A method for determining the amount of a predetermined type of radiation irradiated on a sensor material, wherein the method comprises: a) providing a sensor material; b) exposing the sensor material to the predetermined type of radiation for retaining the predetermined type of radiation in the sensor material for a predetermined period of time; c) subjecting the sensor material, which has been exposed to the predetermined type of radiation, to heat treatment and/or to optical stimulation; and d) determining the amount of visible light emitted by the sensor material as a result of being subjected to the heat treatment and/or to the optical stimulation; characterized in that the sensor material is represented by the following formula (M') 8 (M"M"') 6 O 24 (X,X') 2:M"" formula wherein M' represents a monoatomic cation of an alkali metal selected from Group 1 of the IUPAC periodic table of the elements, or any combination of such cations; M" represents a trivalent monoatomic cation of an element selected from Group 13 of the IUPAC periodic table of the elements, or of a transition element selected from any of Groups 3 - 12 of the IUPAC periodic table of the elements, or any combination of such cations; M"' represents a monoatomic cation of an element selected from Group 14 of the IUPAC periodic table of the elements, or of an element selected from any of Groups 13 and 15 of the IUPAC periodic table of the elements, or of Zn, or any combination of such cations; X represents an anion of an element selected from Group 17 of the IUPAC periodic table of the elements, or any combination of such anions, or wherein X is absent; X' represents an anion of an element selected from Group 16 of the IUPAC periodic table of the elements, or any combination of such anions, or wherein X' is absent; and M"" represents a dopant cation of an element selected from transition metals of the IUPAC periodic table of the elements, or any combination of such cations, or wherein M"" is absent; with the proviso that at least one of X and X' is present. a) providing a sensor material; b) exposing the sensor material to the predetermined type of radiation for retaining the predetermined type of radiation in the sensor material for a predetermined period of time; c) subjecting the sensor material, which has been exposed to the predetermined type of radiation, to heat treatment and/or to optical stimulation; and d) determining the amount of visible light emitted by the sensor material as a result of being subjected to the heat treatment and/or to the optical stimulation; characterized in that the sensor material is represented by the following formula (M') 8 (M"M"') 6 O 24 (X,X') 2:M"" formula wherein M' represents a monoatomic cation of an alkali metal selected from Group 1 of the IUPAC periodic table of the elements, or any combination of such cations; M" represents a trivalent monoatomic cation of an element selected from Group 13 of the IUPAC periodic table of the elements, or of a transition element selected from any of Groups 3 - 12 of the IUPAC periodic table of the elements, or any combination of such cations; M"' represents a monoatomic cation of an element selected from Group 14 of the IUPAC periodic table of the elements, or of an element selected from any of Groups 13 and 15 of the IUPAC periodic table of the elements, or of Zn, or any combination of such cations; X represents an anion of an element selected from Group 17 of the IUPAC periodic table of the elements, or any combination of such anions, or wherein X is absent; X' represents an anion of an element selected from Group 16 of the IUPAC periodic table of the elements, or any combination of such anions, or wherein X' is absent; and M"" represents a dopant cation of an element selected from transition metals of the IUPAC periodic table of the elements, or any combination of such cations, or wherein M"" is absent; with the proviso that at least one of X and X' is present. M' represents a monoatomic cation of an alkali metal selected from Group 1 of the IUPAC periodic table of the elements, or any combination of such cations; M" represents a trivalent monoatomic cation of an element selected from Group 13 of the IUPAC periodic table of the elements, or of a transition element selected from any of Groups 3 - 12 of the IUPAC periodic table of the elements, or any combination of such cations; M"' represents a monoatomic cation of an element selected from Group 14 of the IUPAC periodic table of the elements, or of an element selected from any of Groups 13 and 15 of the IUPAC periodic table of the elements, or of Zn, or any combination of such cations; X represents an anion of an element selected from Group 17 of the IUPAC periodic table of the elements, or any combination of such anions, or wherein X is absent; X' represents an anion of an element selected from Group 16 of the IUPAC periodic table of the elements, or any combination of such anions, or wherein X' is absent; and M"" represents a dopant cation of an element selected from transition metals of the IUPAC periodic table of the elements, or any combination of such cations, or wherein M"" is absent; with the proviso that at least one of X and X' is present.