X-ray absorption near edge structure (XANES) measurements at the Si and N K-edges of ternary Si-C-N compounds are applied to analyze the changes of structural units owing to the thermally induced ceramization of silicon dicarbodiimide Si(N=C=N)₂ at temperatures up to 1600°C. Samples synthesized below 800°C show an environment of silicon consisting of carbodiimide (N=C=N) groups. Further annealing leads to a crystalline phase, Si₂CN₄, which combines the structural units (Si-N-Si) and (Si-N=C=N). Recorded spectra of samples annealed at temperatures higher than 1200°C show the decomposition of Si₂CN₄. The material then transforms to a Si₃N₄-SiC composite material through an intermediate amorphous Si-C-N phase.