The preparation and properties of uranium (IV) silicate^*

Uranium (IV) orthosilicate, corresponding to the mineral coffinite, has been synthesized by a hydrothermal procedure. Preparative conditions including precipitation techniques, temperature, pH and uranium oxidation state have been investigated. USiO₄ is a blue microcrystalline compound isostructural with thorite and zircon. The infrared spectrum of USiO₄ shows an absorption maximum at 11.1 μ, characteristic of isolated SiO₄^4–tetrahedra. No evidence was found for hydroxyl substitution in the sy nthetic material. USiO₄ is stable to 1000° C. in a vacuum and to 500° C. in air.