氮氢混合气氛退火中氢对Bi4Ti3O12铁电性能的影响

采用基于密度泛函理论的第一性原理研究了在氮氢混合气氛中退火后Bi₄Ti₃O₁₂铁电性的退化机理. 分别计算了无氢、含氢模型中Ti沿c轴位移时体系总能量的变化,电子云密度分布,以及电子结构的总能态密度的变化. 结果表明含氢Bi₄Ti₃O₁₂铁电相Ti-O,Bi-O间的电子云重叠布居分布较无氢情况下变化明显,氢氧之间较强的轨道杂化使它们趋于形成共价键;晶格中氢氧键的 关键词： 氮氢混合气氛退火 铁电性 4Ti₃O₁₂')" href="#">Bi₄Ti₃O₁₂ 第一性原理

Effect of hydrogen on ferroelectric properties of Bi4Ti3O12 during forming gas annealing

Degradation of Bi₄Ti₃O₁₂ ferroelectricity during forming gas annealing is investigated by the first-principles method based on the density functional theory(DFT) the generalized gradient approximation(GGA). We calculate the variations of total energy with the displacement of Ti along the c axis, electron density and total density of states in hydrogen-free and hydrogenated models. The results show that the electron densities of Ti-O and Bi-O exhibit significant changes between the Bi₄Ti₃O₁₂ ferroelectric phases for the hydrogenated and hydrogen-free cases, and the strong hybridization between H and O is favorable to the formation of a convalent bond. The total energy of ferroelectric phase for the hydrogenated case is bigger than that of paraelectric phase because hydrogen incorporation into the lattice has a direct effect on polarization pinning by possibly forming a hydroxyl bond. This demonstrates that hydrogen introduction during forming gas annealing hinders the phase transition of the Bi₄Ti₃O₁₂ from tetragonal paraelectricity to orthogonal ferroelectricity, and electrical conductivity of Bi₄Ti₃O₁₂ is increased. This may be an important factor causing severe degradation of Bi₄Ti₃O₁₂ ferroelectricity.