Near-infrared luminescence from Li₂ZnGeO₄:Ln³⁺ (Ln = Er, Tm, Ho)

In this work, ceramic compounds Li₂ZnGeO₄:Ln³⁺ (Ln = Er, Tm, Ho), belonging to the family of germanate olivines, were studied. The structural properties were examined using X-ray diffraction, scanning electron microscopy, IR and Raman spectroscopy. Near-infrared luminescence spectra showed that the bands located in the spectral range of 1400-2100 nm were due to the electronic transitions of lanthanide ions: ⁴I_13/2 → ⁴I_15/2 (Er³⁺), ³H₄ → ³F₄ and ³F₄ → ³H₆ (Tm³⁺), and ⁵I₇ → ⁵I₈ (Ho³⁺). Decay curve analysis indicated that the near-infrared luminescence from the excited states of lanthanide ions in Li₂ZnGeO₄ was relatively long-lived. The results suggest that germanate olivines Li₂ZnGeO₄:Ln³⁺ (Ln = Er, Tm, Ho) are promising inorganic phosphors and can be successfully used as ceramic sources emitting near-infrared radiation.