Strontium metaphosphate Sr(PO3)2 – optical grade 99.99%
The combination of sodium and strontium polyphosphate forms a low-melting glass with a high coefficient of thermal expansion. The melting point of the glass increases with Strontium content. This glass makes seals with low melting metals like aluminium (melting point 650 °C). Normal borosilicate glasses soften above the melting point of aluminium. This mixture is prepared by heating a mixture of diammonium phosphate, sodium carbonate, and Strontium carbonate.