Sr2+ substitution for Ca2+ and Eu2+,Dy3+ co-doping enhance mechanoluminescence of CaAl2Si2O8 phosphors

A series of phosphors (Ca1-xSrx)Al2Si2O8:Eu2+,Dy3+ (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.8) and Ca0.6Sr0.4Al2Si2O8:yEu2+,2yDy3+ (y = 0.005, 0.01, 0.015, 0.02) were prepared. It was found Ca0.6Sr0.4Al2Si2O8:Eu2+,Dy3+ achieved the highest mechanoluminescence intensity, and the optimal Eu2+ and Dy3+ co-doping contents were 1% and 2%, respectively. The emission peak of Ca0.6Sr0.4Al2Si2O8:0.01Eu2+,0.02Dy3+ was located at 413 nm on ML spectrum, which was similar to the photoluminescence, indicating both mechanoluminescence and photoluminescence were attributed to the 4f65 d1→4f7 transition of Eu2+. Also Ca0.6Sr0.4Al2Si2O8:0.01Eu2+,0.02Dy3+ exhibited an excellent threshold force (130 N) in the extremely broad tested force range (130-3000 N) and kept a nearly perfect linear response, which made it a potential candidate for application of pressure sensors. The introduction of Sr2+, Eu2+ and Dy3+ caused lattice distortion, formation of more defects, and thus generation of more suitable traps to capture the electronic carriers under ultraviolet excitation. Increasing the number of traps and tuning of the trap depth were found to increase the mechanoluminescence response.