Herein we report on a systematic investigation of the thermal expansion of select Mn+1AXn phases. The bulk dilatometric thermal expansion coefficient αdil was measured in the 25-1200 °C temperature range and the thermal expansion of more than 15 of these phases was studied by x-ray diffraction in the 25-800 °C temperature range. The coefficient of thermal expansion for the a axis αa ranged between (2.9±0.1) × 10-6 ° C-1(Nb2 AsC) and (12.9±0.1) × 10-6 ° C-1 (Cr2 GeC) while the coefficient for the c axis (αc) ranged between (6.4±0.2) × 10-6 ° C-1 (Ta2 AlC) and (17.6±0.2) × 10-6 ° C-1 (Cr 2 GeC). Weak anisotropy in the thermal expansion was seen in most phases, with the largest value of αc / αa belonging to Nb2 AsC. The Grüneisen parameters along the a and c directions were calculated from ab initio values for the elastic compliances and were relatively isotropic. A good correlation was found between the thermal expansion anisotropy and the elastic constant c13 and we conclude that the anisotropy in thermal expansion is related to the bonding between the M-A elements.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)