Theoretical Investigation on Effect of Boron on Improving the Hardness of Zincblende-Aluminium Nitride and Its Mechanical, Thermal and Thermoelectric Properties

Abstract

In this paper, we present the outcome of ab-initio band structure study carried out on cubic phase ternary B_xAl_1−xN (x = 0, 0.125, 0.25, 0.5, 0.75, 0.875, 1.0) alloys in order to analyze the elastic coefficients thereby the structural, thermoelectric, electronic, thermal, mechanical, and optical properties of these alloys. With the aim of enhancing the hardness of aluminium nitride (19 GPa), the present study on the proposed combinations reveal that B_0.75Al_0.25N (40.5 GPa) and B_0.875Al_0.125N (49.5 GPa) alloys turn out to be superhard materials as their hardness surpasses 40 GPa. Further, B_0.875Al_0.125N alloy has been identified to serve as a good thermoelectric as it has a high Seebeck coefficient value of 240 µV/K and of melting temperature of 4282 K. Except for the binary compounds AlN and BN, all the other ternary alloys are predicted to be direct band gap materials. The density of states, band structure, charge density plot, various elastic moduli, Debye’s temperature, elastic wave velocity, dielectric constant, Seebeck’s coefficient and other properties of interest are discussed in this paper. The results are compared and found to agree very well with the available literature.