Effects of chemical substitution on the structural and optical properties of α-Ag2−2xNixWO4 (0 ≤ x ≤ 0.08) solid solutions

Abstract

In this work, we investigated the effects of chemical substitution on the structural, electronic, and optical properties of α-Ag_2−2xNi_xWO₄ (0 ≤ x ≤ 0.08) solid solutions prepared by a facile microwave-assisted hydrothermal method. The results showed that the increase of Ni concentration in α-Ag₂WO₄ microcrystals as a host matrix caused a morphological transformation and a shift of the electronic and optical properties. Based on first principles calculations and using Wulff's construction, particle shapes and their transformations in α-Ag₂WO₄ and α-Ag_2−2xNi_xWO₄ can be affected by controlling the ratios of surface energy values between the different facets. In addition, theoretical calculations revealed that Ni substitution in α-Ag₂WO₄ is more favorable in the Ag₂ and Ag₄ positions, in which the local coordination of Ag atoms corresponds to clusters with coordination numbers of seven and four, respectively. This behavior could be related to the degree of medium-range structural disorder in α-Ag_2−2xNi_xWO₄ crystals. The experimental results were correlated with theoretical simulations to achieve a deeper understanding of the relationship between morphology and properties. These results provide the basis for a rational design for the compositional modulation of structural and optical properties.