skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: High-temperature order-disorder transition and polaronic conductivity in PrBaCo{sub 2}O{sub 5.48}

Abstract

Neutron powder diffraction and transport measurements have been used to investigate the PrBaCo{sub 2}O{sub 5.48} compound between room temperature and 820 K. A structural phase transition, involving a rearrangement of oxygen vacancies, was found at T{sub OD}=776 K. Across the transition the perovskite structure loses its vacancy ordering, and the crystal symmetry changes from orthorhombic Pmmm to tetragonal P4/mmm. The resistivity measurements for temperatures above {approx}350 K yield high values of {rho}, indicating that the compound is rather semiconducting than metallic as usually accepted. A model in terms of thermally activated hole (polaronic) hopping is proposed.

Authors:
; ; ;  [1]; ; ;  [2];  [3];  [2]; ; ;  [4]
  1. Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)
  2. Laboratory for Developments and Methods, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)
  3. (Switzerland)
  4. Institute of Solid State Chemistry RAS, Ekaterinburg 620219 (Russian Federation)
Publication Date:
OSTI Identifier:
20787957
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 73; Journal Issue: 9; Other Information: DOI: 10.1103/PhysRevB.73.094203; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BARIUM COMPOUNDS; COBALT OXIDES; CRYSTALS; ELECTRIC CONDUCTIVITY; HOLES; NEUTRON DIFFRACTION; ORDER-DISORDER TRANSFORMATIONS; ORTHORHOMBIC LATTICES; OXYGEN; PEROVSKITE; POLARONS; PRASEODYMIUM COMPOUNDS; SYMMETRY; TEMPERATURE DEPENDENCE; TETRAGONAL LATTICES; VACANCIES

Citation Formats

Streule, S., Podlesnyak, A., Sheptyakov, D., Mesot, J., Pomjakushina, E., Stingaciu, M., Medarde, M., Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institut, CH-5232 Villigen PSI, Conder, K., Patrakeev, M. V., Leonidov, I. A., and Kozhevnikov, V. L.. High-temperature order-disorder transition and polaronic conductivity in PrBaCo{sub 2}O{sub 5.48}. United States: N. p., 2006. Web. doi:10.1103/PHYSREVB.73.0.
Streule, S., Podlesnyak, A., Sheptyakov, D., Mesot, J., Pomjakushina, E., Stingaciu, M., Medarde, M., Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institut, CH-5232 Villigen PSI, Conder, K., Patrakeev, M. V., Leonidov, I. A., & Kozhevnikov, V. L.. High-temperature order-disorder transition and polaronic conductivity in PrBaCo{sub 2}O{sub 5.48}. United States. doi:10.1103/PHYSREVB.73.0.
Streule, S., Podlesnyak, A., Sheptyakov, D., Mesot, J., Pomjakushina, E., Stingaciu, M., Medarde, M., Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institut, CH-5232 Villigen PSI, Conder, K., Patrakeev, M. V., Leonidov, I. A., and Kozhevnikov, V. L.. Wed . "High-temperature order-disorder transition and polaronic conductivity in PrBaCo{sub 2}O{sub 5.48}". United States. doi:10.1103/PHYSREVB.73.0.
@article{osti_20787957,
title = {High-temperature order-disorder transition and polaronic conductivity in PrBaCo{sub 2}O{sub 5.48}},
author = {Streule, S. and Podlesnyak, A. and Sheptyakov, D. and Mesot, J. and Pomjakushina, E. and Stingaciu, M. and Medarde, M. and Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institut, CH-5232 Villigen PSI and Conder, K. and Patrakeev, M. V. and Leonidov, I. A. and Kozhevnikov, V. L.},
abstractNote = {Neutron powder diffraction and transport measurements have been used to investigate the PrBaCo{sub 2}O{sub 5.48} compound between room temperature and 820 K. A structural phase transition, involving a rearrangement of oxygen vacancies, was found at T{sub OD}=776 K. Across the transition the perovskite structure loses its vacancy ordering, and the crystal symmetry changes from orthorhombic Pmmm to tetragonal P4/mmm. The resistivity measurements for temperatures above {approx}350 K yield high values of {rho}, indicating that the compound is rather semiconducting than metallic as usually accepted. A model in terms of thermally activated hole (polaronic) hopping is proposed.},
doi = {10.1103/PHYSREVB.73.0},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 9,
volume = 73,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2006},
month = {Wed Mar 01 00:00:00 EST 2006}
}
  • The Er{sub 2+x}Ti{sub 2-x}O{sub 7-{delta}} (x = 0.096; 35.5 mol% Er{sub 2}O{sub 3}) solid solution and the stoichiometric pyrochlore-structured compound Er{sub 2}Ti{sub 2}O{sub 7} (x = 0; 33.3 mol% Er{sub 2}O{sub 3}) are characterized by X-ray diffraction (phase analysis and Rietveld method), thermal analysis and optical spectroscopy. Both oxides were synthesized by thermal sintering of co-precipitated powders. The synthesis study was performed in the temperature range 650-1690 deg. C. The amorphous phase exists below 700 deg. C. The crystallization of the ordered pyrochlore phase (P) in the range 800-1000 deg. C is accompanied by oxygen release. The ordered pyrochlore phasemore » (P) exists in the range 1000-1200 deg. C. Heat-treatment at T {>=} 1600 deg. C leads to the formation of an oxide ion-conducting phase with a distorted pyrochlore structure (P2) and an ionic conductivity of about 10{sup -3} S/cm at 740 deg. C. Complex impedance spectra are used to separately assess the bulk and grain-boundary conductivity of the samples. At 700 deg. C and oxygen pressures above 10{sup -10} Pa, the Er{sub 2+x}Ti{sub 2-x}O{sub 7-{delta}} (x = 0, 0.096) samples are purely ionic conductors.« less
  • The order-disorder transition involving oxygen atoms and vacancies in the Cu-O basal planes of the superconductor Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 6+//sub delta/ was studied under several oxygen partial pressures. The transition is second order in nature, shows small hysteresis probably due to twin boundary kinetics, and always occurs at the same oxygen concentration. The average site energy for an oxygen atom in the lattice is -3.41 eV. No superconductivity is found for a fully disordered sample.
  • The oxygen content, conductivity and thermopower in the double perovskite-like cobaltite PrBaCo{sub 2}O{sub 5+{delta}} are reported in the oxygen partial pressure range 2x10{sup -6}-0.21 atm and temperatures between 650 and 950 deg. C. The electrical properties are shown to be continuous through the transition from {delta}>0.5 to {delta}<0.5. The variations of transport parameters with temperature and oxygen content reveal hole polaron hopping conduction within oxygen non-stoichiometry domain {delta}<0.5. - Graphical abstract: Electrical properties in PrBaCo{sub 2}O5+{delta} depending on oxygen content at 800 deg. C. Highlights: > The oxygen content in PrBaCo{sub 2}O{sub 5+{delta}} is studied depending on temperature and oxygenmore » partial pressure. > The transport parameter variations reveal hole polaron conduction. > The electrical properties are continuous through the transition from {delta}>0.5 to {delta}<0.5.« less
  • The crystal structure of the layered cobaltite HoBaCo{sub 2}O{sub 5.5} (substituted with both {sup 16}O and {sup 18}O) was studied across an insulator to metal (MI) transition at T{sub MI}=305 K employing high-resolution neutron diffraction. We have found that the transition at T{sub MI} is of the first-order type, accompanied by an abrupt negative change of the unit cell volume ({approx}0.15%) and melting of the orbital order in the pyramids. The existence of an isotope effect on T{sub MI} suggests that the structure changes are caused by the electron delocalization above the transition.
  • The interest in Cu2ZnSn(S,Se)4 (CZTS) for photovoltaic applications is motivated by similarities to Cu(In,Ga)Se2 while being comprised of non-toxic and earth abundant elements. However, CZTS suffers from a Voc deficit, where the Voc is much lower than expected based on the band gap, which may be the result of a high concentration of point-defects in the CZTS lattice. Recently, reports have observed a low-temperature order/disorder transition by Raman and optical spectroscopies in CZTS films and is reported to describe the ordering of Cu and Zn atoms in the CZTS crystal structure. To directly determine the level of Cu/Zn ordering, wemore » have used resonant-XRD, a site, and element specific probe of long range order. We used CZTSe films annealed just below and quenched from just above the transition temperature; based on previous work, the Cu and Zn should be ordered and highly disordered, respectively. Our data show that there is some Cu/Zn ordering near the low temperature transition but significantly less than high chemical order expected from Raman. To understand both our resonant-XRD results and the Raman results, we present a structural model that involves antiphase domain boundaries and accommodates the excess Zn within the CZTS lattice.« less