Preparation and investigation of high purity Ge–Te–AgI glasses for optical application

• The high-purity GeTe4–AgI glasses were prepared.
• Glass samples are characterized by low content of impurities.
• The value of bulk absorption coefficient at 10.6 μm was 0.7 dB/m.

The method for the preparation of high purity Ge–Te–AgI glasses with low content of the limiting impurities has been developed. The method includes the synthesis of GeTe4 glass using chemical distillation purification, loading AgI and GeTe4 into silica glass reactor by evaporation in all-sealed glass vacuumed system, melting the (GeTe4)100 − x(AgI)x (x = 0–20) glass into muffle rocking furnace at 850 °С, quenching the glass in water with subsequent annealing and cooling.The prepared glass samples were investigated by energy-dispersive X-ray microanalysis, DSC, FTIR-spectroscopy, Raman spectroscopy, and laser calorimetry.The high purity (GeTe4)100 − x(AgI)x (x = 0–20) glass samples are characterized by good transparency in the spectral range of 2–20 μm, glass transition temperature of 140–160 °С, Tc − Tg difference of more than 100 °С, and a very low content of the limiting impurities. Some glass compositions with AgI content between 10 and 20 at.% manifest a good thermal stability against crystallization.