Crystal structure and its role in electrical properties of the perovskite CaPbO3 synthesized at high pressure

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Abstract

The orthorhombic modification of CaPbO3 was synthesized from a mixture of Ca2PbO4 and PbO2 at high temperature and high pressure. Its structure was analyzed by Rietveld analysis of neutron diffraction data on the basis of space group Pbnm. It has a distorted perovskite structure of the GdFeO3 type and a unit cell with dimensions of a = 5.6710 Å, b = 5.8875 Å, and c = 8.1495 Å. The Pb-O bond lengths in each PbO6 octahedron are comparable to each other, whereas the PbO6 octahedron tilts around [110]p and [001]p axes (p: perovskite subcell) by 18.50° and 20.28°, respectively. These tilt angles, which show great structural distortion in CaPbO3 containing the smaller Ca2+ ion, are much larger than corresponding ones in crystal chemically isotypic SrPbO3. The electric resistivity of CaPbO3 at room temperature was as high as 3 × 103 Ω·cm, which is in sharp contrast to low resistivities observed in other perovskite-type oxides BaPbO3 and SrPbO3. The high resistivity of CaPbO3 is explained as gap formation between 2p(O) nonbonding and 6s(Pb)-2p(O) spσ antibonding bands, which overlap with each other in BaPbO3. Solid solutions, where Sr2+, La3+, Nd3+, and Y3+ ions were partially substituted for Ca2+ ions, were also prepared to examine structural and electrical properties in perovskites based on CaPbO3. Substitution of Sr2+ for Ca2+ led to reductions in the distortion and gap energy, whereas that of La3+, Nd3+, and Y3+ induced metallic conductivity owing to doping of electron carriers into the antibonding band.

Original languageEnglish
Pages (from-to)747-753
Number of pages7
JournalChemistry of Materials
Volume11
Issue number3
Publication statusPublished - 1999
Externally publishedYes

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Perovskite
Electric properties
Crystal structure
Ions
Rietveld analysis
Electric conductivity
Bond length
Neutron diffraction
Oxides
Structural properties
Solid solutions
Energy gap
Substitution reactions
Doping (additives)
Temperature
Crystals
Electrons
perovskite

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

Cite this

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title = "Crystal structure and its role in electrical properties of the perovskite CaPbO3 synthesized at high pressure",
abstract = "The orthorhombic modification of CaPbO3 was synthesized from a mixture of Ca2PbO4 and PbO2 at high temperature and high pressure. Its structure was analyzed by Rietveld analysis of neutron diffraction data on the basis of space group Pbnm. It has a distorted perovskite structure of the GdFeO3 type and a unit cell with dimensions of a = 5.6710 {\AA}, b = 5.8875 {\AA}, and c = 8.1495 {\AA}. The Pb-O bond lengths in each PbO6 octahedron are comparable to each other, whereas the PbO6 octahedron tilts around [110]p and [001]p axes (p: perovskite subcell) by 18.50° and 20.28°, respectively. These tilt angles, which show great structural distortion in CaPbO3 containing the smaller Ca2+ ion, are much larger than corresponding ones in crystal chemically isotypic SrPbO3. The electric resistivity of CaPbO3 at room temperature was as high as 3 × 103 Ω·cm, which is in sharp contrast to low resistivities observed in other perovskite-type oxides BaPbO3 and SrPbO3. The high resistivity of CaPbO3 is explained as gap formation between 2p(O) nonbonding and 6s(Pb)-2p(O) spσ antibonding bands, which overlap with each other in BaPbO3. Solid solutions, where Sr2+, La3+, Nd3+, and Y3+ ions were partially substituted for Ca2+ ions, were also prepared to examine structural and electrical properties in perovskites based on CaPbO3. Substitution of Sr2+ for Ca2+ led to reductions in the distortion and gap energy, whereas that of La3+, Nd3+, and Y3+ induced metallic conductivity owing to doping of electron carriers into the antibonding band.",
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T1 - Crystal structure and its role in electrical properties of the perovskite CaPbO3 synthesized at high pressure

AU - Yamamoto, Ayako

PY - 1999

Y1 - 1999

N2 - The orthorhombic modification of CaPbO3 was synthesized from a mixture of Ca2PbO4 and PbO2 at high temperature and high pressure. Its structure was analyzed by Rietveld analysis of neutron diffraction data on the basis of space group Pbnm. It has a distorted perovskite structure of the GdFeO3 type and a unit cell with dimensions of a = 5.6710 Å, b = 5.8875 Å, and c = 8.1495 Å. The Pb-O bond lengths in each PbO6 octahedron are comparable to each other, whereas the PbO6 octahedron tilts around [110]p and [001]p axes (p: perovskite subcell) by 18.50° and 20.28°, respectively. These tilt angles, which show great structural distortion in CaPbO3 containing the smaller Ca2+ ion, are much larger than corresponding ones in crystal chemically isotypic SrPbO3. The electric resistivity of CaPbO3 at room temperature was as high as 3 × 103 Ω·cm, which is in sharp contrast to low resistivities observed in other perovskite-type oxides BaPbO3 and SrPbO3. The high resistivity of CaPbO3 is explained as gap formation between 2p(O) nonbonding and 6s(Pb)-2p(O) spσ antibonding bands, which overlap with each other in BaPbO3. Solid solutions, where Sr2+, La3+, Nd3+, and Y3+ ions were partially substituted for Ca2+ ions, were also prepared to examine structural and electrical properties in perovskites based on CaPbO3. Substitution of Sr2+ for Ca2+ led to reductions in the distortion and gap energy, whereas that of La3+, Nd3+, and Y3+ induced metallic conductivity owing to doping of electron carriers into the antibonding band.

AB - The orthorhombic modification of CaPbO3 was synthesized from a mixture of Ca2PbO4 and PbO2 at high temperature and high pressure. Its structure was analyzed by Rietveld analysis of neutron diffraction data on the basis of space group Pbnm. It has a distorted perovskite structure of the GdFeO3 type and a unit cell with dimensions of a = 5.6710 Å, b = 5.8875 Å, and c = 8.1495 Å. The Pb-O bond lengths in each PbO6 octahedron are comparable to each other, whereas the PbO6 octahedron tilts around [110]p and [001]p axes (p: perovskite subcell) by 18.50° and 20.28°, respectively. These tilt angles, which show great structural distortion in CaPbO3 containing the smaller Ca2+ ion, are much larger than corresponding ones in crystal chemically isotypic SrPbO3. The electric resistivity of CaPbO3 at room temperature was as high as 3 × 103 Ω·cm, which is in sharp contrast to low resistivities observed in other perovskite-type oxides BaPbO3 and SrPbO3. The high resistivity of CaPbO3 is explained as gap formation between 2p(O) nonbonding and 6s(Pb)-2p(O) spσ antibonding bands, which overlap with each other in BaPbO3. Solid solutions, where Sr2+, La3+, Nd3+, and Y3+ ions were partially substituted for Ca2+ ions, were also prepared to examine structural and electrical properties in perovskites based on CaPbO3. Substitution of Sr2+ for Ca2+ led to reductions in the distortion and gap energy, whereas that of La3+, Nd3+, and Y3+ induced metallic conductivity owing to doping of electron carriers into the antibonding band.

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