Photoluminescence properties of La3+ ion-doped YInGe2O7 self-activated phosphor

A color-tunable La3+ ion-doped YInGe2O7 self-activated phosphor has been synthesized using a high energy vibrating milled solid state reaction with metal oxides and calcined at 1200 °C for 10 h in air. The structure and optical properties of (Y1−xLax)InGe2O7 phosphors have been investigated. XRD results show that all the diffraction peaks keep the monoclinic YInGe2O7 phase when the La3+ ion concentration is increased up to 3 mol%. The UV–visible absorption spectra analysis indicated that the intensities of absorption band at 280–450 nm corresponding to the oxygen deficient center of the GeO4 anion were increased and then decreased with increasing the La3+ ion concentrations. Under an excitation of 263 nm, the emission intensities of 487 and 545 nm corresponding to the single ionized VoVo defect emission are increased and then decreased as the La3+ ion concentration is increased. The maximum intensity for these two emission peaks was observed when the La3+ ion concentration is 0.3 mol%. This is due to the lattice distortion and induced an increase in the degree of tensile strain, which causes the amount of oxygen vacancies to increase when the Y3+ ion was substituted by the La3+ ion. In addition, the CIE color coordinates changed from a blue→greenish→bluish region as the La3+ ion concentration increased from 0 to 3 mol%.