Phase Equilibria in the System BaO–TiO₂

Abstract

The system BaO-Ti02 was investigated using quenching, strip-furnace, and thermal techniques. Five compounds were found to exist in the system: BazTi04, BaTiOa, BaTizOa, BaTi307, and BaTi409. Of these, only barium metatitanate (BaTi03) melts congruently (at 1618°C.). The dititanate melts incongruently at 1322°C. to yield BaTiOr and liquid ; the trititanate melts at 1357OC. to yield BaTi409 and liquid; the tetratitanate melts to TiOz and liquid at 1428OC. The nature of melting of the orthotitanate could not be determined accurately because of the high temperature involved and the rapid reaction with platinum. The two eutectics in the system occur between BazTi04 and BaTiOs at 1563°C. and between BaTizOs and BaTi307 at 1317OC. The temperature of the cubic-hexagonal transition in barium metatitanate was determined as 146OOC. and the transition has been shown to be reversible. The transition temperature is raised sharply by the addition of a small percentage of TiOz although the extent of solid solution is quite limited. Some applications to the manufacture of titanate bodies and to the growth of single crystals of barium metatitanate are discussed.

Dielectric Properties of Poly- and Single-Crystalline BaTi<SUB>2</SUB>O<SUB>5</SUB>

“…[1][2][3][4][5] Our group 6,7) and Akishige et al 8) independently synthesized single-crystalline BT 2 and reported the significant ferroelectricity only in the bdirection. Since BT 2 can be easily decomposed into BaTiO 3 (BT) and Ba 6 Ti 17 O 40 (B 6 T 17 ) above 1500 K, large-scale crystalline BT 2 can be hardly prepared.…”

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

“…This morphology may be attributed to the presence of a liquid phase during sintering 390 , ascribed to the eutectic point that Ba 6 Ti 17 O 40 forms with BT at ~ 1320 °C. [387][388][389] Liquid phase sintering could explain the presence of intragranular porosity in coarse grains, as it was reported that intragranular porosity requires fast mobility of grain boundaries above the pore shrinkage rate. 391 A detailed sintering study would be required to corroborate the aforementioned hypothesis, which is out of the scope of this work.…”

Phase Diagramm, Cristallization Behavior and Ferroelectric Properties of Stoichiometric Glass Ceramics in the BaO-TiO2-B2O3 System

“…~450°C in the binary B 2 O 3 -TiO 2 system [Pavlikov et al, 1976]; compositions content 30÷35 mol% BaO around eutectic area e 7 (~31.5 mol% BaO) with m.p. 1317°C in the binary BaO-TiO 2 system [Rase & Roy, 1955;O'Bryan &Thomson, 1974], which include BaTi 2 O 5 composition. Area of glass formation from both these areas moves to eutectic areas e 1 (16,5 mol% BaO) with m.p.…”

“…On the DTA curve of the 33.3BaO · 66.67TiO 2 (mol%) glass composition strongly expressed exothermic effect with maximum at 740ºС and endothermic effect with minimum at 1320ºС were observed, which show the crystallization and melting of one crystalline phase (Fig.3 , curve 5). According to [Rase & Roy, 1955] the 33.3BaO · 66.67TiO 2 (mol%) composition is melted incongruently at 1310ºС with melt and BaTiO 3 formation.…”

“…Binary BaO-TiO 2 and BaO-B 2 O 3 systems are investigated rather in detail by various authors. The following eight binary barium titanates known in the BaO-TiO 2 system are: Ba 2 TiO 4 (2BaT), BaTiO 3 (BaT), BaTi 2 O 5 (Ba2T), Ba 6 Ti 17 O 40 (6Ba17T), Ba 4 Ti 13 O 30 (4Ba13T), BaTi 4 O 9 (Ba4T), Ba 2 Ti 9 O 20 (2Ba9T) and BaTi 5 O 11 (Ba5T) [Rase & Roy, 1955;O'Bryan & Thomson, 1974]. Levin with co-authors have studied the BaO-B 2 O 3 system and constructed its melting diagram.…”