| Summary: | Herein, we report on the growth of Cr<sup>4+</sup>–Li<sub>2</sub>CaGeO<sub>4</sub> crystals by the flux growth method from the flux of LiCl, as well as on the effect of doping Li<sub>2</sub>CaGeO<sub>4</sub> with Cr<sup>4+</sup> ions on the NIR region spectral properties and crystal structure. The results quantified the occupancy of Cr<sup>4+</sup> in Ge<sup>4+</sup> sites. The emission spectrum presented broad bands in the NIR region, i.e., 1000–1500 nm excited by 980 nm, with maximum peaks at 1200 nm at room temperature caused by the transition of <sup>3</sup>T<sub>2</sub>→<sup>3</sup>A<sub>2</sub> in Cr<sup>4+</sup> ions. The lifetime decreased with the Cr<sup>4+</sup> ion doping concentration, specifically from 14.038 to 12.224 ms. The chemical composition and the valence state of chromium in Li<sub>2</sub>CaGeO<sub>4</sub> were analyzed using X-ray photoelectron spectroscopy, which showed that the chromium in Li<sub>2</sub>CaGeO<sub>4</sub> was tetravalent and no trivalent chromium was found. Therefore, the Cr<sup>4+</sup>–Li<sub>2</sub>CaGeO<sub>4</sub> crystal has a great potential and future in optical applications.
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