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

Abstract

and a ¼ 14.0713(2),, respectively. Their crystal structures can be described as a framework of CaO 6 octahedra and V 2 O 7 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 ¼ 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 ¼ 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.

Self‐Activated Vanadate Compounds Toward Realization of Rare‐Earth‐Free Full‐Color Phosphors

“…It is known that some vanadates and oxofluorovanadates exhibit self‐activated photoluminescence (PL) without a foreign luminescent center. Several types of vanadate compounds have been reported so far and are still intensely interested as being revisited very recently (Table ). The commonly recognized features for the vanadate phosphors are as follows: VO 4 or VOF 4 clusters in the crystal structures work as the luminescent centers.…”

“…The excitation is spin allowed, whereas the emission is spin forbidden, which brings relatively long decay time in the order of milliseconds for the vanadate phosphors . On the other hand, the origin of the luminescence itself is ambiguous yet, although Zubkov et al . suggested a role of O − defects in the V–O polyhedra. The PL color varies from blue with YVO 4 to red with KVOF 4 through green and yellow, where the VO 4 tetrahedra or VOF 4 polyhedra work as the luminescent centers in the compounds without any foreign luminescent center.…”

Electrical properties and complex impedance analysis of K2ZnV2O7

“…Vanadium oxides based materials have attracted much attention due to their fascinating structures, electronic, optical and magnetic properties, which are relevant to such diverse areas as lubrication, chemical sensor, catalysis, cathode materials in batteries, electrochromic devices and minerals [1][2][3][4][5].…”

Improved Synthesis of Alkali Metal Vanadates Using a Hydrothermal Method

“…The melilite-type, A2 + B 2+ C2O7 (A = alkali metal; B = divalent metal or similar charge, and C = pyrogroups), layered vanadate structures are of interest for luminescence applications [10,11]. They are related to the fresnoite-type structure except that the B 2+ dication site forms distorted tetrahedra as compared to the square pyramids of the fresnoite-type structure.…”

“…There are two related space groups, P-421m and P42/mnm, in which all B 2+ C2O7 layers have the same vanadium polyhedra orientations and the A + monocations lie between the layers in square antiprismatic coordination environment, but the two B 2+ C2O7 layer types are related by mirror planes and two crystallographically independent A + form a distorted square prism, respectively. If the B 2+ dication site is an alkaline earth metal, the compounds crystallize in the monoclinic space group P21/n with BO6 octahedra sharing corners with pyrovanadates forming 2-D sheets of hexagonal motifs [10].…”