文摘
Color point tuning is an important challenge for improving the practical applications of various displays, especially there are very limited white color single hosts that emits in the white spectrum. In this paper, the possibility of color tuning by substituting part of host lattice cation (Sr2+ ions) by Ca2+ or Ba2+ ions in an efficient strontium aluminate phosphor, Sr4Al14O25:Eu2+,Dy3+, is reported and found to be very promising for displays. A detail study by replacing part of Sr2+ with Ca2+ or Ba2+ has been investigated. X-ray diffraction study showed that crystal structure of Sr4Al14O25 is preserved up to 20 mol of Ca2+ ion exchange while it is limited to 10 mol of Ba2+ ions exchange. Substantial shift in the emission band and color were observed by substitution of Sr2+ by Ca2+ or Ba2+ ions. A bluish-white emission and afterglow was observed at higher Ca2+ ions substitution. Further, partial Ca2+ substitutions (up to 0.8 mol) resulted in enhanced afterglow of Sr4Al14O25:Eu2+,Dy3+ phosphor. However, Ba2+ substitution decreased the fluorescence as well afterglow of the Sr4Al14O25:Eu2+,Dy3+ phosphor significantly. The enhanced phosphorescence by partial Ca2+ substitution is explained on the basis of increased density of shallow traps associated with higher solubility of Dy3+ ions in to the host lattice due to equivalent size of Ca2+ and Dy3+ ions. Thus, Ca2+ substitution in the Sr4Al14O25:Eu2+,Dy3+ phosphor is a promising method for tuning the emission color and improving the afterglow intensity of the phosphor.
