Rietveld Refinement, Morphology, and Optical and Photoluminescence Properties of a β-Ag_1.94Cu_0.06MoO₄ Solid Solution

Corner-truncated cubic β-Ag_1.94Cu_0.06MoO₄ microcrystals were synthesized using the hydrothermal method. These were investigated by X-ray diffraction, confirming obtention of the spinel structure Fd3̅m. Through Raman spectroscopy are confirmed all modes for the point group of O⁷. The E_gap shows a decrease of the band gap from 3.20 to 3.07 eV, with reduction of the conduction band occurring from -0.20 eV (β-Ag₂MoO₄) to -0.13 eV (β-Ag_1.94Cu_0.06MoO₄), suggesting a p-type behavior for the Cu²⁺ ion. The field-emission scanning electron microscopy images confirm the morphological changes for β-Ag₂MoO₄, where potato-like microcrystals were found. Meanwhile, corner-truncated cubic microcrystals for β-Ag_1.94Cu_0.06MoO₄. The photoluminescence (PL) spectrum confirms the increase in the PL emission for β-Ag_1.94Cu_0.06MoO₄, with suppression of the deep defects occurring in the structure caused by oxygen and silver atoms. In contrast, the green region is intensified because of distortions of the Ag-O and Mo-O bonds. Therefore, the β-Ag_1.94Cu_0.06MoO₄ solid solution has PL emission with CCT (4510 K) and CIE coordinates (x = 0.372 and y = 0.433), which could be interesting properties for applications as light-emitting diodes.