PHASE-SEPARATION IN THE SIC-ALN PSEUDOBINARY SYSTEM - THE ROLE OF COHERENCY STRAIN-ENERGY

SiC-AlN polycrystalline samples of equimolar composition were fabricated by hot-pressing. Single-phase samples were annealed over a range of temperatures between 1600-degrees and 2000-degrees-C for up to 1145 h to effect the formation of modulated structures. Electron diffraction from the [2110BAR] zone axis showed four distinct satellite spots around every main diffraction spot with modulations occurring orthogonal to {0112BAR} planes. The direction of modulation experimentally observed is consistent with that determined by the minimization of the coherency strain energy. Computer simulation was conducted to generate the morphology of modulated structures. The simulated microstructure was found to be very similar to that observed experimentally.