The nature of Bi3+ luminescence in melilite-structure gallate ABGa3O7 (A = Ca, Sr, Ba; B = La, Gd)

It is of great significance to achieve precise luminescence regulation of Bi3+-activated phosphor by adjusting crystallographic environment of Bi3+ ions. In this study, a series of Bi3+ activated melilite-structure gallate ABGa3O7 (A = Ca, Sr, Ba; B = La, Gd) phosphors was successfully synthesized via solid-state reaction method. Using SrGdGa3O7:Bi3+ as a representative, the crystal structure and photoluminescence properties were studied. The emission of ABGa3O7:Bi3+ adjustable from blue to cyan light can be reached by replacing A and B atoms. The structural characteristics of ABGa3O7 were explored using geometry optimization calculations and Rietveld refinement. The relations between the transformation of Bi3+ environment and the luminescence behavior are deduced by combining theoretical calculations and experimental results. The results show that the contraction, broadening and shift of excitation and emission spectra of ABGa3O7:Bi3+ depend on the bond length and distortion of polyhedra as well as the number of luminous centers. It is hoped that this study can provide some insights for the development and modification of a novel Bi3+ activated gallate phosphors.