Bismuth silicon oxide

Bismuth silicon oxide or bismuth silicate refers to an inorganic compound of bismuth, silicon and oxygen. The bismuth silicate Bi₁₂SiO₂₀ is most commonly encountered, though others are also known. It occurs naturally as the mineral sillénite and can be produced synthetically by heating a mixture of bismuth oxide and silicon dioxide. Centimeter-sized single crystals of Bi₁₂SiO₂₀ can be grown by the Czochralski process from the molten phase. They exhibit piezoelectric, electro-optic, elasto-optic, photorefractive and photoconductive properties, and therefore have potential applications in spatial light modulators, acoustic delay lines and hologram recording equipment. Bi₁₂SiO₂₀ can be obtained as a whitish powder with band gap of approximately 3.2 eV starting from bismuth subcarbonate and silica in presence of ethyleneglycol. ²⁹Si solid-state NMR is used to prove that the Si(IV) cations are sharing oxygen atoms with the Bi(III) cations. The ²⁹Si chemical shift (δ) in Bi₁₂SiO₂₀ is −78.1 ppm. Unlike bismuth oxide, the presence of the acidic Si(IV) cations avoid the reactivity with CO₂.

Other bismuth silicates are known, such as Bi₄Si₃O₁₂, Bi₂SiO₅, and Bi₂Si₃O₉.

References