Low temperature heat capacities of Ti3Al1.1C1.8, Ti4AlN3, and Ti3SiC2

For the binary Ti-Al system, an ordering transformation in Ti3Al has been shown to result in a significant lowering of the electronic heat-capacity coefficient, gamma, by removing electrons from conducting states. When gamma is normalized to a per Ti atom basis, the same tendency is found in low temperature calorimetric studies of the conducting ternary carbides Ti3Al1.1C1.8, Ti4AlN3, and Ti3SiC2 reported herein. As a consequence of C- or N-induced covalent-like bond formation, the Debye temperatures in these ternaries are in excess of 700 K. (C) 1999 American Institute of Physics. [S0021-8979(99)00819-1].