Polymeric carbon nitride, which was synthesized by polymerization of dicyandiamide at 500°C, was used as a nitridation reagent in the conversion of δ‐alumina (δ‐Al 2 O 3 ) to aluminum nitride (AlN). The products obtained at various reaction temperatures were characterized by powder X‐ray diffraction, 27 Al magic‐angle spinning nuclear magnetic resonance ( MAS NMR ) spectroscopy, Raman spectroscopy, and X‐ray photoelectron spectroscopy ( XPS ). δ‐Al 2 O 3 began to convert to AlN at 900°C, which is the lowest temperature reported for the formation of AlN from Al 2 O 3 , and completely converted to AlN at 1400°C. The occurrence of reaction intermediates during nitridation was confirmed by 27 Al MAS NMR and XPS . The change in Raman spectra with reaction temperatures indicated that lattice defects in AlN were reduced by calcining at higher reaction temperatures.