Tunable broadband emission by bandgap engineering in (Ba,Sr)2(Mg,Zn) WO6 inorganic double-perovskites

Four tungstate double-perovskite materials with a general formula A(2)BWO(6) , where A=Ba, Sr and B]Mg, Zn were synthesized by co-precipitation method. All samples exhibit blue emission under UV excitation resulting from the additional electron states within the material's band gap created by two types of centers: the regular and the inversion tungstate groups. The latter one is defined as a W6+ ion residing at the octahedral B site (B = Mg, Zn). The relative position of those two centers' energy levels to the valence and conduction bands can be altered by the substitution to the A site (Ba/Sr) as well as the B site (Mg/Zn). Substitution of Sr for Ba results in a blue-shift of both excitation and emission spectrum. The substitution of Zn for Mg, in contrast, results in the opposite phenomenon. The substitutions, aside from shifting the emission wavelength of the centers, regulate the ratio between regular and inversion tungstate groups by restricting or allowing the energy transfer between them and influence their thermal stability. The luminescence properties are in agreement with the DFT calculations. The ability to influence their host emission wavelength, intensity, and thermal stability can be crucial in the design of novel luminescent thermometers. (C) 2021 Elsevier B.V. All rights reserved.