| GeO2-based novel optical glasses with high refractive index, large mid-infrared transmission, and low thermal expansion |
MinSeong Hwang1,2, Jaeyeop Chung1
, Bongki Ryu2, Wonjong Jeong2, Liyu Liu2 |
1Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Korea
2School of Material Science and Engineering, Pusan National University, Busan 46241, Korea |
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Received: December 27, 2023; Revised: April 21, 2024 Accepted: May 13, 2024. Published online: June 3, 2024. |
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| ABSTRACT |
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Glasses with a high refractive index and wide transparency in the infrared (IR) region were successfully synthesized. We prepared 20BaO–15TiO2–5Ga2O3–xTeO2-(40-x)GeO2 (x = 20–30 mol%) and xBaO–15TiO2–10Ga2O3–20TeO2-(40-x)GeO2 (x = 15–25 mol%) glasses and analyzed the relationship between their compositions and physical, thermal, and optical properties. The effects of substituting TeO2 and BaO for GeO2 on the refractive index and Abbe number are discussed based on the electronic polarizability, density of the oscillators, and resonance wavelength of the oscillators. The refractive indices increased with increasing TeO2 and BaO concentrations, owing to the increase in the electronic polarizability of oxygen and the density of the oscillators. The Abbe number decreased with increasing TeO2 concentration because the resonance wavelength of the oscillator shifted to a longer wavelength, indicating a decrease in the optical bandgap energy. In addition, we observed that the Abbe numbers were almost constant with increasing refractive index when BaO was substituted with GeO2, and this trend was similar to that of the ultraviolet absorption edge. By substituting TeO2 and BaO for GeO2, the cutoff wavelength of the IR region shifted to a longer wavelength. Furthermore, the thermal-expansion coefficient values of the glass samples developed in this study (9.45–11.58 × 10–6/K) were lower than those of commercial optical glasses. |
| Key words:
Optical glasses · Refractive index · Mid-infrared transmission |
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