Visible PL Phenomenon at Room Temperature in Disordered Structure of SrWO4 Powder

Abstract

The SrWO 4 (SWO) powders were synthesized by the polymeric precursor method and annealed at different temperatures. The SWO structure was obtained by X-ray diffraction and the corresponding photoluminescence (PL) spectra was measured. The PL results reveal that the structural order-disorder degree in the SWO lattice influences in the PL emission intensity. Only the structurally order-disordered samples present broad and intense PL band in the visible range. To understand the origin of this phenomenon, we performed quantum-mechanical calculations with crystalline and order-disordered SWO periodic models. Their electronic structures were analyzed in terms of band structure. The appearance of localized levels in the band gap of the order-disordered structure was evidenced and is a favorable condition for the intense PL to occur.

Synthesis, growth process and photoluminescence properties of SrWO4 powders

“…Therefore, the strong and sharp peaks indicate that the SrWO 4 powders processed in MH are highly crystallized and structurally ordered at long-range. This result shows that the MH system promotes the formation of crystalline SrWO 4 powders with low heat treatment temperature and reduced processing time than the conventional methods [2,5]. The experimental lattice parameters and unit cell volume were calculated using the least square refinement from the UnitCell-97 program [47].…”

“…At room temperature, the tungstates and molybdates present a scheelite-type tetragonal structure with general formula ABO 4 (A = Ba, Ca, Sr, Pb; B = W, Mo) and space group I4 1 /a [1][2][3][4][5]. In this type of structure, the B ions are within tetrahedral O-ion cages and isolated from each other, while the A ions are surrounded by eight oxygens [6,7].…”

Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states

“…The overall result is that the unit cell deforms and the structure is no longer cubic but of reduced symmetry, such as orthorhombic, rhombohedral, tetragonal, monoclinic, and triclinic phases, depending on the details of the [BO6] octahedral rotations and B-site distortions. This influences the electronic and optical properties of materials, behavior of photo-generated charge carriers, including excitation, transfer, and redox reactions, and plays an important role in their technological applications [6,17,[26][27][28][29][30]. It should be realised that the absorption transition of the [BO6] cluster corresponds to an electron transition from a bonding to a nonbonding molecular orbital, i.e.…”