研究目的
To investigate the impact of isovalent doping at the Bi sites in the fluorite-like layers of Bi4Ti3O12 on the magnitude and orientation of the spontaneous polarization vector, aiming to achieve out-of-plane polarization for device applications.
研究成果
Isovalent doping at the Bi sites in the fluorite-like layers of Bi4Ti3O12, particularly with P, effectively rotates the spontaneous polarization vector towards the out-of-plane direction, enhancing the transverse component by threefold and rotating it by 36.2°. This provides a promising approach for tailoring ferroelectric properties in BiT and similar Aurivillius compounds for advanced device applications, with P doping being most favorable under Bi-poor conditions.
研究不足
The study relies on computational methods (DFT with GGA), which may underestimate band gaps and not fully capture experimental conditions. The doping concentration (6.25%) is theoretical and may be challenging to achieve experimentally. The analysis assumes neutral charge states for impurities and does not consider dynamic effects or temperature variations. Experimental validation is not included in this paper.
1：Experimental Design and Method Selection:
The study employs first-principles density-functional theory (DFT) calculations using the plane-wave pseudopotential method with the Vienna Ab Initio Simulation Package (VASP). Generalized gradient approximation (GGA) with Perdew-Burke-Ernzerhof parametrization is used for exchange-correlation. Density-functional perturbation theory (DFPT) is applied for phonon analysis and Born effective charge calculations.
2：Sample Selection and Data Sources:
The crystal structures of pure and doped Bi4Ti3O12 are modeled with optimized lattice parameters from previous studies. Doping involves replacing Bi atoms in the fluorite-like layers with isovalent elements P, As, and Sb at a concentration of
3：25%. List of Experimental Equipment and Materials:
Computational resources include High Performance Computing facilities at the University of Connecticut and the Extreme Science and Engineering Discovery Environment (XSEDE). Software used: VASP for DFT calculations, PHONOPY for phonon computations, and FINDSYM for symmetry analysis.
4：Experimental Procedures and Operational Workflow:
Geometrical optimization of supercells (76 atoms) is performed with energy convergence tolerance of 10^-6 eV. Brillouin zone integrations use Monkhorst-Pack k-point meshes (5x5x3 for optimization, 8x8x8 for self-consistent field). Phonon modes are analyzed to understand atomic contributions to polarization. Doping effects are studied by optimizing doped structures and calculating polarization components, band gaps, and formation energies.
5：Data Analysis Methods:
Spontaneous polarization is computed from Born effective charges and ionic displacement vectors. Phonon analysis involves calculating layer-resolved dipole moments. Formation energies of doped systems are evaluated using chemical potentials. Electronic density of states is analyzed to assess band gap changes.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容
