Enhanced luminescence performances of Mn~(4+)-activated Sr_4Al_(14)O_(25) red phosphors by doping with Sc~(3+) ions

A series of non-rare earth Mn⁴⁺-activated strontium aluminate phosphors Sr₄Al₁₄O₂₅:Mn⁴⁺ co-doped with Sc³⁺ ions were successfully synthesized by a high-temperature solid-state reaction method. XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc³⁺ ions. Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light, and a deep red emission centered at 652 nm with a narrow full width at half maximum (FWHM) can be obtained, which is attributed to the transition ²E→⁴A₂ of Mn⁴⁺ ions. In addition, the crystal field strength parameter (D_q) and Racah parameters (B, C) and energies of states were calculated based on experimental data. Moreover, the luminous intensity of Sr₄Al_14-xSc_xO₂₅:Mn⁴⁺ is enhanced and increased by 60% compared with Mn⁴⁺ single incorporated sample at x = 0.06. A phenomenon of redshift is observed in the excitation spectrum and discussed systematically. Finally, the mechanism of the positive effects with Sc³⁺ ions incorporated into lattice is discussed in detail. All the results suggest that the Sr₄Al_13.94Sc_0.06O₂₅:Mn⁴⁺ phosphor will become one of the great candidates for backlight of LCD.