Computational Study of Structural and Electrical Properties of Doped BaTiO3 for Sensing Applications

Abstract

Barium titanate (BaTiO3) is a technologically significant material because of its ferroelectric response and high dielectric constant. BaTiO3 (BTO) is commonly used as inorganic perovskite oxides, which exhibited its significance in the field of sensors, multi-layer ceramic capacitors (MLCC), actuators, optoelectronic devices, etc. To achieve high selectivity for specific gases, ferroelectric phase transitions at specific temperatures and long-term stability are some major concerns and challenges in gas sensor design. This issue can affect the accuracy of gas detection, especially in complex environments with multiple gas components. The present research work explores the structural, electronic, and optical properties of strontium doped BTO structure for sensing application using first principles calculations. The generalized gradient approximation (GGA) with Perdew-Bruke-Emzerhof (PBE) and OTFG pseudopotential is used to perform the numerical simulation using CASTEP numerical code. The change in lattice parameters is observed after the replacement of Sr atoms with Ba atom in BTO structure due to distortion caused by impurity atom. The substitution of Sr at A-site in BTO has changed the indirect band gap of pure BTO to direct band gap along with significant variations in bandgap values for different Sr dopant atoms. The total density of states increased after doping, showing that the dopants have significantly introduced new states into the material. The partial density of states reveals that there is minor contribution of Ti 3d states which hybridized with nearby O 2p states in valence, and conduction bands. In addition, the optical properties of the materials have been calculated, and the substitution of Sr at Ba site enhances the static dielectric constant from 4.2 to 4.4. The maximum absorption for pure and doped BTO is observed in ultraviolet region (19.3-19.8 eV). High absorption coefficient in range from 4.2×105 to 5.3×105 cm-1 for pure and doped BTO has been oberved. The value of maximum peak of reflectivity for pure, one, two and three atoms Sr doped BTO structure are 8.85, 6.3, 9.02, and 8.65 respectively. At 0 Ev, the value of refractive index (n) increases from 2.5 to 2.7 after doping.