Coherent effect of Er3+–Yb3+ co-doping on enhanced photoluminescence properties of Al2O3 powders by the sol–gel method

Abstract The Er 3+ –Yb 3+ co-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 the addition of erbium nitrate [Er(NO 3 ) 3  · 5H 2 O] and ytterbium nitrate [Yb(NO 3 ) 3  · 5H 2 O]. The phase structure, including only two crystalline types of Al 2 O 3 phases, γ and θ, was obtained for the 0–1 mol% Er 3+ and 0–2 mol% Yb 3+ co-doped Al 2 O 3 powders at the different sintering temperature of 800–1000 °C. The evidence for indirect pumping of Er 3+ through transfer of energy from Yb 3+ was found in the Al 2 O 3 matrix material. For the 0.5 mol% Er 3+ and 0.5 mol% Yb 3+ , the 1.0 mol% Er 3+ and 1.0 mol% Yb 3+ co-doped Al 2 O 3 powders, the photoluminescence (PL) peak intensity at 1.533 μm in the spectra increased by a factor of about 2, and the corresponding full widths at half maximum (FWHM) was increased to about 59 nm, compared with that of the 0.5 and 1 mol% Er 3+ -doped Al 2 O 3 powders, respectively. At the same Er 3+ –Yb 3+ co-doping concentration, the PL intensity increased with increasing the sintering temperature from 800 to 1000 °C. Coherent effect of Er 3+ –Yb 3+ co-doping on enhanced PL properties of Al 2 O 3 powders was observed. A proper molar ratio of 1:1 for Yb 3+ and Er 3+ led to the maximum PL intensity at the same sintering temperature.