High-pressure x-ray diffraction study of Ta4AlC3

Using a synchrotron radiation source and a diamond anvil cell, we measured the pressure dependence of the lattice parameters of a recently discovered phase, Ta4AlC3. This phase adopts a hexagonal structure with the space group P6(3)/mmc; at room conditions, the a and c parameters are 3.087(5) and 23.70(4) angstrom, respectively. Up to a pressure of 47 GPa, no phase transformations were observed. Like Ta2AlC, but unlike many related phases such as Ti4AlN3, Ti3SiC2, Ti3GeC2, and Zr2InC, the compressibility of Ta4AlC3 along the c and a axes are almost identical. The bulk modulus of Ta4AlC3, 261 +/- 2 GPa, is approximate to 4% greater than that of Ta2AlC. Both, however, are approximate to 37% lower than the 345 +/- 9 GPa of TaC. (c) 2006 American Institute of Physics.