Phase Equilibria in the System BaTiO₃‐SiO₂

Abstract

The system BaTiOrSiOz is characterized by two congruently melting compounds and a compound having a subsolidus stability maximum. A barium analogue of the mineral sphene, BaTiSiOa, was shown to melt congruently at 1400OC. and BaTiSizO7 melted congruently at 125OOC. The gem mineral benitoite (BaTiSi30s) was synthesized hydrothermally and was shown to decompose below the solidus to form BaTiSi207 and SiOz when heated above 965OC. hydrothermally or above 105OOC. dry. Three eutectics in the system were determined: at 1245OC. and 70 mole % SiO,, at 1246OC. and 63% SiO2, and at 1260OC. and about 29% Si02. Glasses with high refractive indices were obtained over a limited range of compositions. The cubichexagonal transition temperature in barium titanate was raised sharply by small additions of silica. The maximum inversion temperature observed was 1575OC. and must have been due to limited solid solution of SiOn in BaTiOa.

In-situ size control and structural characterization of barium titanate nanocrystal prepared by crystallization of amorphous phase

“…Thermal and wide-angle XRD measurements were reported in the literature to determine the kinetics of crystallization [14,15]. It was suggested by Kim et al that the change of the relaxation time of the ac conduction against temperature was due to an atomic mobility change during crystallization of the xBaTiO 3 -(1Àx)SiO 2 glass [14].…”

Shape of the liquidus surface as a criterion of stable glass formation

“…H ence it is necessary to explain why , alo ng the BaO·Ti02-Si02 join, glasses are formed only in the llarrow composition range of 40 to 50 mole percent of SiOz, and in particular, wh y , as Si02 is increased slightly to 52.5 mole percent or more, a m ixture of glass and crystals is obtained. The phase diagram of the B aO· Ti02-i02 sys tem [14] s uggesLs a simple explanation . The portion of th e liquidus cur ve for the Si02-rich region of the system i extr em ely steep ; t herefore, it is dif-:acult to keep the primary phase, Si02, in solution as t he melt is cooled .…”

Kirkendall porosity in barium titanate–strontium titanate diffusion couple

“…1) contain the {1 1 1} double-twin lamellae [15,19]. Although both regions are located in the initially BaTiO 3 side, in contrast to region (iii) represented by refined grains and polytitantes, region (iv) containing abnormally grown BaTiO 3 grains dispersed in a fine-grain matrix is typical [18] of TiO 2 -excess powder sintered at temperatures below the BaTiO 3 -SiO 2 eutectic at 1260 8C [20].…”