System BaO Research Articles

The Crystal Structures of the Cubic and Tetragonal Phases of Y1Ba3Cu2O6.5 + δand Y1Ba4Cu2O7.5 + δ

The discovery of the superconducting material Y1Ba2Cu3O6+δ( “123” material) resulted in a world wide interest in the pseudo-ternary system BaO·YO·CuO. A complete study of the phases present in this system was initiated to develop a better understanding and processing of the superconducting 123 material. The crystal structures were established for two of the three ternary compounds in this system immediately after the discovery of superconductivity. One such phase was a green insulating compound Y2Ba1Cu1O5(”211”) which has the space group. The superconducting 123 compound was found to have the space group Pmmm and an ordered triple-celled perovskite structure.

PHASE EQUILIBRIA AND CRYSTAL CHEMISTRY IN THE SYSTEM Ba-Y-Cu-O*

Preliminary phase equilibria diagrams are constructed for the binary systems BaO-{1/2}Y{sub 2}O{sub 3}, BaO-CuO{sub x}, {1/2}Y{sub 2}O{sub 3}-CuO{sub x} and the ternary system BaO-{1/2}Y{sub 2}O{sub 3}-CuO{sub x}. Some melting data are used to outline an approximate primary field for the phase responsible for high temperature superconductivity in this system, Ba{sub 2}YCu{sub 3}O{sub 7-x}. A discussion is given of the crystal chemistry of the phase(s) near the composition Ba{sub 3}YCu{sub 2}O{sub x}.

Phase equilibria and crystal chemistry in the ternary system BaOTiO 2Nb 2O 5, I

A partial subsolidus phase diagram is presented of the BaOTiO 2Nb 2O 5 ternary system. Ten compounds or solid solutions in the ternary system are described. BaTi 3Nb 4O 17, BaTi 5Nb 4O 21, BaTi 7Nb 4O 25, and BaTi 9Nb 4O 29 belong to a chemically and structurally homologous series AB 2 n+1 O 4 n+5 with 3 ≦ n ≦ 6, the first member of which is isomorphous with KTi 2Ta 5O 17. They all crystallize in the orthorhombic system, space group Cmcm with essentially constant a and b parameters ( a = 6.6, b = 8.9 Å). The c parameter varies approximately linearly with composition from 21.148 Å for BaTi 3Nb 4O 17 to 34.321 Å for BaTi 9Nb 4O 29. BaTiNb 4O 13, isomorphous with KTa 5O 13, could be considered as a member of the chemical series described above but it crystallizes in the orthorhombic system, space group Pbcm with unit cell parameters a = 5.640, b = 10.738, c = 16.488 Å. A nonstoichiometric phase with a composition close to 3BaO:5TiO 2:3Nb 2O 5 crystallizes in the monoclinic system, space group P2 1 c with parameters a = 9.991, b = 9.970, c = 7.311 Å, β = 111°25′. Two other new phases are solid solutions extended on the quasi-binary join BaTiO 3Ba 5Nb 4O 15. Ba 8Ti 3Nb 4O 24 ( Ba 8 Ti 3+ 5x 4 Nb 4−x O 24 with 0 ≦ x ≦ 0.7) crystallizes with a primitive hexagonal cell with parameters a = 5.794 and c = 18.868 Å. The other phase is an incommensurate solid solution which extends from Ba 5Nb 4O 15 to the end member compound Ba 6TiNb 4O 18 (Ba 5+ x Ti x Nb 4O 15+3 x with parameters 0 ≦ x ≦ 1) crystallizing in the rhombohedral system, space group R3 m, parameters a = 5.765, c = 42.348 Å. The three solid solutions previously described, Ba 3Ti 4Nb 4O 21 (Ba 3Ti 4+5 x Nb 4−4 x O 21 with 0 ≦ x ≦ 0.3), Ba 6Ti 2Nb 8O 30 (Ba 6− x Ti 2−2 x Nb 8+2 x O 30), and BaTiO 3 (BaTi 1−5 x Nb 4 x O 3 with 0 ≦ x ≦ 0.02) were confirmed and further studied.

The system BaORuO 2Al 2O 3 with less than 50 MOL% BaO at 1300°C

The Ba-poor part of the system BaORuO 2Al 2O 3 at 1300°C in sealed Pt-capsules has been investigated. No quaternary compounds were observed in the system, but a hollandite phase Ba xRu 4O 8 (0.66<x<0.68) was formed indicating the partial reduction of Ru 4+ to Ru 3+. X-ray analysis showed BaRuO 3, Ba xRu 4O 8, RuO 2, Ba 0.75Al 11O 17.25 and Ba 1.29Al 12O 19.29 to be stable in water at 300°C and 2 kbar. BaRuO 3 is found to form soluble compounds in the presence of Al 2O 3.

Electrical characteristics of materials in the BaOFe 2O 3B 2O 3 system

Structural peculiarities, as for example segregation and crystallization in vitroceramic materials, may have a significant influence on the electrical volume resistance of materials. Interesting characteristics can be detected in the case of the system BaOFe 2O 3B 2O 3. This paper presents results showing that very different conductivity behaviours can be obtained by a suitable modification of the composition of the materials and by heat treatment.

Subsolidus phase relationships in the system BaOCaOFe 2 O 3

Abstract The phase relationships at 1100°C among the reaction products of BaO, CaO and Fe 2 O 3 were determined by the air quenching technique. Two binary solid solutions are formed, one between barium hexaferrite and a hypothetical calcium tetraferrite and another pseudobinary one adjacent to 2BaO·Fe 2 O 3 . Based on experimental results obtained by x-ray diffraction, optical microscopy and titrimetric determination of Fe +4 , the 1100°C isothermal section for the system BaOCaOFe 2 O 3 was derived.

New Materials for Hydrophone Applications- Single Crystals and Polar Glass-Ceramics

Hydrostatic piezoelectric strain coefficients dh (∼10 pC/N) and voltage coefficients gh (80–100×10-3 V m/N) on single crystals of Ba2TiSi2O8, Ba2TiGe2O8 have been measured as a function of temperature, pressure, and frequency. The values are found to be comparable to those of the state of the art piezoelectric PVDF polymers. Measurements are also made on the glass-ceramics in the compositions of BaO–TiO2–SiO2 and some isostructural materials compositions in the system BaO–TiO2–GeO2. The typical values of the piezoelectric constants of glass ceramics are almost on the order of those obtained on the respective single crystal samples. Glass-ceramics provide a promising way of achieving the larger area samples needed for various piezoelectric devices.

Alkaline durability of BaOTiO 2SiO 2 glasses

Glass fibers of TiO 2-rich composition in the system BaOTiO 2SiO 2 and those modified with other components were immersed in 2N NaOH solution at 95°C. A SrOBaOTiO 2SiO 2 glass showed much less diameter reduction than a conventional ZrO 2-containing Na 2O-SiO 2 glass (G20) especially when the ratio of the surface area of the glass specimens to solution volume was high. Fibers of SrOBaOTiO 2-SiO 2 glass and its modified version were immersed also in a Portland cement solution at 95°C. They maintained tensile strengths higher than glass G20 even after immersion for 108 h. The high alkaline durability of the TiO 2-rich glasses was interpreted in terms of the low solubility of the TiO 2 in the alkaline solution and preferential adsorption of the Sr 2+ and Ba 2+ ions on the hydrated TiO 2-rich surface layer.

The system BaOGeO 2 at high pressures and temperatures, with special reference to high-pressure transformations in BaGeO 3, BaGe 2O 5, and Ba 2Ge 5O 12

Phase relations in the system BaOGeO 2 were investigated in the pressure range 20–70 kbar in the temperature range 750–1200°C. Several new phases were identified in this system: an atmospheric phase of BaGe 2O 5 (monoclinic BaGe 2O 5 I), two high-pressure phases of BaGe 2O 5 (monoclinic BaGe 2O 5 II and tetragonal BaGe 2O 5 III), and a high-pressure phase of Ba 2Ge 5O 12. The phase boundary curve between BaGe 2O 5 II and BaGe 2O 5 III was preliminarily determined as P(kbar) = 7.7 + 0.047 T (°C). The high-pressure phases of BaGeO 3, which were previously reported by Y. Shimizu, Y. Syono, and S. Akimoto ( High Temp.-High Pressures 2, 113 (1970)) in the pressure range 15–95 kbar, were interpreted to be not single-phase materials but complicated mixtures of more than two phases in the system BaOGeO 2. X-Ray powder diffraction data for the new compounds synthesized in this study are given.

The system BaO [sbnd]SnO 2[sbnd]Fe 2O 3 with less than 50 mol% BaO at 1200°C in air, a crystallographic study

The BaO SnO 2 Fe 2O 3 system has been investigated after heating at 1200°C in air. The mol% BaO was less than 50%. In the part of the system examined five quaternary compounds were determined, BaSn 2Fe 4O 11, Ba 3SnFe 10O 20, Ba .69Sn 2.62Fe 1.38O 8, BaSn .90Fe 5.47O 11, and a compound of still unknown composition, the best approximation is BaSn 1.70Fe 2.75O 8.52. The compounds were recognized by their X-ray diffraction patterns. All X-ray powder diffraction patterns could be indexed. No indication was found for reduction of Fe 3+ to Fe 2+ at 1200°C. A solid solution of perovskite compounds was found in the system Ba 2Fe 2O 5 BaSnO 3, caused by oxidation of Fe 3+ to Fe 4+. This oxidation was observed also in the area Ba 2Fe 2O 5 BaFe 2O 4 BaSnO 3. The triangulation found in the BaO SnO 2 Fe 2O 3 system is discussed and the system is compared with the BaO TiO 2 Al 2O 3 system.

Barite as a main constituent in whiteware composition

Two series of mixes lying in the field of celsian BaO·Al 2O 3·2SiO 2 in the ternary system BaOAl 2O 3SiO 2 were investigated. These compositions were obtained using 35 to 60% barite together with either clay and feldspar or clay, feldspar and quartz. The amount of unreacted BaSO 4 was determined by chemical means. The effect of barite addition on physical properties, reversible linear thermal expansion and modulus of rupture of the produced bodies was verified. Results showed that 35 to 40% barite was consumed in the reaction with other constituents forming celsian BaO·Al 2O 3·2SiO 2 and sanbornite BaO·2SiO 2. Higher additions of barite left unreacted BaSO 4 as a constituent of the fired product. Unreacted barite increased the bulk density, 2.2–2.9 g/cm 3, raised the linear thermal expansion coefficient, 4.2–8.5 10 −6/°C, between 20–1000°C and lowered the modulus of rupture, 450-180 kg/cm 2.

The system BaOSnO 2Fe 2O 3 with less than 50 mole% BaO at 1200°C in air, a crystallographic study : M. C. Cadée and D. J. W. Ijdo, Section of Solid State Chemistry, Gorlaeus Laboratories, Leiden State University, P.O. Box 9502, 2300 RA Leiden, The Netherlands

The system BaOSnO 2Fe 2O 3 with less than 50 mole% BaO at 1200°C in air, a crystallographic study : M. C. Cadée and D. J. W. Ijdo, Section of Solid State Chemistry, Gorlaeus Laboratories, Leiden State University, P.O. Box 9502, 2300 RA Leiden, The Netherlands

Subsolidus equilibria in the system BaO.TiO 2.Al 2O 3

The subsolidus phase equilibrium relations in the system BaO.TiO 2.Al 2O 3 have been investigated using conventional solid state reaction techniques and X-ray powder diffraction. The existence of three known ternary compounds, BaTi 5Al 2O 14, BaTiAl 6O 12, and Ba 3TiAl 10O 20, was confirmed and their stability relations were studied. Various tie-lines existing between the ternary compounds and the binary titanates and aluminates of barium were established and a subsolidus phase diagram showing the phase assemblages compatible at 1200°C is presented.

Compounds in the system BaO  In 2O 3

The occurrence of compounds in the system BaOIn 2O 3 has been investigated. In addition to the already known compounds BaIn 2O 4 and Ba 4In 6O 13, three new compounds were found: Ba 2In 2O 5, Ba 3In 2O 6 and Ba 5In 2O 8. Ba 2In 2O 5 has a simple, perovskite-like X-ray diagram, which however, could not be indexed. Ba 3In 2O 6 and Ba 5In 2O 8 have tetragonal body-centered unit cells with a = 4.1913 A ̊ , c = 21.6693 A ̊ and a = 4.1742 A ̊ , c = 29.431 A ̊ respectively. Ba 3In 2O 6 reacts with most air to form a hydrogarnet: Ba 3In 2(OH) 12.

Subsolidus phase relationships in the system BaOCaOFe 2 O 3

The phase relationships at 1100°C among the reaction products of BaO, CaO and Fe 2O 3 were determined by the air quenching technique. Two binary solid solutions are formed, one between barium hexaferrite and a hypothetical calcium tetraferrite and another pseudobinary one adjacent to 2BaO·Fe 2O 3. Based on experimental results obtained by x-ray diffraction, optical microscopy and titrimetric determination of Fe +4, the 1100°C isothermal section for the system BaOCaOFe 2O 3 was derived.

EPR of Mn2+, Fe3+, and Cu2+ in glasses of the systems BaO–B2O3–Al2O3 and CaO–B2O3–Al2O3

An electron paramagnetic resonance study was made of Mn2+, Fe3+, and Cu2+ doped into the glass systems BaO–B2O3–Al2O3 and CaO–B2O3–Al2O3. The spectra of the manganese doped samples exhibited a barely resolved Mn2+ hyperfine pattern at g=2 and in some cases low field lines at g∼3 and g∼5. The concentration dependence of these low field lines is interpreted in terms of the lattice distortion produced by the very large barium and calcium ions and the resulting large zero field (D term) splitting. The 0.1% Mn samples produced better resolved hyperfine patterns than the 1% samples. The spectra of iron and copper doped glasses were also strongly concentration dependent. The results are discussed in terms of the glassy regions of the phase diagram.

Preparation and characterization of new ternary compounds in the system BaOTiO 2Al 2O 3

Three new ternary compounds, BaTi 5Al 2O 14, BaTiAl 6O 12, and Ba 3TiAl 10O 20 have been identified in the system BaOTiO 2Al 2O 3 and were characterized by X-ray powder diffraction. BaTi 5Al 2O 14 has a tetragonal unit-cell with a = 7.025 Å, c = 10.156 Å, and Z = 2. The compound melts incongruently at 1500°C. BaTiAl 6O 12 also has a tetragonal unit-cell with a = 10.07 Å, c = 9.107 Å, and Z = 4. The compound melts incongruently at 1560°C. Ba 3TiAl 10O 20 has an orthorhombic unit-cell with a = 14.854 Å, b = 11.356 Å, c = 4.986 Å, and Z = 2. The compound dissociates in the solid state at 1440°C to yield BaTiAl 6O 12 and BaAl 2O 4.

Preparation and characterization of new ternary compounds in the system BaOTiO 2Al 2O 3: J. P. Guha and D. Kolar. Institute Jožef Stefan, University of Ljubljana, Ljubljana. And B. Volavšek. College of Chemistry, Maribor, Yugoslavia

Preparation and characterization of new ternary compounds in the system BaOTiO 2Al 2O 3: J. P. Guha and D. Kolar. Institute Jožef Stefan, University of Ljubljana, Ljubljana. And B. Volavšek. College of Chemistry, Maribor, Yugoslavia

Compounds in the system BaOY 2O 3

Starting with BaO and Y 2O 3, four compounds are found in the BaOY 2O 3 system. At high temperatures (above 1200°C) two compounds mentioned in literature are found: Ba 3Y 4O 9 and BaY 2O 4. Heating the oxidic mixtures at 900°C results in the formation of a new compound Ba 2Y 2O 5. This compound is transformed at 1000°C into another new compound: Ba 4Y 2O 7. X-ray data of the four compounds are given in detail.

Compounds in the system BaOSc 2O 3

The occurrence of compounds in the system BaO-Sc 2O 3 has been investigated. Apart from the already known compounds Ba 3Sc 4O 9 and BaSc 2O 4, tetragonal Ba 2Sc 2O 5 has been found. This phase is the only compound formed at low temperature (1000°C). At higher temperatures Ba 2Sc 2O 5 is transformed into the other stable compounds, whereas remaining Ba 2Sc 2O 5 may dissolve excess BaO, changing the unit cell constants. A tetragonal compound Ba 6Sc 6O 15, was also observed.