Post density functional theoretical studies of highly polar semiconductive Pb(Ti1−xNix)O

Gaoyang Gou

¹

,

Joseph W. Bennett

²

,

Hiroyuki Takenaka

³

et al.

Abstract

We use a combination of conventional density functional theory (DFT) and post-DFT methods, including the local density approximation plus Hubbard U (LDA+U ), PBE0, and self-consistent GW to study the electronic properties of Ni-substituted PbTiO 3 (Ni-PTO) solid solutions. We find that LDA calculations yield unreasonable band structures, especially for Ni-PTO solid solutions that contain an uninterrupted NiO 2 layer. Accurate treatment of localized states in transition-metal oxides like Ni-PTO requires post-DFT methods. B-site Ni/Ti cation ordering is also investigated.The B-site cation arrangement alters the bonding between Ni and O, and therefore strongly affects the band gap (E g ) of Ni-PTO. We predict that Ni-PTO solid solutions should have a direct band gap in the visible light energy range, with polarization similar to the parent PbTiO 3 . This combination of properties make Ni-PTO solid solutions promising candidate materials for solar energy conversion devices.

Effect of thickness on dielectric, ferroelectric, and optical properties of Ni substituted Pb(Zr0.2Ti0.8)O3 thin films

“…1,[8][9][10]18 The decrease of band gap by Ni-substitution in different materials has also been reported theoretically and experimentally by other research groups. [8][9][10]53,54 Here, the effect of thickness on E g is our central focus. A decrease was observed in direct-E g values from 4 eV to 3.4 eV and indirect-E g values from 3.5 eV to 2.9 eV as the thickness of the films increases from 5 nm to 400 nm.…”

“…4 Theoretically, it has been proposed that metallic defects, substitutions of transition metal ions can reduce the band gap of ferroelectric materials, which is a basic requirement for their applications as photovoltaic devices for complete solar spectrum. [8][9][10] The polarization of FE materials can also be tuned via strain-polarization coupling. Stained ferroelectric films exhibit polarization and dielectric values superior to the corresponding bulk counterpart.…”

Экспериментальное и теоретическое исследование примесных центров Ni в Ba-=SUB=-0.8-=/SUB=-Sr-=SUB=-0.2-=/SUB=-TiO-=SUB=-3-=/SUB=-

“…Недавние теоретические работы показали, что заме-щение Ti в PbTiO 3 примесью с электронной конфи-гурацией d 8 (Ni, Pd, Pt), компенсированной вакансией кислорода, позволяет уменьшить ширину запрещенной зоны этого материала [6,7]. Проведенные нами экспе-риментальные исследования SrTiO 3 , легированного ря-дом 3d-элементов (Mn, Fe, Co, Ni) [8][9][10][11][12][13], показали, что легирование SrTiO 3 вызывает сильное поглощение света в видимой области спектра, причем наиболее ярко этот эффект выражен в случае примесей Co и Ni.…”

Applications of ferroelectrics in photovoltaic devices

“…The most widely considered approach for alleviating the problem of high band gap is the cation substitution approach. This approach allows to reduce the band gap of the materials without affecting their ferroelectricity [41][42][43]. After transition metal substitutions of perovskite B-site ions, perovskite oxides can generate various semiconducting ferroelectric oxides [44].…”