On the compression behavior of Ti2InC, (Ti0.5, Zr0.5)2InC, and M2SnC (, Nb, Hf) to quasi-hydrostatic pressures up to 50 GPa

Using a synchrotron X-ray radiation source and a diamond anvil cell we measured the dependences of the lattice parameters on quasi-hydrostatic pressure of the order of 50 GPa of the following MAX phases: Ti2InC, (Ti0.5,Zr0.5)2InC, Zr2InC and Ti2SnC, Nb2InC and Hf2InC. Like other MAX phases, the phases studied herein were all stable up to ≈50 GPa. In both series, the substitution of Ti ( r = 1.32 Å ) by the larger sized metals, Zr or Nb (with r varying between 1.34 and 1.55 Å) resulted in larger unit cell parameters and volumes. At 152±3 and 148±3 GPa, the respective bulk moduli, K o , of Ti2SnC and Ti2InC are quite comparable. Replacing Ti by Hf or Nb in Ti2SnC leads to increases in K o by 11% and 18%, respectively. Conversely, replacing half the Ti by Zr in Ti2InC leads to a 13% drop in K o ; replacing all of the Ti drops it by 16.5%. Most of these trends are reproduced in our ab initio calculations of K o . For all compositions, the compressibilities along the c -direction were greater than those along the a -direction. For the M2SnC series, the compressibilities along the c -axes were quite similar; the compressibilities along the a -axis of Ti2SnC were greater than in the Nb- or Hf-containing ternaries. The c -axis compressibilities of the In-containing compounds were almost indistinguishable. The compressibilities along the a -axes of (Ti0.5,Zr0.5)2InC and Zr2InC were also quite comparable; those of Ti2InC was less compressible.