Effect of crystallite size on electron spin resonance of Gd 3+ and luminescence of Eu 3+ doped in La 6 WO 12

Nano-sized Eu 3+ and Gd 3+ doped lanthanum tungstates of composition La6-xLnxWO12 (Ln = Eu, Gd; 0 � x � 0.2) are prepared by sol-gel complexation method. These samples are characterized by powder X-ray diffraction (XRD). The average crystallite size is calculated from the XRD using Scherer’s equation. The electron spin resonance (ESR) spectrum of Gd 3+ doped lanthanum tungstate (La6WO12) gives characteristic “U” type spectrum. The luminescence spectrum of Eu 3+ doped La6WO12 gives characteristic 5 D0� 7 Fn (n = 0 to 4) bands due to trivalent europium ions. The intensity of 5 D0� 7 F2 transition decreases with increase in the sintering temperature due to depletion of surface Eu 3+ ions. The intensity of 5 D0� 7 F2 sintered at 700°C has highest intensity and may have laser applications.