A Comparison of Methods for Computing the Residual Resistivity Ratio of High-Purity Niobium

Published

February 17, 2011

Author(s)

Jolene D. Splett, Dominic F. Vecchia, Loren F. Goodrich

Abstract

We compare methods for estimating the residual resistivity ratio (RRR) of high-purity niobium samples and investigate the effects of using different functional models on the final value. RRR is typically defined as the ratio of the electrical resistances measured at 273 K (the ice point) and 4.2 K (the boiling point of helium at standard atmospheric pressure). However, pure niobium is superconducting below about 9.3 K, so the low-temperature resistance is defined as the normal-state (i.e., non-superconducting state) resistance extrapolated to 4.2 K and zero magnetic field. Thus, the estimated value of RRR depends significantly on the model used for extrapolation. We examine three models for extrapolation based on temperature versus resistance, two models for extrapolation based on magnetic field versus resistance, and a new model based on the Kohler relationship that can be applied to combined temperature and field data. We also investigate the possibility of re-defining RRR so that the quantity is not dependent on extrapolating an arbitrary model.

Citation

Journal of Research (NIST JRES) -

Volume

116

NIST Pub Series

Journal of Research (NIST JRES)

Pub Type

NIST Pubs

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Keywords

cryogenic, electrical resistivity, Kohler s rule, magnetoresistance, residual resistivity ratio, superconductor

Citation

Splett, J. , Vecchia, D. and Goodrich, L. (2011), A Comparison of Methods for Computing the Residual Resistivity Ratio of High-Purity Niobium, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=906197 (Accessed October 28, 2025)