Proton transport and structural relations in hydroxyl-bearing BaTiO{sub 3} and its doped compositions synthesised by wet-chemical methods
Hydrothermally synthesised powders of BaTiO{sub 3} and its Fe- or Nd-doped analogues contain hydroxyl groups in the lattice substitutional to oxide ion, as confirmed from TGA/DTA, IR spectral analysis of D{sub 2}O-treated powders, EGA-MS, the contraction in lattice constant with heat treatment by XRD and surface examination by XPS. Electrical resistivity measurements were carried out on the pellets from 298 to 1000 K by ac impedance spectroscopy and dc methods in dry or moist air and 8% H{sub 2}+Ar environments. The electrical conductivity observed for unsintered pellets between 298 and 500 K, is in the range of 10{sup -3} to 10{sup -7} S/cm and can be attributed to the extrinsic hydroxyls in BaTiO{sub 3}. The acceptor-doped composition, BaTi{sub 0.9}Fe{sub 0.1}O{sub 3-{delta}}: 2{delta}(OH) exhibits higher electrical conductivity than BaTiO{sub 3} or the donor-doped Ba{sub 0.9}Nd{sub 0.1}TiO{sub 3-{delta}}: 2{delta}(OH) in moist air. The hydrothermally prepared powders heat treated below 1000 K having cubic symmetry at room temperature, possess higher proton conductivity and reabsorption capability for hydroxyls on exposure to moisture than the powders sintered at 1673 K (tetragonal symmetry). The conductivity at 298-500 K is due to the mobility of proton along O-H-O octahedra in the perovskite lattice. The conduction at 550-1000 K is a combined effect of proton as well as oxygen vacancy mobility in BaTiO{sub 3} and Ba{sub 0.9}Nd{sub 0.1}TiO{sub 3}; electron hole (Ti{sup 4+}, Ti{sup 3+}, Fe{sup 3+}, Fe{sup 2+}) participation is the additional contribution in acceptor-doped composition in this temperature range.
- OSTI ID:
- 20888033
- Journal Information:
- Materials Research Bulletin, Vol. 39, Issue 3; Other Information: DOI: 10.1016/j.materresbull.2003.10.004; PII: S0025540803003039; Copyright (c) 2003 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BARIUM OXIDES
DOPED MATERIALS
ELECTRIC CONDUCTIVITY
HEAT TREATMENTS
HEAVY WATER
HYDROTHERMAL SYNTHESIS
HYDROXIDES
IRON IONS
LATTICE PARAMETERS
PEROVSKITE
PROTON TRANSPORT
THERMAL GRAVIMETRIC ANALYSIS
TITANATES
TITANIUM IONS
TITANIUM OXIDES
VACANCIES
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY