A highly efficient UV-emitting Mg₃Y₂Ge₃O₁₂:Bi³⁺ crystal as a fluorescent irradiation source for use in heavy oil viscosity reduction

In this work, we discover and report a type of Mg₃Y₂Ge₃O₁₂:Bi³⁺ crystal that can not only show a highly efficient ultraviolet (UV) luminescence but also be used for reducing the heavy oil viscosity. To fully characterize the photoluminescence (PL) properties of Mg₃Y₂Ge₃O₁₂:Bi³⁺ crystal, various techniques, such as X-ray diffraction, scanning electronic microscope, UV–visible diffuse reflectance and PL spectra, are carried out. Our results reveal that the Mg₃Y₂Ge₃O₁₂:Bi³⁺ crystal features the particle size at ~ 30 µm and an broad Bi³⁺-related emission band peaked at 300 nm upon excitation at 270 nm at the same time. Significantly, although the Mg₃Y₂Ge₃O₁₂:Bi³⁺ crystal only show one emission band, this band can cover almost the whole UV spectral region from 290 to 410 nm, allowing this type of crystal to cover the band gap of TiO₂ semiconductor that has the absorption wavelength of 387 nm and therefore serve as an efficient UV irradiation source for application in the photocatalytic field. As a result, we have designed a ceramic substrate to verify this application, through mixing the TiO₂ semiconductor and Mg₃Y₂Ge₃O₁₂:Bi³⁺ crystal. Our results reveal that the photocatalytic properties of Mg₃Y₂Ge₃O₁₂:Bi³⁺/TiO₂-based ceramic can be greatly enhanced for reducing the heavy oil viscosity (~ 4 times) as compared to the heavy oil that does not involve the Mg₃Y₂Ge₃O₁₂:Bi³⁺/TiO₂-based ceramic.