Structural, electronic, vibrational, optical, piezoelectric, thermal and thermoelectric properties of BCZT from first-principles calculations

Perovskite materials are well-known for their favorable piezoceramic properties and high value of Curie temperature, and have potential applications in sensors, actuators, and optoelectronic and thermoelectric devices. Based on its composition and physical parameters, such as pressure and temperature, experimentally, BCZT [Ba_0.85Ca_0.15(Zr_0.1Ti_0.9)O₃] shows different crystal structures (rhombohedral, tetragonal and orthorhombic) with multiferroic properties. We have designed these materials by comparing experimental stoichiometry and evaluated their stability by calculating the tolerance factor, formation energy, and cohesive energy. The structural, electronic and vibrational properties of BCZT are explored using the generalized gradient approximation (GGA) within the framework of density functional theory. We have also shown the variation of piezoelectric and optical properties through multiple phases using time dependent density functional theory. The electronic band gap, optical response in the visible light range, and piezoelectric, electrical, thermal, and thermoelectric properties, demonstrate excellent characteristics, making this material a promising lead-free ferroelectric candidate for various energy harvesting applications. Boltzmann transport theory is used for the calculation of the Seebeck coefficient, thermal conductivity, and electrical conductivity to estimate the power factor and figure of merit, which represents the thermal efficiency of the material. The high values at the Fermi level suggest that these materials are well-suited for future device applications.