Mechanical, Thermophysical, and Ultrasonic Properties of Thermoelectric HfX2 (X = S, Se) Compounds

Abstract

In the present study, ultrasonic and thermophysical behaviour of thermoelectric hexagonal structured HfX2 (X = S, Se) compounds have been analysed by the theoretical evaluation of second and third order elastic constants (SOECs and TOECs) using many body interaction potential model. The computed SOECs have been used to determine the temperature dependent specific heat, thermal energy density, elastic coupling constants, Gruneisen parameters, ultrasonic velocities, Debye average velocity, ultrasonic attenuation, and thermal relaxation time. We have observed that the temperature dependent ultrasonic attenuation and thermal relaxation time for HfX2 are mainly affected by thermal conductivity. The elastic properties of the material are compared with existing data in literature for the validation of the work. The obtained values of elastic stiffness are found very large in comparison to that of other material from transition metal dichalcogenides of group IVB indicating better mechanical properties than the same group materials. Calculated elastic, thermal, and ultrasonic properties are correlated for better characterization of the materials which are useful for thermoelectric and energy transport applications.