Physical properties of a novel boron-based ternary compound Ti2InB2

The present study aims to investigate the structural, mechanical, thermal, dynamic and optical properties of a new type and recently synthesized 212 MAX phase Ti2InB2 in comparison with other 211 MAX phases (Ti2InC, Ti2SnC and Ti2AlC). Our calculated lattice parameters show excellent agreement with the available data. The obtained elastic constants and phonon dispersion spectra confirm the mechanical and dynamical stability of the new compound. The studied MAX phases are found to be brittle in nature. In Ti2InB2, the B-B bonds exist with the larger bond population, indicating its high covalent nature, makes it stiffer than the typical 211 MAX phases, particularly, Ti2InC. Consequently, Ti2InB2 possesses high C11, C33, B, G and Y compared with Ti2InB2. The calculated hardness of the newly synthesized Ti2InB2 is the highest among all the MAX phases under consideration. Temperature and pressure dependent thermal properties are investigated through quasi-harmonic Debye model for the first time. The heat capacity of Ti2InB2 at room temperature with the inclusion of lattice and electronic contribution is higher than those of other studied 211 MAX phases. The optical reflectivity suggests that the studied MAX compounds can be promising candidates as protective coating of other materials against solar heating.