We determine the optical bandgap energy and the Urbach energy in trivalent erbium (Er³⁺) doped oxyfluoro-germanate glass-ceramics from the ultraviolet-visible absorption spectra. The glass-ceramics are produced by subjecting the as-prepared glass to heat treatment at various temperatures above T_g (494 °C) for 1 hour. The calorimetric measurements show that the nanocrystals formed during heating are stable and the composition of the remaining glass matrix remains unchanged. It is found that both the density and the bandgap energy of the glass ceramics vary non-linearly with increasing heat-treatment temperature. This non-linear trend accords with that for the upconversion luminescence of these materials. Furthermore, the indirectly allowed transition in bandgap is observed in all the studied glass ceramics. An exponential dependence of absorption coefficient on the photon energy is observed, indicating that the Urbach rule is obeyed. The results derived from this study will be potentially useful for designing the rare earth ion doped glass-ceramics with a strong luminescence effect.

我们从紫外可见吸收光谱确定三价（Er ³⁺）掺杂的氟代锗酸盐玻璃陶瓷中的光学带隙能量和Urbach能量。通过使所制备的玻璃在高于T _g的各种温度下进行热处理来制备玻璃陶瓷。（494°C）1小时。量热法测量表明，在加热期间形成的纳米晶体是稳定的，并且剩余玻璃基质的组成保持不变。已发现，随着热处理温度的升高，玻璃陶瓷的密度和带隙能量均呈非线性变化。这种非线性趋势与这些材料的上转换发光的趋势一致。此外，在所有研究的玻璃陶瓷中均观察到带隙的间接允许跃迁。观察到吸收系数对光子能量的指数依赖性，这表明遵守了乌尔巴赫法则。这项研究得出的结果对于设计具有强发光效应的稀土离子掺杂的玻璃陶瓷可能是有用的。