Michel Veronica F, Esswein Tobias, Spaldin Nicola A
Materials Theory, Department of Materials, ETH Zürich Wolfgang-Pauli-Strasse 27 8093 Zürich Switzerland
J Mater Chem C Mater. 2021 Jun 22;9(27):8640-8649. doi: 10.1039/d1tc01868j. eCollection 2021 Jul 15.
We explore the interplay between ferroelectricity and metallicity, which are generally considered to be contra-indicated properties, in the prototypical ferroelectric barium titanate, BaTiO. Using first-principles density functional theory, we calculate the effects of electron and hole doping, first by introducing a hypothetical background charge, and second through the introduction of explicit impurities (La, Nb and V for electron doping, and K, Al and Sc for hole doping). We find that, apart from a surprising increase in polarization at small hole concentrations, both charge-carrier types decrease the tendency towards ferroelectricity, with the strength of the polarization suppression, which is different for electrons and holes, determined by the detailed structure of the conduction and valence bands. Doping with impurity atoms increases the complexity and allows us to identify three factors that influence the ferroelectricity: structural effects arising largely from the size of the impurity ion, electronic effects from the introduction of charge carriers, and changes in unit-cell volume and shape. A competing balance between these contributions can result in an increase or decrease in ferroelectricity with doping.
我们研究了铁电性与金属性之间的相互作用，这两种性质通常被认为是相互矛盾的，我们以典型的铁电体钛酸钡（BaTiO₃）为例进行研究。利用第一性原理密度泛函理论，我们首先通过引入假想的背景电荷，其次通过引入明确的杂质（电子掺杂用La、Nb和V，空穴掺杂用K、Al和Sc）来计算电子和空穴掺杂的影响。我们发现，除了在小空穴浓度下极化出现惊人的增加外，两种载流子类型都会降低铁电倾向，电子和空穴的极化抑制强度不同，这由导带和价带的详细结构决定。用杂质原子掺杂增加了复杂性，使我们能够确定影响铁电性的三个因素：主要由杂质离子大小引起的结构效应、引入载流子产生的电子效应以及晶胞体积和形状的变化。这些贡献之间的竞争平衡可能导致掺杂时铁电性增加或降低。
