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The electrical resistance of niobium and vanadium single crystals at low temperatures

University of British Columbia

An investigation into the variation of electrical resistance with temperature for high purity niobium and vanadium single crystals has been carried out. Niobium was studied over the temperature range -30°C to -146°C. It was found that in its highest purity there was little or no anomaly. At lower purities an anomaly in the region of -120°C was discovered which was attributed to oxygen or nitrogen or both changing their position on the lattice to one of higher strain energy because of changes in energy associated with the bonding between interstitials and the lattice. Hydrogen doping of niobium produced an overall increase in resistivity. A drop in the resistance curve was noted at -100°C which was thought to be due to hydrogen, being mobile and non-bonded, moving off the high strain energy sites under the influence of thermal contraction. Hydrogen embrittlement was attributed to hydrogen occupation of high strain energy-sites. Vanadium was found to have a slope change at.-170° when tested between -130°C and -196°C. No definite explanation of this is suggested. Ultrasonic testing of vanadium showed attenuation minima at -100°C and -170°C.

Text

2011-11-08

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http://hdl.handle.net/2429/38854

Metals and Materials Engineering

University of British Columbia

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