Effects of oxygen vacancies on luminescent properties of phosphor Sr4Al14O25:Mn4+ co-doping with alkali metal ion

A series of Na+, Mn4+ ions co-doped Sr4Al14O25 phosphors are synthesized by conventional solid-state reaction and their luminescent properties are investigated in detail. XRD result reveal that there is no introduction of additional phase with incorporation of Na+ 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. The ESR result shows that doping Na+ ions can lead to the creation of the oxygen vacancies due to the nonequivalent substitution between Na+ ions and Sr2+ ions, the oxygen vacancies can act as a sensitizer for the effective energy transfer from Sr4Al14O25 host to Mn4+ ions. Correspondingly, a possible mechanism for energy transfer between oxygen vacancies and Mn4+ is provided. The luminous intensity of Sr4-xNaxAl14O25-x/2: Mn4+ is enhanced and increase by 250% compared with Mn4+ single incorporated sample at x = 0.6. All the results suggest that this phosphor could be considered as a potential red phosphor for the backlight of LCD.