A new type of silicogermanate phosphor with excellent persistent luminescence characteristics at room and low temperatures

Near-infrared (NIR) long persistent luminescent materials, with broad potential applications, have attracted significant research interest, though most studies focus on room-temperature performance. However, designing and synthesizing long-persistent luminescent materials that can form a large number of stable shallow traps at lower temperatures is extremely challenging. In this paper, a series of Cr-doped broadband near-infrared silicon germanate long persistent luminescent phosphors were synthesized by the high-temperature solid-phase method. The optical properties and crystal structural parameters of the phosphors at room temperature were studied systematically. The specific luminescence sources and reasons for the broadening of emission peaks have been discussed. The significant differences in persistent luminescence at different temperatures are caused by the substitution of Ge-Si chemical units in the Na₂CaGe x Si 6-x O₁₄ matrix doped with Cr³⁺ ions. Among the samples, Na 2 CaGe 4 Si 2 O 14 :0.4 mol% Cr 3+ shows excellent persistent luminescence properties and abundant shallow traps at low temperature. This phosphor was tested at low temperature to investigate its potential as an indicator for the temperature changes of biologics.