Effect of crystallite size on electron spin resonance of Gd~(3+) and luminescence of Eu~(3+) doped in

摘要

Nano-sized Eu~(3+) and Gd~(3+) doped lanthanum tungstates of composition La_(6-x)Ln_xWO_(12) (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 (La_6WO_(12)) gives characteristic "U" type spectrum. The luminescence spectrum of Eu~(3+) doped La_6WO_(12) gives characteristic ~5D_0->~7F_n (n = 0 to 4) bands due to divalent europium ions. The intensity of ~5D_0->~7F_2 transition decreases with increase in the sintering temperature due to depletion of surface Eu3+ ions. The intensity of ~5D_0->~7F_2 sintered at 700°C has highest intensity and may have laser applications.