Low-temperature synthesis of SrAl2O4 by a modified sol–gel route: XRD and Raman characterization

Among other alkaline-earth aluminates, the monoclinic (M) polymorph of SrAl2O4 can be used as host material for Eu2+ luminescence based phosphors. With the aim of reducing the synthesis temperature of this polymorph, we have produced and characterized by XRD and Raman scattering solid solutions of the SrAl2−xBxO4 system (image) obtained by two different methods, a ceramic route and a modified sol–gel synthesis. Though the addition of boron lowers the temperature of obtention of the M polymorph in both type of samples, lower B contents are needed to stabilize the M form as single phase for samples prepared by the sol–gel method than through the ceramic route. In the sol–gel method, the M polymorph can be obtained at temperatures as low as 1200 °C, with a Boron content of just 1%. Rietveld profile analysis allows us to conclude that coexistence of the monoclinic and hexagonal polymorphs of SrAl2O4 occurs for samples synthesized below an onset temperature of about 1000–1100 °C, that depends on the sample composition. Above those temperatures, only the monoclinic phase is formed.