Luminescent phosphor compounds, articles including such compounds, and methods for their production and use

Abstract

Embodiments include luminescent phosphor compounds that include one or more emitting ions and one or more disturbing ions, and methods for their production. An emitting ion in the compound may be characterized by a first decay time constant when the emitting ion is undisturbed. However, a corresponding disturbing ion in the compound, which is different from the emitting ion, causes the emitting ion to have a pre-defined, target disturbed decay time constant that is greater than zero and less than the first decay time constant. An embodiment of an authentication system is configured to measure the decay time constant of a phosphor compound applied to an article, and to determine whether the decay time constant corresponds to a phosphor compound that includes a particular disturbing ion (e.g., in order to determine whether or not the article is authentic).

1 . A luminescent phosphor compound for security applications comprising:
 one or more emitting ions and one or more disturbing ions, wherein the one or more emitting ions have one or more first decay time constants when the one or more emitting ions are undisturbed, the one or more disturbing ions are different from the one or more emitting ions, and the one or more disturbing ions are included in the phosphor compound in a quantity that will cause at least one of the one or more emitting ions to have a pre-defined, target disturbed decay time constant that is greater than zero and less than a corresponding one of the one or more first decay time constants, and wherein the first decay time constant and the target disturbed decay time constants can be distinguished by an authentication device.   
     
     
         2 . The luminescent phosphor compound of  claim 1 , wherein the one or more emitting ions include one or more ions of one or more elements selected from a group consisting of chromium, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and ytterbium. 
     
     
         3 . The luminescent phosphor compound of  claim 1 , wherein the one or more disturbing ions include one or more ions of one or more elements selected from a group consisting of chromium, manganese, cerium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, iron, cobalt, and nickel. 
     
     
         4 . The luminescent phosphor compound of  claim 1 , wherein the one or more disturbing ions include one or more ions of one or more elements selected from a group consisting of praseodymium, samarium, europium, terbium, and dysprosium. 
     
     
         5 . The luminescent phosphor compound of  claim 1 , wherein one or more disturbing ions cause the at least one of the one or more emitting ions to have the target disturbed decay time constant by absorbing energy discharged by the at least one of the one or more emitting ions in transitioning from a storage level to a lower energy level, and by discharging the energy non-radiatively. 
     
     
         6 . The luminescent phosphor compound of  claim 1 , wherein at least one of the one or more first decay time constants is in a range of 0.5 milliseconds to 10 milliseconds. 
     
     
         7 . The luminescent phosphor compound of  claim 1 , wherein the target disturbed decay time constant is in a range of 0.2 milliseconds to 8 milliseconds. 
     
     
         8 . The luminescent phosphor compound of  claim 1 , wherein the target disturbed decay time constant is within a range of 20 to 80 percent of at least one of the one or more first decay time constants. 
     
     
         9 . The luminescent phosphor compound of  claim 1 , wherein the luminescent phosphor compound further comprises:
 one or more additional emitting ions, which have one or more additional first decay time constants when the one or more additional emitting ions are undisturbed, wherein the one or more disturbing ions or one or more additional disturbing ions cause at least one of the one or more additional emitting ions to have one or more additional, pre-defined target disturbed decay time constants that are greater than zero and less than corresponding ones of the one or more additional first decay time constants.   
     
     
         10 . The luminescent phosphor compound of  claim 1 , wherein the luminescent phosphor compound further comprises:
 one or more additional disturbing ions, wherein the one or more disturbing ions or the one or more additional disturbing ions cause at least one of the one or more emitting ions or one or more additional emitting ions, which have one or more additional first decay time constants when the one or more additional emitting ions are undisturbed, to have one or more additional, pre-defined target disturbed decay time constants that are greater than zero and less than corresponding ones of the one or more additional first decay time constants.   
     
     
         11 . The luminescent phosphor compound of  claim 1 , further comprising a phosphor host crystal lattice material selected from a group consisting of an oxide, a fluoride, an oxysulfide, a halide, a borate, a silicate, a gallate, a phosphate, a vanadate, an oxyhalide, an aluminate, a molybdate, a tungstate, a garnet, a niobate, and a combination of the aforementioned host crystal lattice materials. 
     
     
         12 . A method for producing a luminescent phosphor compound comprising the steps of:
 obtaining a baseline phosphor compound that includes a phosphor host crystal lattice material, one or more emitting ions, and a quantity of rare earth impurities, wherein the baseline phosphor compound is characterized by one or more first decay time constants;   synthesizing a disturbed phosphor compound that includes the phosphor host crystal lattice material, the one or more emitting ions, the quantity of rare earth impurities, and a quantity of one or more disturbing ions;   measuring one or more second decay time constants of the disturbed phosphor compound;   determining whether the one or more second decay time constants are substantially equal to one or more target disturbed decay time constants that are greater than zero and less than corresponding ones of the one or more first decay time constants; and   when at least one of the one or more second decay time constants is not substantially equal to the one or more target disturbed decay time constants, repeating the synthesizing, measuring, and determining steps for an additional candidate disturbed phosphor compound that has an adjusted quantity of the one or more disturbing ions that is different from the initial quantity.   
     
     
         13 . The method of  claim 12 , wherein repeating the synthesizing step comprises:
 increasing the quantity of the one or more disturbing ions when the one or more second decay time constants are greater than the one or more target disturbed decay time constants; and   decreasing the quantity of the one or more disturbing ions when the one or more second decay time constants are less than the one or more target disturbed decay time constants.   
     
     
         14 . The method of  claim 12 , wherein the one or more emitting ions include one or more ions elements selected from a group consisting of chromium, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and ytterbium. 
     
     
         15 . The method of  claim 12 , wherein the one or more disturbing ions include one or more ions of elements selected from a group consisting of chromium, manganese, cerium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, iron, cobalt, and nickel. 
     
     
         16 . An article comprising:
 a substrate; and   an authentication feature on a surface of the substrate or integrated within the substrate, wherein the authentication feature includes a luminescent phosphor compound comprising one or more emitting ions and one or more disturbing ions, wherein the one or more emitting ions have one or more first decay time constants when the one or more emitting ions are undisturbed, and the one or more disturbing ions are different from the one or more emitting ions, and the one or more disturbing ions are included in the phosphor compound in a quantity that will cause at least one of the one or more emitting ions to have a pre-defined, target disturbed decay time constant that is greater than zero and less than a corresponding one of the one or more first decay time constants.   
     
     
         17 . The article of  claim 16 , wherein the article is selected from a group consisting of an identification card, a driver's license, a passport, identity papers, a banknote, a check, a document, a paper, a stock certificate, a packaging component, a credit card, a bank card, a label, a seal, a postage stamp, a liquid, a human, an animal, and a biological sample. 
     
     
         18 . The article of  claim 16 , wherein the substrate includes one or more materials selected from a group consisting of paper, a polymer, glass, a metal, a textile, and a fiber. 
     
     
         19 . The article of  claim 16 , wherein the one or more emitting ions include one or more ions elements selected from a group consisting of chromium, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and ytterbium. 
     
     
         20 . The article of  claim 16 , wherein the one or more disturbing ions include one or more ions of elements selected from a group consisting of chromium, manganese, cerium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, iron, cobalt, and nickel.