Phase relationship, vaporization, and thermodynamic properties of the lanthanum--boron system

Journal Article · Thu Jan 12 00:00:00 EST 1978 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100490a014· OSTI ID:5253638

Storms, E; Mueller, B

The La-B system was studied between LaB/sub 4.24/ and LaB/sub 29.2/, and between 1400 and 2100 K to determine the phase relationship, the chemical activity of the components, the vaporization rate, and the vapor composition. A blue colored phase near LaB/sub 9/ was found to exist between purple colored LaB/sub 6/ and elemental boron. Diffusion is so much slower than vaporization that large composition differences can exist between the surface and the interior which, nevertheless, produce a steady state loss rate from freely vaporizing material. The flux at 1700 K is 6 x 10/sup -10/ g/cm/sup 2/s for LaB/sub 4/+LaB/sub 6/ and 7 x 10/sup -11/ g/cm/sup 2/s for LaB/sub 6/ + LaB/sub 9/. There is an activation energy which lowers the vaporization rate of boron from LaB/sub 6/. Freely vaporizing material will have a steady state surface composition between LaB/sub 6.04/ and LaB/sub 6.07/, depending on temperature, purity, and interior composition. The free energy of formation of LaB/sub 6/ is (0.07lT - 351)kJ/mol between 1700 and 2100 K.

• Research Organization: Los Alamos Scientific Lab., NM
• OSTI ID: 5253638
• Journal Information: J. Phys. Chem.; (United States), Vol. 82:1
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BORON
EVAPORATION
PHASE STUDIES
THERMODYNAMIC PROPERTIES
LANTHANUM
VERY HIGH TEMPERATURE
ELEMENTS
METALS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RARE EARTHS
SEMIMETALS
400201* - Chemical & Physicochemical Properties