MoAlB is the first and, so far, the only transition-metal boride that forms alumina when heated in air and is thus potentially useful for high-temperature applications. Herein, the thermal stability in argon and vacuum atmospheres and the thermodynamic parameters of bulk polycrystalline MoAlB were investigated experimentally. At temperatures above 1708 K, in vacuum and inert atmospheres, this compound incongruently melts into the binary MoB and liquid aluminum metal as confirmed by differential thermal analysis, quenching experiments, x-ray diffraction, and scanning electron microscopy. Making use of that information together with heat-capacity measurements in the 4-1000-K temperature range-successfully modeled as the sum of lattice, electronic, and dilation contributions-the standard enthalpy, entropy, and free energy of formation are computed and reported for the full temperature range. The standard enthalpy of formation of MoAlB at 298 K was found to be −132 ± 3.2 kJ/mol. Lastly, the thermal conductivity values are computed and modeled using a variation of the Slack model in the 300-1600-K temperature range.

T2-Al2MgC2 was synthesized from the elements in a Mg-Al melt at 1000°C using sealed Ta crucibles. Single crystals of T2-Al2MgC2 were extracted by evaporating the Mg-Al matrix. The crystal structure of T2-Al2MgC2 was refined for the first time on the basis of single-crystal X-ray diffraction. The crystal is trigonal (space group P-3m1, Z=1) with lattice parameters of a=3.3767(11) Å, c=5.807(2) Å and V=57.34(5) Å 3. Based on the refined crystal structure, DFT calculations were conducted to evaluate the thermodynamic properties and the electronic structure of the phase. The heat of formation of T2-Al2MgC2 was calculated to be-23.6 kJ/moles of atoms at 298K. The heat capacity of T2-Al2MgC2 was measured by DSC from 300 to 871K and calculated by DFT from 0 to 1000K. Based on the calculated heat capacity, the entropy of formation of the phase at 298K was determined to be 70.0 J/mol/K. The band structure and the electronic density of state of T2-Al2MgC2 was calculated leading to an indirect band gap value of 1.73 eV.