The Er 3þ -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 AE 5H 2 O]. The different phase structure, including three crystalline types of (Al,Er) 2 O 3 phases, c, h, a, and two Er-Al-O phases, ErAlO 3 and Al 10 Er 6 O 24 , was obtained with the 0-5 mol% Er 3þ -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 3þ -doped Al 2 O 3 powders. For the phase mixture of c-(Al,Er) 2 O 3 and h-(Al,Er) 2 O 3 in minor amounts with the different Er 3þ 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 k ¼ 1:533 lm and a side peak at k ¼ 1:549 lm. The stronger PL intensity was detected with the 0.5 and 1 mol% Er 3þ doping concentration, and decreased with further increasing the Er 3þ doping concentration. The dramatic concentration quenching effect took place above the 1.5 mol% Er 3þ doping concentration. At the 1 mol% Er 3þ doping concentration, the PL intensity of the Er 3þ -doped Al 2 O 3 powders increased with the phase structure changed from c-(Al,Er) 2 O 3 fi h-(Al,Er) 2 O 3 fi a-(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 k ¼ 1:533 lm and many sharp side peaks at the different wavelengths for the a-(Al,Er) 2 O 3 , ErAlO 3 and Al 10 Er 6 O 24 phases prepared at 1200 °C.