Red emitting SrTiO_3 : Pr, Al phosphors were synthesized by sol-gel method, the effect of Al on the luminescent properties of the phosphors were investigated. CL luminance and chromaticity of the red emission were improved with increasing Al contents up to 30mol%. The phosphor with a Al content of 30mol% showed 33cd/m^2 under excitation at 2kV and 108μA/cm^2. It was found from the measurements of SEM and NMR that almost of Al is distributed homogeneously as Al_2O_3 on the phosphor surface. Moreover, it was suggested from the measurements of XRD and NMR that new formation of tetrahedral Al-O bond might be concerned with the emission.
