Phase formation, crystal orientations and epitaxy in Bi2O3/TiO2/SiO2(/Nd2O3) glass ceramics

Abstract

Four glasses in the Bi₂O₃/TiO₂/SiO₂ and Bi₂O₃/TiO₂/SiO₂/Nd₂O₃ systems are melted and poured into graphite moulds where they show spontaneous crystallization during cooling. The crystal phases α-Bi₂Ti₄O₁₁, Bi_4−xNd_xTi₃O₁₂, Bi₂Si_1−yTi_yO₅, TiO₂ and probably Bi₂Ti₂O₇ are shown to crystallize using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDXS) and electron backscatter diffraction (EBSD). A previously unknown miscibility of Bi₂SiO₅ and Bi₂TiO₅ is indicated. Oriented layers of monoclinic α-Bi₂Ti₄O₁₁, Bi_4−xNd_xTi₃O₁₂ and Bi₂Si_1−yTi_yO₅ are observed. A perfectly epitaxial relationship between Bi_4−xNd_xTi₃O₁₂ and Bi₂Si_1−yTi_yO₅ is proven by EBSD. Crystals with the composition Bi₂Si_1−yTi_yO₅ with y = 0.33, 0.5 and 0.66 are detected.