Thermal properties of Ti3SiC2

The thermal properties of polycrystalline Ti3SiC2 in the 25 degrees C-1000 degrees C temperature range determined by Rietveld refinement of high tempe rature neutron diffraction data, show that at all temperatures, the amplitu des of vibration of the Si atoms are higher than those of the Ti and C atom s. Up to 700 degrees C, the vibrations of the Si atoms are quite isotropic but the vibrations of the other atoms are greater along the c-than along th e a-axis. The amplitudes of vibration of the Ti atoms adjacent to the Si at oms are higher and more anisotropic than for the other Ti atom sandwiched b etween the C-layers. Good agreement is obtained between the bulk thermal ex pansion coefficients measured by dilatometry, 9.1(+/-0.2) x 10(-6)degrees C -1, and the values from the neutron diffraction results, 8.9(+/-0.1) x 10(- 6)degrees C-1. The thermal expansion coefficients along the a-and c-axes ar e, respectively, 8.6(+/-0.1) x 10(-6)degrees C-1 and 9.7(+/-0.1) x 10(-6)de grees C-1. The heat capacity is 110 J/mol K at ambient temperatures and ext rapolates to approximate to 155 J/mol K at 1200 degrees C. The room tempera ture thermal conductivity is 37 W/m K and decreases linearly to 32 W/m K at 1200 degrees C. The thermal conductivity is dominated by delocalized elect rons. (C) 1999 Elsevier Science Ltd. All rights reserved.