Thermochromoluminescent Mn2+-Doped oxides as thermal sensor for selective laser sintering

Abstract Mn2+-doped Zn3(PO4)2 and Mn2+-doped ZnAl2·2O4+δ compounds were prepared from solid state route and Pechini process, respectively. The luminescent properties evolution of both as-prepared powder compounds versus the annealing temperature (for 10 min annealing treatments) was studied, in the range 500–1400 °C. In parallel, Doctor Blade was used to prepare few micron-thick films for laser irradiation with the 1 μm wavelength laser of our SLS process (Selective Laser Sintering process). The ultra-rapid heating produces by laser irradiation induces on the films very different optical properties evolution in comparison to what was observed for the powder samples annealed into furnaces for the Mn-doped zinc phosphate. On the opposite, for the spinel compound, whatever the heating process (laser on film or furnace for powder samples), the modification of the luminescence properties is directly linked in a same way to the maximum temperature gained during the thermal history. The idea is to use thermal sensor to extract the temperature map of a film while it is subjected to laser irradiation as during SLS process. The study shows that thermal sensors must rely on mechanisms which remain effective even for ultra-rapid heating: a cationic redistribution versus temperature as occurring into spinel matrix is one solution proposed. But changes in the chromaticity resulting from phase transition between different allotropic forms as occurring into the zinc phosphate compound cannot be directly exploited.