In this paper, we report the obtention of red-emitting Ca3(PO4)2:Eu3+ phosphor by the solid-state reaction method. X-ray diffraction and photoluminescence (PL) measurements were used to investigate the crystal phases, luminescent properties, and optimal Eu3+ doping concentration. To further improve the PL intensity, Na+ acting as a charge compensator was incorporated into the phosphor. The effects of Na+ concentration on the PL properties were studied. It was found that the charge-compensation phosphor showed greatly enhanced red emission beyond the phosphor without charge compensation. Ca2.3Na0.4(PO4)2:0.3Eu3+ was determined to be the best composition. The charge-compensation mechanism was analyzed in light of the principles on defect formation and reaction, and the changes of the site centrosymmetry for the activator.
Effects of Na+ concentrations on the intensity of red emission. The inset showed the R/O ratios along with Na+ concentrations.