Spontaneous reduction of europium ions below 250 °C in organic–inorganic hybrid low-melting phosphite glasses

Europium-doped organic–inorganic hybrid low-melting phosphite glass was prepared from SnCl₂, Me₂SiCl₂, and H₃PO₃ (phosphonic acid) through the nonaqueous acid–base reaction process. The europium-doped glass melted at 250 °C showed fluorescence with a broad peak at 373 nm due to the 4f⁶ 5d¹ → 4f⁷ transition of Eu²⁺ ions, whereas no fluorescence from the Eu³⁺ ions was observed. Almost all of the Eu³⁺ ions incorporated into the glasses could be successfully reduced to Eu²⁺ ions at a temperature as low as 250 °C by the strong reducing power of H₃PO₃.