Phase identification in g- and k-alumina coatings by cathodoluminescence

Cathodoluminescence (CL) properties were studied for metastable g- and K-Al@d2O@d3 coatings for cutting tool inserts. The alumina films demonstrate a strong CL, with peak energies depending on the Al@d2O@d3 polymorphs. The phase transformation caused by heat treatment is shown to correlate with strong CL modification in the annealed coatings. Spatially resolved CL is found to be a powerful nondestructive technique for identification of different alumina phases on the microscopic level. The corresponding optical properties of g- and K-Al@d2O@d3 are discussed.