| Photoluminescence of Phosphors Containing W-O Emission Complexes Aida Tulegenova1; Liudmila Lisitsyna2; 12AL-FARABI KAZAKH NATIONAL UNIVERSITY, Almatу,, Kazakhstan; 2TOMSK STATE UNIVERSITY OF ARCHITECRURE AND BUILDING, Tomsk,, Russian Federation; PAPER: 93/AdvancedMaterials/Regular (Oral) SCHEDULED: 17:10/Sat. 26 Oct. 2019/Leda (99/Mezz. F) ABSTRACT: Natural phosphors like MeWO<sub>4</sub>, possessing high light emissions at small volumes, are considered to be a promising material for X rays and γ-scintillators. Nanostructured MeWO<sub>4</sub> materials are promising candidates for photoluminescence. During the past decade, unique properties of these materials such as photocatalytic activity, photochromism and electrochromism have attracted the attention of researchers. Photoluminescence in ZnWO<sub>4</sub> crystals, WO<sub>3</sub> crystalline micropowders, as well as in LiF crystals and MgF<sub>2</sub> ceramics doped with tungsten trioxide, was researched at 300 K. Prepared As phosphors were not transparent in the range ≥4 eV (WO<sub>3</sub>, ZnWO<sub>4</sub>), or they became opaque in this range after doping with tungsten trioxide (LiF crystals, MgF<sub>2</sub> ceramics). Emission was excited by photons with 6>E<sub>ph</sub> ≥ 4 eV. The focus of these studies is on the emissions of phosphors with different types of matrices. What they have in common is that the lattices contain W-O polyhedrons. The following was revealed: - Spectral-kinetic characteristics of the phosphors' photoluminescence in the visible range (band at 2.6-2.7 eV) are independent of the width of the band gap (from 13 till 3.8 eV), of the lattice structure of phosphorus matrices and of the method of preparing the materials (grown in air, sintering, laser ablation). - The emission characteristics of phosphors: spectral position of emission band, the value of long-lived time decay, the emission band FWHW and the value of the Stokes shift are similar to those in the WO<sub>3</sub> crystalline micropowder. It looks as if emission centers were created under UV irradiation in specific areas of phosphors with the same properties in all materials under research. - The work deals with a hypothesis according to which the presence of the WO<sub>3</sub> phase in phosphor matrices defines the structure of emission centers (oxygen-depleted polyhedron W<sup>6+</sup>nO<sup>2-</sup>) and high sensitivity to UV irradiation. The latter is due to the small width of the band gap of the WO<sub>3</sub> lattice (3.8 eV) compared with those in the researched phosphorus matrix lattices. - The emission in the WO<sub>3</sub> material is of a recombination nature. It means that wide-gap dielectric phosphors doped with WO<sub>3</sub> (LiF and MgF<sub>2</sub>), free electrons, and holes are created when E<sub>ph</sub><E<sub>g</sub> in the matrices. Perhaps, in this case, photocatalytic activity, photochromic, and electrochromic properties are inherent properties of many oxides of transition metals revealed in WO<sub>3</sub>-containing materials [1, 2]. References: [1] J. Grabis, D. Jankovica, M. Kodols, D. Rasmane. Latvian J. Chem., 1/2 (2012) 93-98 [2] G. Huang, Y. Zhu. J. Phys. Chem. C, 111 (2007) 11952-1195 |
