Measurement of the thermal-expansion coefficient of nickel from 300 to 1000 K and determination of the power-law constants near the Curie temperature

Abstract

A fused-quartz dilatometer was used to measure the thermal-expansion coefficient $\ensuremath{\alpha}$ of nickel between 300 and 1000 K. Measurements on National Bureau of Standards certified copper and tungsten standards with the dilatometer established the uncertainty in the $\ensuremath{\alpha}$ measurements on nickel as \ifmmode\pm\else\textpm\fi{} 0.8% (\ifmmode\pm\else\textpm\fi{}0.10 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}6}$ ${\mathrm{K}}^{\ensuremath{-}1}$), except within \ifmmode\pm\else\textpm\fi{} 2 K of the Curie temperature ${T}_{C}$ where the uncertainty was about \ifmmode\pm\else\textpm\fi{} 1.6%. Results of 38 investigations of the expansion of nickel reported in the literature were analyzed critically, resulting in a compilation of $\ensuremath{\alpha}$ of nickel from 0 to 1500 K. Theories of thermal expansion were employed to separate $\ensuremath{\alpha}$ into its paramagnetic ${\ensuremath{\alpha}}_{p}$ and magnetic ${\ensuremath{\alpha}}_{m}$ components. The calculated values of ${\ensuremath{\alpha}}_{m}$ near ${T}_{C}$ were fitted to the power-law equation, ${\ensuremath{\alpha}}_{m}=A({t}^{\ensuremath{-}a}\ensuremath{-}1){a}^{\ensuremath{-}1}+B$, that describes critical phenomena near the critical temperature [$t=(T\ensuremath{-}{T}_{C}){T}_{C}^{\ensuremath{-}1}$]. It was demonstrated that the critical exponents above and below ${T}_{C}$, $a$ and ${a}^{\ensuremath{'}}$, respectively, are the same as those derived from specific-heat measurements and that $a={a}^{\ensuremath{'}}=\ensuremath{-}0.093(\ifmmode\pm\else\textpm\fi{}0.010)$ in agreement with scaling laws of critical phenomena.