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

The Er3+-doped Al2O3 powders have been prepared by the sol–gel method, using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with addition of the erbium nitrate [Er(NO3)3 · 5H2O]. The different phase structure, including three crystalline types of (Al,Er)2O3 phases, γ, θ, α, and two Er–Al–O phases, ErAlO3 and Al10Er6O24, was obtained with the 0–5 mol% Er3+-doped Al2O3 powders at the different sintering temperature of 600–1200 °C. The phase structure has an evident influence on the photoluminescence (PL) properties for the Er3+-doped Al2O3 powders. For the phase mixture of γ-(Al,Er)2O3 and θ-(Al,Er)2O3 in minor amounts with the different Er3+ 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 <f>λ=1.533</f> μm and a side peak at <f>λ=1.549</f> μm. The stronger PL intensity was detected with the 0.5 and 1 mol% Er3+ doping concentration, and decreased with further increasing the Er3+ doping concentration. The dramatic concentration quenching effect took place above the 1.5 mol% Er3+ doping concentration. At the 1 mol% Er3+ doping concentration, the PL intensity of the Er3+-doped Al2O3 powders increased with the phase structure changed from γ-(Al,Er)2O3 → θ-(Al,Er)2O3 → α-(Al,Er)2O3, corresponding to the increase of sintering temperature from 600 to 1200 °C. The PL spectrum was observed with the main sharp peak at <f>λ=1.533</f> μm and many sharp side peaks at the different wavelengths for the α-(Al,Er)2 O3, ErAlO3 and Al10Er6O24 phases prepared at 1200 °C. [Copyright &y& Elsevier]