Luminescent Eu3+-doped NaLa(WO4)(MoO4) and Ba2CaMoO6 prepared by the modified Pechini method

Abstract

Modified Pechini synthesis routes were developed for synthesis of the novel red phosphor materials NaLa(WO4)(MoO4):Eu3+ and Ba2CaMoO6:Eu3+. Phase pure NaLa(WO4)(MoO4):Eu3+ was obtained at calcination temperatures ≥600 °C using malic acid or tartaric acid as complexing agents. Phase pure Ba2CaMoO6:Eu3+ was attained using EDTA and citric acid, at calcination temperatures ≥800 °C. Choice of complexing agents were discussed on the basis of the solubility of the precursors, metal complex stability constants and conformations of the complexes. The powder properties were characterised using X-ray diffraction, thermal analysis and electron microscopy. Photoluminescence emission intensity was studied as a function of the complexing agents used and calcination temperature of the powders. Maximum emission intensity for NaLa(WO4)(MoO4):Eu3+ was obtained at a calcination temperature of 600 °C, whereas the maximum for Ba2CaMoO6:Eu3+ was obtained after calcination at 1100 °C. Both materials displayed desirable optical properties for use as phosphors in white light-emitting diodes. Phase pure NaLa(WO4)(MoO4):Eu3+ and Ba2CaMoO6:Eu3+ red phosphor materials were synthesised by the modified Pechini route, thus permitting lower calcination temperatures which resulted in increased emission intensity for NaLa(WO4)(MoO4):Eu3+.