Phase structure and photoluminescence properties of Er3+-doped Al2O3 powders prepared by the sol–gel method

Abstract

The Er 3+ -doped Al 2 O 3 powders have been prepared by the sol–gel method, using the aluminium isopropoxide [Al(OC 3 H 7 ) 3 ]-derived Al 2 O 3 sols with addition of the erbium nitrate [Er(NO 3 ) 3 · 5H 2 O]. The different phase structure, including three crystalline types of (Al,Er) 2 O 3 phases, γ, θ, α, and two Er–Al–O phases, ErAlO 3 and Al 10 Er 6 O 24 , was obtained with the 0–5 mol% Er 3+ -doped Al 2 O 3 powders at the different sintering temperature of 600–1200 °C. The phase structure has an evident influence on the photoluminescence (PL) properties for the Er 3+ -doped Al 2 O 3 powders. For the phase mixture of γ-(Al,Er) 2 O 3 and θ-(Al,Er) 2 O 3 in minor amounts with the different Er 3+ doping concentration sintered at 900 °C, 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 2 O 3 powders increased with the phase structure changed from γ-(Al,Er) 2 O 3 → θ-(Al,Er) 2 O 3 → α-(Al,Er) 2 O 3 , corresponding to the increase of sintering temperature from 600 to 1200 °C. 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 6 O 24 phases prepared at 1200 °C.