Abstract: Al NMRand quantum chemistry calculation have been used to study thestructureof γ Al2O3 and AlON. The NMRspectra arecharacterized bythree distinctresonance peaksat114 , 66 and 12 , corresponding to 〔AlN4〕,〔AlO4〕and 〔AlO6〕respectively. The uantum chemistrycalculationsshowqd thatthe models with vacancieslocated at octahedralsitein B block are morestablethanthose with vacancieslocated attetrahedralsitein A blockforboth of γ Al2 O3 and AlON. In AlON, nitrogen atoms preferentially replace oxygen atoms in〔AlO4〕tetrahedrons, and the model with 〔AlN4〕is morestablethan that with 〔AlO4 xNx〕(x= 1 ,2 and 3) and 〔AlO6 - yNy〕(y= 1 ,2 ,3 and 4) , which isin agreement with theexperimental analysisby NMR.

Key words: Al2 O3 and AlON, structure, NMR, quantum chemistrycalculation