Solventless synthesis of bismuth-free and lead-free low-melting glasses

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We have recently developed the low-melting organic-inorganic hybrid silicophosphate glasses, which are prepared by mixing orthophosphoric acid with organically-modified chlorosilane at low temperature (<300℃). These glasses are capable of dissolving both rare earth ions and organic molecules, suggesting that they may be good host material candidates for optical devices. Because of the low water resistance in the atmosphere, the purpose of this study is to improve the water resistance of glasses. We proposed the hydrolytic reaction mechanism of the glasses using quantum chemical calculations. Based on this result, we concluded that the hydrolysis is assisted by acid derived from phosphoric acid and/or hydrochloric acid generated during the glass formation reaction. We also developed HCl-free reaction using orthophosphoric acid and organically-modified alkoxysilane as starting reagents to prepare the water-durable low-melting glasses.Additionally, we have also prepared an organic-inorganic hybrid phosphosilicate membrane with a lot of uniformly-dispersed phosphoric groups based on this method. Thermogravimetric and AC impedance spectroscopy have revealed that the present membrane is a potential candidate for the proton-conducting membrane.