Thermal and electrical properties of Nb₂AlC, (Ti, Nb)₂AlC and Ti₂AlC

Author： Barsoum M. Salama I. El-Raghy T. Golczewski J. Seifert H. Aldinger F. Porter W. Wang H.

ISSN： 1543-1940

Source： Metallurgical and Materials Transactions A, Vol.33, Iss.9, 2002-09, pp. : 2775-2779

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Abstract

The heat capacities, thermal-expansion coefficients, thermal and electrical conductivities of Nb₂AlC (actual Nb:Al:C mole fractions: 0.525±0.005, 0.240±0.002, and 0.235±0.005, respectively), Ti₂AlC and (Ti, Nb)₂AlC (actual Ti:Nb:Al:C mole fractions: 0.244±0.005, 0.273±0.005, 0.240±0.003, and 0.244±0.005, respectively) were measured as a function of temperature. These ternaries are good electrical conductors, with a resistivity that increases linearly with increasing temperatures. The resistivity of (Ti, Nb)₂AlC is higher than the other members, indicating a solid-solution scattering effect. The thermal-expansion coefficients, in the 25 °C to 1000 °C temperature range, are comparable and fall in the narrow range of 8.7 to 8.9 × 10⁻⁶ K⁻¹, with that of the solid solution being the highest. They are all good conductors of heat, with thermal conductivities in the range between 15 to 45 W/m K at room temperature. The electronic component of the thermal conductivity is the dominant mechanism at all temperatures for Nb₂AlC and (Ti, Nb)₂AlC. The conductivity of Ti₂AlC, on the other hand, is high because the phonon contribution to the conductivity is nonnegligible.