We report on the demonstration of a new method of thermographic imaging with memory function for sintered Al2O3-ceramics, which is based on the reversible change of the luminescence intensity of the spectral lines at 692.9 nm and 694.3 nm. The intensity of these so-called R-lines, which are attributed to Cr3+-ions in aluminum oxide, is reduced by initial electron-beam irradiation of the ceramic. After subsequent heat exposure, the luminescence intensity recovers permanently again, whereby the amount of increase depends on the temperature and on the duration of the heating process. We show that in the case of a heating time of five minutes, maximum temperatures in the range between 200 °C and 350 °C can be measured after the exposure. The sensitive temperature range can be shifted by adjusting the heating time. Due to the fact that Cr3+ is present in sufficient concentration in commercially available aluminum oxide ceramic products, the sensor function can be introduced by electron irradiation as an intrinsic property of almost any ceramic component. Possible applications and specific advantages in particular with respect to the memory effect are discussed.
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