PL excitation spectra of the considered pyrovanadates have been studied in the vacuum ultraviolet (VUV) to visible light (Vis) range as well as their pulse cathode luminescence (PCL) spectra and the kinetic parameters of PCL. In the PL and the PCL spectra of both pyrovanadates recorded at T = 300 K a broad band with maxima at 2.2, 2.4 eV and two shoulders (bands) at 2.0 and 2.58 eV have been observed. At T = 10 K the band at 2.0 eV becomes the main band in the spectra. Two types of luminescence centers for each pyrovanadate, with very similar excitation bands at 3.75, 4.84, 6.2, 7.3 and 9.1 eV, have been found. The nature of the luminescence centers connected with the bands at 2.0, 2.2, 2.4 and 2.58 eV is discussed.