Effects of high-temperature annealing on structural and optical properties of highly ordered porous alumina membranes

We report on the structural and optical properties of highly ordered porous alumina membranes (PAMs) under different annealing temperatures up to 1100 ° C . Clear structural transition from amorphous to γ - and then to α - Al 2 O 3 has been demonstrated in PAMs through x-ray diffraction and micro-Raman scattering measurements. The crystallization of the PAMs under an annealing temperature above 800 ° C results in the appearance of two absorption structures in the transmission spectra ranging from 1500 to 1700 cm − 1 due to the formation of stable carboxylic impurities. We have presented convincing evidence that the blue photoluminescence band in PAMs originates from the coactions of the singly ionized oxygen vacancies ( F + centers) and the luminescent centers transformed from oxalic impurities.