Rapid phase mapping in heat‐treated powder mixture of alumina and magnesia utilizing cathodoluminescence

Scanning electron microscope – cathodoluminescence (SEM ‐ CL) analysis was carried out for the rapid phase identification of a single particle with the size of approximately 100 µm consisting of alumina (Al 2 O 3 ) and spinel (MgAl 2 O 4 ) phases. We selected this particle as the analyte because Al 2 O 3 and MgAl 2 O 4 are typical inclusions in steel, and their identification is important for steel production. Samples were prepared by pressing a mixture of Al 2 O 3 and magnesia (MgO) powders heated at 1300 °C and copper powder into a pellet. The formation of a MgAl 2 O 4 phase in the powder mixture of Al 2 O 3 and MgO heated at 1300 °C was confirmed by X‐ray diffraction analysis. CL images of samples were obtained using a camera attached to a SEM. We confirmed that Al 2 O 3 and MgAl 2 O 4 phases in a CL image produced blue and green luminescence, respectively, by comparing the CL image with elemental mappings of aluminum and magnesium in the sample obtained using an energy‐dispersive X‐ray detector attached to a SEM. We also observed the shift of a phase boundary between Al 2 O 3 and MgAl 2 O 4 with dozen micrometers scale by obtaining CL images of samples containing a mixture of Al 2 O 3 and MgO powders heated at 1300 °C with different heat‐treatment durations. The time required to obtain a CL image was 1 s. Thus, SEM‐CL analysis will contribute to the rapid phase identification of Al 2 O 3 and MgAl 2 O 4 in a single particle. Copyright © 2017 John Wiley & Sons, Ltd.