Photoemission during flash sintering: An interpretation based on thermal radiation

Optical emission spectra were recorded in the range 180–1700 nm during flash sintering of alumina and magnesia silicate glass-containing alumina. The collected spectra, corrected for taking care of instrumental effects, are consistent with thermal radiation effect. A partial exception is represented by the lower density samples treated with low current density, whose spectrum shows very small deviation from the expected thermal radiation at ∼680 nm although the corresponding physical phenomenon remains unclear. In any case, the overall photoemission upon flash sintering can be substantially associated with Joule heating, in all tested conditions, with no effect of any other previously reported mechanism like electroluminescence.