Effect of Nd3+ Doping on Structural, Near-Infrared, and Cathodoluminescent Properties for Cadmium Tantalate Phosphors

Cd1-xTa2O6:xNd3+ (x=0.5, 1.5, 3, 5, 7, and 10 mol%) phosphor series were fabricated by conventional solid state method at 1100 °C for 17 hours. The samples of cadmium tantalate were investigated by structural (XRD, SEM) and spectroscopic (CL, PL) analyses. In XRD results, the symmetry of CdTa2O6 phase with orthorhombic columbite structure was confirmed between 0.5 and 10 mol% Nd3+ doping concentrations. SEM analysis of the grains revealed round and shapeless morphology while grain sizes ranged from submicron to several microns. The emission spectra of Cd1-xTa2O6:xNd3+ (x=0.5, 1.5, 3, 5, 7 and 10 mol%) phosphor series recorded with the transitions of 4F3/2→4I9/2 and 4F3/2→4I11/2. Among these transitions, the transition 4F3/2→4I9/2 (at 889 nm) has a high near-infrared emission intensity, which can be attributed to the laser potential of the phosphor. The NIR emission of the phosphor increased with increasing concentration of Nd3+ up to 5 mol% and then declined because of concentration quenching phenomenon. The CL emission peak at about 450 nm found in all samples is related to the intrinsic emission of the cadmium tantalate host. In addition, Nd3+ doped phosphors exhibited the 4F3/2→4I9/2 transition of Nd3+ and defect-related CL emissions at 670 nm. Decreasing crystallinity with increasing Nd3+ concentration caused a decrease in host emission intensity at 450 nm.