Effects of Eu3+ doping on the luminescence properties of novel Sr2CaLa(VO4)3 from partial substitution of Sr2+ by Ca2+ in Sr3La(VO4)3

Abstract Eu3+-activated Sr3−xCaxLa(VO4)3 phosphors were fabricated via citric-acid-assisted sol combustion. Characterization of the Sr3−xCaxLa(VO4)3:Eu3+ samples with different concentrations of Ca2+ revealed a hexagonal crystal structure belonging to the R-3m space group. The amount of Ca2+ added (x) was controlled within 0 ≤ x ≤ 2 to yield high-purity phosphors. Scanning electron microscopy results showed that an increase in Ca2+ concentration resulted in a decrease in the particle size of Sr3−xCaxLa(VO4)3:Eu3+, with the shape gradually changing from nearly equiaxed to lath-shaped. The Sr2CaLa(VO4)3:Eu3+ phosphor (denoted as SCLVO:Eu3+) exhibited the strongest photoluminescence (PL) intensity at 618 nm among the samples under excitation of 394-nm near-UV (NUV) light. The study of Eu3+ doping concentration confirmed that Eu3+ could enter the lattice of the SCLVO matrix without altering its crystal structure. SCLVO:Eu3+ was found to strongly absorb 394 nm NUV light and 464 nm blue light. The optimal concentration of the Eu3+ dopant in the SCLVO host was 0.11, which resulted in the phosphor achieving an excellent PL intensity and a color purity of 98.68%. Tunable luminescence from the orange area (0.5280, 0.4522) of Commission Internationale de l'eclairage (CIE) to the red area (0.6313, 0.3650) was achieved by adjusting the concentration of Eu3+. Under 394 nm excitation, SCLVO:0.11Eu3+ phosphor has a quantum yield (QY) of 28.2% and excellent thermal stability with 0.383 eV activation energy. Consequently, White-light-emitting diode (WLED) based on SCLVO:0.11Eu3+ phosphor yielded a high color rendering index (CRI), low correlated color temperature (CCT), and CIE coordinates of 91.8, 5196 K, and (0.3407, 0.3612), respectively, under the 20 mA driven current. These results indicated the tremendous potential of SCLVO:0.11Eu3+ phosphors for application in WLEDs excited by NUV or blue light.