Origin of ferroelectricity in perovskites: The principal problems from a theoretical perspective

Cohen, R. E.

doi:10.1080/00150199308008689

Cited by 16 publications

(6 citation statements)

References 32 publications

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“…The electronic structure of BaTiO 3 has been the subject of some experimental and theoretical studies [1,2,[7][8][9][10][11][12][13][14][15][16]. There has been considerable progress in achieving an understanding of the lattice dynamics and the origin of the ferroelectricity from firstprinciples total-energy calculations.…”

Section: Introductionmentioning

confidence: 99%

Ab initiocalculations of the electronic structure and optical properties of ferroelectric tetragonal

Bagayoko

Zhao

Fan

et al. 1998

J. Phys.: Condens. Matter

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The electronic structure, charge distribution, effective charge, and charge transfer in ferroelectric tetragonal BaTiO 3 are carefully studied using a local density functional potential and a self-consistent ab initio LCAO (linear combination of atomic orbitals) method. It is shown that the band gap and low-energy conduction band can be calculated with a reasonable accuracy when the ab initio LCAO method is used with an optimum basis set of atomic orbitals. The calculated optical spectrum, band gap, and effective mass of BaTiO 3 , obtained from the calculated electronic structure, are in good agreement with experimental results.

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Section: Introductionmentioning

confidence: 99%

Ab initiocalculations of the electronic structure and optical properties of ferroelectric tetragonal

Bagayoko

Zhao

Fan

et al. 1998

J. Phys.: Condens. Matter

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“…First-principles electronic structure approaches have been very successful for bulk ferroelectrics [14][15][16][17][18][19][20][21] but the application of first-principles band structure methods to surface properties is daunting due to the giant computational burden. Here the first set of accurate electronic structure calculations for periodic BaTiO 3 slabs are presented.…”

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confidence: 99%

Surface effects in ferroelectrics: Periodic slab computations for BaTiO₃

Cohen

1997

Ferroelectrics

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Total energies, electronic structure, surface energies, polarization, potentials and charge densities were studied for slabs of BaTiO 3 using the Linearized Augmented Plane Wave (LAPW) method. The depolarization field inhibits ferroelectricity in the slabs, and the macroscopic field set up across a ferroelectric slab is sufficient to cause electronic states to span the gap and give a metallic band structure, but the band shifts are not rigid and O p states tend to pile up at the Fermi level. There are electronic surface states, especially evident on TiO 2 surfaces. The dangling bonds bond back to the surface Ti's and make the surface stable and reactive. The BaO surfaces are more ionic than the bulk. I. INTRODUCTIONSurfaces of ferroelectrics can strongly effect their properties. In general this is a much stronger effect than in paraelectric materials, because the termination of a ferroelectric gives rise to a depolarization field, which is huge in an ideal, ionic ferroelectric. The depolarization field, E d, is opposite in sign to the bulk polarization, and gives a contribution to the energy of −E d ·P large enough to completely destabilize the bulk ferroelectric state 1,2 . The ferroelectric 1 distortion in thin films varies with thickness so that the structures become cubic at thin edges 3 . Huge particle size effects are observed 4,5 , orders of magnitude greater than observed for non-ferroelectrics. Surfaces are important also during crystal growth, and their properties are key to catalysis and use as a epitaxial substrate. Here we study thin slabs of BaTiO 3 to better understand the electronic structure of the surface, surface energetics and relaxation, and intrinsic screening of the depolarization field.Experimental studies of BaTiO 3 surfaces are few and many more studies have focused on SrTiO 3 which lacks the complications of ferroelectricity. Photoemission studies of sputtered and annealed BaTiO 3 show evidence of significant surface defects 6 , and a number of papers have addressed the defect properties of the surface 7-9 . Studies of SrTiO 3 surfaces show evidence for minor relaxations by motions of atoms perpendicular to the surfaces 10,11 and show no evidence for states in the gap. 12 Some recent studies of BaTiO 3 show evidence for gap states 8 , and others do not 13 , probably indicating sensitivity to the surface defect state. Photoemission spectroscopy on BaTiO 3 shows excellent agreement with bulk LAPW computations of the LDA band structure 13 .First-principles electronic structure approaches have been very successful for bulk ferroelectrics 14-21 but the application of first-principles band structure methods to surface properties is daunting due to the giant computational burden. Here the first set of accurate electronic structure calculations for periodic BaTiO 3 slabs are presented. These results can be considered benchmark results for faster, more approximate methods, and also give some insights into the electronic structure of ferroelectric BaTiO 3 surfaces. II. METHODWe studied six to sev...

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“…The presence of lesser space charge polarization in lanthanum doped samples is possibly because of charge neutrality in lanthanum doped sample and high La-O bond strength so that these ions are relatively less free to cascade near to grain boundary and sample electrode interfaces. The absence of space charge in the lead doped sample is possibly due to similar valence state of lead with that of strontium and due to the covalent nature of Pb-O bond [28]. The described as the characteristic of tetragonal crystal systems in detail in many publications of Cohen et al and others [29][30][31].…”

Section: Methodsmentioning

confidence: 93%

Electrical Investigations of Aurivillius Type Sr_0.7A_0.3Bi₂Nb₂O₉(A = Ca, La and Pb) Ferroelectric Ceramics

Shrivastava

Jha

Mendiratta³

2007

Ferroelectrics

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Aurivillius type bismuth layer structured ferroelectrics (BLSF) have been found to possess strong relationship between tetragonal strain (c/a) and extrinsic/ intrinsic conductivity. The extrinsic part of the conductivity is known to depend upon space charge in the sample. The present paper discusses effects of 30 atomic % doping of Ca, La and Pb on tetragonal strain, conductivity and dielectric constant/loss with temperature and frequency. Tetragonal strain increases on doping calcium and lead while it shows a decrease on doping lanthanum. The calcium and lanthanum doped samples show pronounced space charge part of dielectric constant while lead doped sample shows nearly constant permittivity values. No phase transition is observed in the calcium doped sample up to 600 • C while for the lanthanum doped sample a decrease of 141 • C is observed in the value of Curie temperature compared to that for the undoped sample.

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Origin of ferroelectricity in perovskites: The principal problems from a theoretical perspective

Cited by 16 publications

References 32 publications

Ab initiocalculations of the electronic structure and optical properties of ferroelectric tetragonal

Ab initiocalculations of the electronic structure and optical properties of ferroelectric tetragonal

Surface effects in ferroelectrics: Periodic slab computations for BaTiO₃

Electrical Investigations of Aurivillius Type Sr_0.7A_0.3Bi₂Nb₂O₉(A = Ca, La and Pb) Ferroelectric Ceramics

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Origin of ferroelectricity in perovskites: The principal problems from a theoretical perspective

Cited by 16 publications

References 32 publications

Ab initiocalculations of the electronic structure and optical properties of ferroelectric tetragonal

Ab initiocalculations of the electronic structure and optical properties of ferroelectric tetragonal

Surface effects in ferroelectrics: Periodic slab computations for BaTiO3

Electrical Investigations of Aurivillius Type Sr0.7A0.3Bi2Nb2O9(A = Ca, La and Pb) Ferroelectric Ceramics

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Surface effects in ferroelectrics: Periodic slab computations for BaTiO₃

Electrical Investigations of Aurivillius Type Sr_0.7A_0.3Bi₂Nb₂O₉(A = Ca, La and Pb) Ferroelectric Ceramics