Optical, Structural, and Chemical Characteristics of Lead‐Indium Phosphate and Lead‐Scandium Phosphate Glasses

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Abstract
Two new glass systems based on a range of lead‐indium phosphate and lead‐scandium phosphate compositions have been developed and characterized. These glasses have a relatively high index of refraction ( n = 1.75 to 1.83) in the visible region and exhibit moderate dispersion (Abbe number ∼30). The ultraviolet absorption edge occurs near 300 nm and the glasses strongly absorb in the infrared at wavelengths greater than 2800 nm. Both glass types can be prepared at relatively low temperatures (900° to 1000°C) and are easily poured down to ∼800°C because of their low melt viscosities. The glasses exhibit good chemical durability and resistance to both weathering and intense γ‐radiation. These materials have a glass transition temperature of about 430°C, a softening point of about 460°C, and thermal expansion coefficients in the range of 10.8 × 10 −6 to 12.0 × 10 −6 /°C. The structure of these phosphate glasses is shown to consist of a distribution of chains of PO 4 tetrahedra held together by bonding between the non‐bridging oxygens of the tetrahedra and the metal cations. The polyphosphate chain length distribution was determined by a liquid chromatographic technique. Potential aqueous corrosion mechanisms are discussed and some general guidelines for forming a chemically durable phosphate glass are given.

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