A first principle investigation to explore the effect of Zr-site Ti doping on structural, electronic, optical, and mechanical properties of BaZrO3

Doped BaZrO₃ is well recognized as a promising material for proton conduction, particularly in solid oxide fuel cells (SOFCs) and various electrochemical applications. While this material has been thoroughly examined for proton conduction, it has not been as extensively studied for other potential applications, such as photocatalytic water splitting and solar cell devices. This investigation delves into the comprehensive assessment of structural, electronic, optical, mechanical, and thermodynamic properties in Ti-doped BaZrO₃ (BaZr_1-xTi_xO₃ where x = 0,0.25, 0.5, 0.75) through the application of Density Functional Theory (DFT) employing the Generalized Gradient Approximation (GGA) and Perdew-Burke-Ernzerhof (PBE) exchange-correlation function. After doping, all of the doped compounds undergo a phase transition from cubic to tetragonal once Ti is added to BaZrO₃. Analysis of the computed structural properties reveals a slight reduction in lattice parameters accompanied by a decrease in cell volume. The doping of Ti led to a reduction in the electronic bandgap energy of BaZrO₃. Specifically, the bandgap decreased from an initial value of 3.118 eV at x = 0, which was an indirect bandgap, to a lowest value of 1.8 eV at x = 0.5, also identified as an indirect bandgap. This bandgap reduction leads to significant changes in optical properties, enabling absorption at lower photon energies compared to pure BaZrO₃, which is beneficial for photocatalytic water splitting and solar cell applications. Mechanical properties confirmed the stability of the investigated composition through the Born stability criteria. Furthermore, thermodynamic properties across different doping concentrations revealed the highest Debye temperature at x = 0.75, indicating a higher melting point and enhanced thermal stability.