LUMINESCENT BORATES, MATERIALS AND ARTICLES INCORPORATING SUCH BORATES, AND METHODS AND APPARATUS

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Embodiments include luminescent materials and associated production methods. The material includes a crystal borate having a first substitutable element and a second substitutable element, one or more rare earth ions substituted for the first substitutable element, and chromium substituted for the second substitutable element. The one or more rare earth ions are selected from a group consisting of neodymium and ytterbium. The material also may include a medium within which particles of the borate are incorporated. The medium, with the luminescent material particles, may form a security feature of an article. Embodiments of methods for identifying whether such a luminescent material is incorporated with an article include exposing a portion of the article to excitation in a chromium absorption band, and determining whether a detected emission produced by the article as a result of the excitation indicates an ytterbium emission after termination of the exposing step.