Enhanced emission of encaged-OH−-free Ca12(1−x)Sr12xAl14O33:0.1%Gd3+ conductive phosphors via tuning the encaged-electron concentration for low-voltage FEDs
Encaged-OH−-free Ca12(1−x)Sr12xAl14O33:0.1%Gd3+ conductive phosphors were prepared through a melt-solidification process in combination with a subsequent heat treatment. Absorption spectra showed that the maximum encaged-electron concentration was increased to 1.08 × 1021 cm−3 through optimizing the doping amount of Sr2+ (x = 0.005). Meanwhile, FTIR and Raman spectra indicated that pure Ca11.94Sr0.06Al14O33:0.1%Gd3+ conductive phosphor without encaged OH− and C22− anions was acquired. For the conductive powders heat-treated in air for different times, the encaged-electron concentrations were tuned from 1.02 × 1021 to 8.3 × 1020 cm−3. ESR, photoluminescence, and luminescence kinetics analyses indicated that the emission at 312 nm mainly originated from Gd3+ ions surrounded by encaged O2− anions, while Gd3+ ions surrounded by encaged electrons had a negative contribution to the UV emission due to the existence of an energy transfer process. Under low-voltage electron-beam excitation (3 kV), enhanced cathodoluminescence (CL) of the conductive phosphors could be achieved by tuning the encaged-electron concentrations. In particular, for the encaged-OH−-free conductive phosphor, the emission intensity of the CL was about one order of magnitude higher than that of the conductive phosphor containing encaged OH− anions. Our results suggested that the encaged-OH−-free conductive phosphors have potential application in low-voltage FEDs.