Enhanced emission of encaged-OH‾-free Ca_12(1-x)Sr_12xAl₁₄O₃₃:0.1% Gd³⁺ conductive phosphors via tuning the encaged-electron concentration for low-voltage FEDs

Encaged-OH⁻-free Ca_12(1−x)Sr_12xAl14O₃₃:0.1%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 Ca_11.94Sr_0.06Al₁₄O₃₃:0.1%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.