Phase structure and photoluminescence properties of Er~(3+) -doped Al_2O_3 powders prepared by the sol-gel method

摘要

The Er~(3+)-doped Al_2O_3 powders have been prepared by the sol-gel method, using the aluminium isopropoxide [Al(OC_3H_7)_3]-derived Al_2O_3 sols with addition of the erbium nitrate [Er(NO_3)_3 · 5H_2O]. The different phase structure, including three crystalline types of (Al,Er)_2O_3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO_3 and Al_(10)Er_6O_(24), was obtained with the 0-5 mol% Er~(3+)-doped Al_2O_3 powders at the different sintering temperature of 600-1200℃. The phase structure has an evident influence on the photo-luminescence (PL) properties for the Er~(3+)-doped Al_2O_3 powders. For the phase mixture of γ-(Al,Er)_2O_3 and θ-(Al,Er)_2O_3 in minor amounts with the different Er~(3+) doping concentration sintered at 900 ℃, the PL spectra of the full widths at half maximum (FWHM) of about 55 nm were observed with a main peak at λ= 1.533 μm and a side peak at λ = 1.549 μm. The stronger PL intensity was detected with the 0.5 and 1 mol% Er~(3+) doping concentration, and decreased with further increasing the Er~(3+) doping concentration. The dramatic concentration quenching effect took place above the 1.5 mol% Er~(3+) doping concentration. At the 1 mol% Er~(3+) doping concentration, the PL intensity of the Er~(3+)-doped Al_2O_3 powders increased with the phase structure changed from γ-(Al,Er)_2O_3→ θ-(Al,Er)_2O_3 →α-(Al,Er)_2O_3, corresponding to the increase of sintering temperature from 600 to 1200 ℃. The PL spectrum was observed with the main sharp peak at λ = 1.533 μm and many sharp side peaks at the different wavelengths for the α-(Al,Er)_2 O_3, ErAlO_3 and Al_(10)Er_6O_(24) phases prepared at 1200 ℃.