Phase Formation, Crystal Orientations and Epitaxy in Bi2O3/TiO2/SiO2 (/Nd2O3) Glass-Ceramics
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, Bi4-xNdxTi3O12, Bi2Si1-yTiyO5, 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, Bi4-xNdxTi3O12 and Bi2Si1-yTiyO5 are observed. A perfectly epitaxial relationship between Bi4-xNdxTi3O12 and Bi2Si1-yTiyO5 is proven by EBSD. Crystals with the compositions Bi2Si1-yTiyO5 with y=0.33, 0.5 and 0.66 are detected.