Structural, optical and special spectral changes of Dy3+ emissions in orthovanadates

Abstract

This paper reports on the structural, optical and photometric characterization of yttrium gadolinium orthovanadates (Y_1−xGd_xVO₄) doped with Dy³⁺ for white emission in solid state lighting. A series of orthovanadates were prepared through a low temperature co-precipitation method and further post annealed. The as synthesized phosphor particles revealed a single phase tetragonal structure with space group I4₁/amd(141). The infrared spectra confirmed the presence of characteristic vibrational bands of orthovanadates. The microscopic images showed elongated particles after annealing and the particle sizes were estimated in the range of 10–50 nm. The band gap of the prepared phosphors, calculated from the corresponding diffuse reflectance spectra was observed to be 3.75 eV and 3.57 eV for YVO₄ and GdVO₄ respectively. Y_1−xGd_xVO₄:Dy³⁺ phosphors, illuminated with ultraviolet light exhibited characteristic blue and yellow luminescence corresponding to ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 transitions of Dy³⁺ ion. The emission spectra showed the variation in the intensity ratio (Y/B) with Gd³⁺ ion variation. Furthermore the thermal quenching property, decay analysis and photometric characterizations were also studied in detail and the results indicated the suitability of these phosphors in solid state lighting.