A study of the phase and glass forming diagrams of the BaO-Bi2O3-B2O3 system

The phase diagram of the binary Bi2O3-B2O3 System has been corrected. The eutectic composition has been determined as 48.5Bi(2)O(3).51.5B(2)O(3), between BiBO3 and Bi3B5O12, with melting point 665 degrees C. BiBO3 melts congruently at 685 +/- 5 degrees C. Six phase diagrams of the pseudo-binary Bi4B2O9-BaBi2B2O7, BiBO3-BaBi10B6O25, BaBi2B4O10-BaBi10B6O25, BaBi2B4O10- BaBi2B2O7, BaB2O4-BaBi2B2O7, BiBO3-BaB2O4 systems have been constructed, and eight pseudo-binary eutectic compositions have been revealed. Two new crystalline ternary compounds, BaBi2B2O7 and BaBi10B6O25, have been revealed at the crystallisation of the same glass compositions. Both compounds melted congruently: BaBi2B2O7 at 725 +/- 5 degrees C, and BaBi10B6O25 at 690 +/- 5 degrees C. Single crystals of the new compound BaBi10B6O25 were grown from the melt by stoichiometric composition cooling. X-ray characteristics of both compounds were determined. BaBi2B2O7 has an orthorhombic cell with lattice parameters a=11.818 angstrom, b=8.753 angstrom, c=7.146 angstrom, cell volume V=739.203 angstrom(3), Z=4. BaBi10B6O25 has orthorhombic crystal symmetry and lattice constants a=6.434 angstrom, b=11.763 angstrom, c=29.998 angstrom, V=2270.34 angstrom(3), Z=8. The influence of various methods of melt casting on glass forming ability in the ternary BaO-Bi2O3-B2O3 system is investigated. The expanded glass formation area changes from stable glass forming barium borates and binary bismuth borates up to barium bismuthates. All stoichiometric compositions are in the area of stable glasses.