Thermoluminescent composite particle and marking comprising same

A composite particle for use in a marking, wherein the composite particle comprises a thermoconductive material matrix comprising two or more superparamagnetic cores embedded therein, each of the two or more superparamagnetic cores consisting of one or more superparamagnetic materials selected from iron oxide, metallic Fe, metallic Co, metallic Ni and metal alloys, and the matrix is surrounded by a thermoluminescent portion present in the form of a shell around the matrix in which the two or more superparamagnetic cores are embedded, or of an aggregate of thermoluminescent particles which are randomly distributed around the matrix in which the two or more superparamagnetic cores are embedded, the thermoluminescent portion consisting of two or more doped ceramic materials, each of the two or more doped ceramic materials being selected from the following:

• Ba2MgSi2O7, Ba2Si3O8, Ba2SiO, Ba2ZnSi2O7, Ba5Si8O21, BaSi2O5, BaSiO3, CaGd2Si2O7, Li2CaSiO4, NaLaSiO4, BaAl10MgO17, BaAl12O19, BaHfO3, CaHf3, GdSc2Al3O12, Gd3Y3Al10O24, La2O3, LaAlO3, SrHfO3, Ba2B5O9Cl, Ba2Ca(BO3)2, Ba3Gd(BO)3, Ca4YO(BO3)3, CaLaB7O13, CaYBO4, GdB3O6, GdBO3, LaB3O6, Li6Gd(BO3)3, Li6Y(BO3)3, YAl3B4O12, AgGd(PO3)4, Ba3(PO4)2, Ba3B(PO4)3, Ba3P4O13, Ba5(PO4)3F, BaKPO4, BaP2O6, CaBPO5, CeP5O14, CsGd(PO3)4, CsLuP2O7, CsYP2O7, K3Lu(PO4)2, KGd(PO3)4, LuP2O7, KYP2O7, LiCaPO4, LiGd(PO3)4, LuPO4, NaBaPO4, NaGd(PO3)4, NaLuP2O7, RbLuP2O7, RbYP2O7, Gd2S3, Lu2S3, CaSnO3, and ZnTa2O6, each doped with at least one doping ion selected from Eu2+, Eu3+, Dy3+, Pr3+, Sm3+, Tb3+, Ce3+, Ce2+, Er3+, Tm3+, Cr3+, Mn2+, and Ti3+,
• wherein the composite particle has a spherical or rod-like shape,
• wherein the thermoconductive material comprises one or more of SiO2, TiO2, and polymethylmethacrylate,
• wherein the two or more doped ceramic materials are selected such that they provide distinct glow curves, wherein a glow curve of each of the two or more doped ceramic materials is obtained by plotting an intensity of radiation emitted by the ceramic material versus time of applying an oscillating magnetic field to the superparamagnetic materials of the composite particle.