Structure-density relationship for crystals and glasses in the Rb2O-B2O3-SiO2 system

The paper presents new data on the crystal structure behaviour of the Rb bo roleucite phase under Si4+-->B3+ substitution and on the density of glasses and crystals. Polycrystalline samples were prepared by glass crystallisati on. The crystal structures of the Rb boroleucite, RbBSi2O6 and two of its s ilica rich solid solutions, Rb-0.96(B0.77Si2.18)(2.95)O-6 and Rb-0.92(Ba0.4 6Si2.42)(2.88)O-6, have been determined by the Rietveld method. They are is ostructural with boroleucite, KBSi2O6 (cubic system; I3d). When B3+ is subs tituted for Si4+, vacancies are formed at the B and Rb sites in the structu re of the resulting silica Rb leucite solid solutions.