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Hydrogen sensitivity of doped CuO/ZnO heterocontact sensors

Author Seymen Aygün and David Cann
Source
Sensors and Actuators B: Chemical
Volume: 106, Issue: 2, Pages: 837-842
Time of Publication: 2005
Abstract Heterocontact sensors based on p-type CuO and n-type ZnO ceramics have been shown to exhibit a high sensitivity to reducing gas species and an intrinsic selectivity. In this work, doped heterocontact sensors were prepared via solid state synthesis routes. CuO was doped with various monovalent (Li, Na) and isovalent (Ca, Sr, Ni) dopants at different compositions to form both single phase and two phase samples. Effects of dopants on hydrogen sensitivity through conductivity and heterogeneous microstructure were investigated using dc current–voltage measurements and ac impedance analysis. It was observed that both monovalent and divalent dopants increased the hydrogen sensitivity significantly. The highest sensitivity was observed in a 2.5 mol% Ni-CuO/ZnO heterocontact and low amounts of Li doping were shown to greatly enhance the rectifying characteristics.
Keywords Hydrogen sensor; Heterocontact; CuO; ZnO

Synthesis, densification and electrical properties of strontium cerate ceramics

Authors Paul Inge Dahl, 1, Reidar Haugsrud, Hilde Lea Lein, Tor Grande, Truls Norby and Mari-Ann Einarsrud
Source
Journal of the European Ceramic Society
Volume: 27, Issue: 16, Pages: 4461-4471
Time of Publication: 2007

Stability and conductivity study of the BaCe0.9−xZrxY0.1O2.95 systems

Author Zhimin Zhong
Source
Solid State Ionics
Volume: 178, Issue: 3-4, Pages: 213-220
Time of Publication: 2007

Defects and transport properties in Ln6WO12 (Ln = La, Nd, Gd, Er)

Author Reidar Haugsrud
Source
Solid State Ionics
Volume: 178, Issue: 7-10, Pages: 555-560
Time of Publication: 2007

Phase transitions and ferroelectric properties in BiScO3-Bi(Zn1/2Ti1/2)O3-BaTiO3 solid solutions

Authors Chien-Chih Huang, David P. Cann, Xiaoli Tan, and Naratip Vittayakorn
Source
Journal of Applied Physics
Volume: 102, Issue: 4, Pages: 044103
Time of Publication: 2007

Shrinkage Effects of the Conduction Zone in the Electrical Properties of Metal Oxide Nanocrystals: The Basis for Room Temperature Conductometric Gas Sensor

Authors M. Manzanares, T. Andreu, J. D. Prades, J. Arbiol, F. Hernandez-Ramírez, A. Cirera and J. R. Morante
Source
Journal of Sensors
Volume: 2009, Pages: 1-7, doi:10.1155/2009/783675
Time of Publication: 2009

Preparation, electrical and thermal properties of new exfoliated graphite-based composites

Authors I.М. Afanasov, V.А. Morozov, A.V. Kepman, S.G. Ionov, A.N. Seleznev, G. Van Tendeloo and V.V. Avdeev
Source
Carbon
Volume: 47, Issue: 1, Pages: 263-270
Time of Publication: 2009

Structure, defect chemistry, and proton conductivity in nominally Sr-doped Ba3La(PO4)3

Authors N. Sharova, H. Fjellvåg, T. Norby
Source
Solid State Ionics
Volume: 180, Issue: 4-5, Pages: 338-342
Time of Publication: 2009

Local structure and ionic conductivity in the Zr2Y2O7–Y3NbO7 system

Authors Stefan T Norberg, Istaq Ahmed, Stephen Hull, Dario Marrocchelli and Paul A Madden
Source
Journal of Physics: Condensed Matter
Volume: 21, Issue: 21, Pages: 215401
Time of Publication: 2009

Thin film chemical sensors based on p-CuO/n-ZnO heterocontacts

Authors C.S. Dandeneau, Y.H. Jeon, C.T. Shelton, T.K. Plant, D.P. Cann and B.J. Gibbons
Source
Thin Solid Films
Volume: 517, Issue: 15, Pages: 4448-4454
Time of Publication: 2009

Phase formation, microstructure, and dielectric properties of (1 − x)PZT–(x)PCN ceramics

Authors A. Prasatkhetragarn, P. Ketsuwan, S. Ananta, R. Yimnirun and D.P. Cann
Source
Materials Letters
Volume: 63, Issue: 15, Pages: 1281-1284
Time of Publication: 2009

Characterization of porous lanthanum strontium manganite (LSM) and development of yttria stabilized zirconia (YSZ) coating

Authors A.K. Sahu, A. Ghosh and A.K. Suri
Source
Ceramics International
Volume: 35, Issue: 6, Pages: 2493-2497
Time of Publication: 2009

Ordering processes in Ln2TiO5 (Ln = Dy–Lu): The role of thermal history

Authors A.V. Shlyakhtina, D.A. Belov, O.K. Karyagina and L.G. Shcherbakova
Source
Journal of Alloys and Compounds
Volume: 479, Issue: 1-2, Pages: 6-10
Time of Publication: 2009

Effects of Zr/Ti ratio on dielectric and ferroelectric properties of 0.8Pb(ZrxTi1−x)O3–0.2Pb(Co1/3Nb2/3)O3 ceramics

Authors A. Prasatkhetragarna, M. Unruan, A. Ngamjarurojana, Y. Laosiritaworn, S. Ananta, R. Yimnirun and D. P. Cann
Source
Current Applied Physics
Volume: 9, Issue: 4, Pages: 802-806
Time of Publication: 2009

Ce0.9Sr0.1VOx (x = 3, 4) as anode materials for H2S-containing CH4 fueled solid oxide fuel cells

Authors Nemanja Danilovic, Jing-Li Luo, Karl T. Chuang and Alan R. Sanger
Source
Journal of Power Sources
Volume: 192, Issue: 2, Pages: 247-257
Time of Publication: 2009

Acceptor doping of Ln2Ti2O7 (Ln = Dy, Ho, Yb) pyrochlores with divalent cations (Mg, Ca, Sr, Zn)

Authors D.A. Belov, A.V. Shlyakhtina, S.Yu. Stefanovich, I.V. Kolbanev, Yu.A. Belousov, O.K. Karyagina and L.G. Shcherbakova
Source
Materials Research Bulletin
Volume: 44, Issue: 8, Pages: 1613-1620
Time of Publication: 2009

Effect of substitution with Cr3+ and addition of Ni on the physical and electrochemical properties of Ce0.9Sr0.1VO3 as a H2S-active anode for solid oxide fuel cells

Authors N. Danilovic, J.L. Luo, K. T. Chuang and A. R. Sanger
Source
Journal of Power Sources
Volume: 194, Issue: 1, Pages: 252-262
Time of Publication: 2009

Dielectric and ferroelectric properties of 0.8PZT–0.2PCN ceramics under sintering conditions variation

Authors A. Prasatkhetragarna, M. Unruan, A. Ngamjarurojana, Y. Laosiritaworn, S. Ananta, R. Yimnirun and D. P. Cann
Source
Current Applied Physics
Volume: 9, Issue: 5, Pages: 1165-1169
Time of Publication: 2009

Conductivity and water uptake of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O

Authors Niina Jalarvo, Camilla Haavik, Camilla Kongshaug, Poul Norby and Truls Norby
Source
Solid State Ionics
Volume: 180, Issue: 20-22, Pages: 1151-1156
Time of Publication: 2009

Synthesis and characterization of nanocrystalline Ni–YSZ cermet anode for SOFC

Author T. Priyatham and Ranjit Bauri
Source
Materials Characterization
Volume: 61, Issue: 1, Pages: 54-58
Time of Publication: 2010-01
Abstract Ni–YSZ cermet anode has been synthesized in one step using a simple and cost effective combustion synthesis process. The processed powder of NiO–YSZ is found to be nanocrystalline with crystallite sizes of 29 and 22 nm for NiO and YSZ respectively by X-ray diffraction and transmission electron microscopy analysis. X-ray diffraction analysis also shows that the precursor salts are converted to highly crystalline phases of NiO and YSZ (8 mol% Y2O3) without any intermediate calcination step and no undesirable phases are present. Comparison with the X-ray diffraction pattern of a commercial YSZ sample shows that the process is also effective in maintaining a close compositional control. The microstructure of the sintered and reduced sample shows a well defined network of pores which is necessary for the effective functioning of the anode. The electrical conductivity as a function of temperature shows metallic behavior.
Keywords Ni–YSZ anode; Combustion synthesis; Nanocrystalline cermet; Microstructure

A combined conductivity and DFT study of protons in PbZrO3 and alkaline earth zirconate perovskites

Authors Tor S. Bjørheim, Akihide Kuwabara, Istaq Ahmed, Reidar Haugsrud, Svein Stølen and Truls Norby
Source
Solid State Ionics
Volume: 181, Issue: 3-4, Pages: 130-137
Time of Publication: 2010
Abstract The electrical properties of nominally undoped and 4 mol% Y-doped PbZrO3 have been investigated by AC conductivity measurements and impedance spectroscopy under various pH2O and pO2 at high temperatures. The results indicate that the defect structures are dominated by acceptors (Y dopant and/or Pb vacancies formed during synthesis). In dry atmosphere and at high temperatures, the acceptors are compensated by oxygen vacancies. These are hydrated and replaced by protonic defects (hydroxide ions on oxide ion sites) at higher pH2O and lower temperatures. In oxidizing atmospheres, a minority concentration of electron holes dominates the conductivity. At lower temperatures and in wet atmosphere, a significant protonic conductivity contribution is also observed. Based on pO2 and pH2O isotherms, a model for incorporation of protonic defects has been applied, and the standard enthalpy of hydration of oxygen vacancies in undoped PbZrO3 has been determined (− 1.07 ± 0.13 eV). The measured total conductivities are influenced by high grain boundary resistance. Hence, the enthalpy is at the present stage assigned to the polycrystalline ceramic material as such. Rough estimates of bulk proton mobility in Y-doped PbZrO3 yield uH+0 = 17 cm2K/Vs and ΔHm,H+ = 0.93 eV. A complementary DFT study of the hydration thermodynamics of PbZrO3 and the alkaline earth zirconate perovskites AZrO3 (A = Ca, Sr, Ba) is also reported. The experimental and theoretical hydration enthalpies are compared with those of other ABO3 perovskites. Correlations between the hydration thermodynamics and other properties of the materials are discussed.
Keywords PbZrO3; CaZrO3; SrZrO3; BaZrO3; Conductivity; Proton; Proton mobility; DFT; Thermodynamics; Defects; Hydration

Electrical conductivity and oxygen permeation properties of SrCoFeOx membranes

Authors Jay Kniep, Qinghua Yin, Izumi Kumakiri and Y.S. Lin
Source
Solid State Ionics
Volume: 180, Issue: 40, Pages: 1633-1639
Time of Publication: 2010
Abstract The total conductivity and oxygen permeation properties of dense SrCoFeOx membranes synthesized from the solid state method were studied in the temperature range of 700–900 °C. The SrCoFeOx membranes consist of an intergrowth (Sr4Fe6 − xCoxO13 ± δ), perovskite (SrFe1 − xCoxO3 − δ), and spinel (Co3 − xFexO4) phase. SrCoFeOx exhibits n-type and p-type conduction at low and high oxygen partial pressures, respectively, and has a total conductivity of 16.5 S/cm at 900 °C in air. The oxygen permeation fluxes for SrCoFeOx and SrFeCo0.5Ox membranes were measured with either an inert or carbon monoxide sweep gas. The oxygen permeation fluxes were higher through SrCoFeOx membranes than SrFeCo0.5Ox membranes and can be attributed to a difference in the amount and makeup of the perovskite phase present in each composition. The oxygen permeation fluxes with a carbon monoxide sweep gas were approximately two orders of magnitude larger than the fluxes measured with an inert sweep gas for both compositions. The large oxygen permeation fluxes observed with a carbon monoxide sweep are due to a higher driving force for oxygen transport and a reaction on the sweep side of the membrane that maintains a low oxygen partial pressure.
Keywords Mixed-conducting oxide membrane; Oxygen permeation; Strontium iron cobalt oxide

Transport properties and defect analysis of La1.9Sr0.1NiO4 + δ

Authors Zuoan Li, Reidar Haugsrud, Jens B. Smith and Truls Norby
Source
Solid State Ionics
Volume: 180, Issue: 26-27, Pages: 1433-1441
Time of Publication: 2009

Investigation of proton conductivity in Sm1.92Ca0.08Ti2O7 − δ and Sm2Ti1.92Y0.08O7 − δ pyrochlores

Authors K.E.J. Eurenius, E. Ahlberg, I. Ahmed, S.G. Eriksson and C.S. Knee
Source
Solid State Ionics
Volume: 181, Issue: 3-4, Pages: 148-153
Time of Publication: 2010
Abstract The results of the synthesis and characterisation of pyrochlore systems Sm1.92Ca0.08Ti2O7 − δ and Sm2Ti1.92Y0.08O7 − δ are reported. The electrical conductivity of the materials was studied using impedance spectroscopy under wet and dry oxygen and argon. Enhancements of the bulk conductivity at temperatures up to 500 °C were observed for wet conditions indicative of significant proton conductivity. The presence of dissolved protons in the materials is supported by thermogravimetric analysis and infrared spectroscopy. Proton conduction was confirmed by measurements in O2/D2O and Ar/D2O. The results reveal the importance of the correct choice of dopant site for the pyrochlore structure, with A-site substitution yielding the highest levels of proton, as well as oxide ion, conduction. For both samples bulk, rather than grain boundary, conduction is found to be dominant.
Keywords Sm2Ti2O7; Pyrochlore; Ionic conductivity; Infrared spectroscopy; Impedance spectroscopy

Space–charge theory applied to the grain boundary impedance of proton conducting BaZr0.9Y0.1O3 − δ

Authors C. Kjolseth, , H. Fjeld, O. Prytz, P.I. Dahl, C. Estournes, R. Haugsrud, T. Norby
Source
Solid State Ionics
Volume: 181, Issue: 5-7, Pages: 268-275
Time of Publication: 2010
Abstract The specific grain interior and grain boundary conductivities, obtained from impedance spectroscopy and the brick layer model, are reported for BaZr0.9Y0.1O3 − δ as a function of pO2 and temperature. pO2-dependencies were indicative of dominating ionic and p-type electronic conduction for the grain interior under reducing and oxidizing conditions, respectively, while the grain boundaries showed an additional n-type electronic contribution under reducing conditions. Transmission electron microscopy revealed enrichment of Y in the grain boundary region. These findings indicate the existence of space–charge layers in the grain boundaries. A grain boundary core–space–charge layer model is therefore applied to interpret the data. Using a Mott–Schottky approximation, a Schottky barrier height of 0.5–0.6 V and an effective grain boundary width of 8–10 nm (= 2× space–charge layer thickness) is obtained at 250 °C in wet oxygen. Finite-element modelling of the complex impedance over a grain boundary with a space–charge layer depletion of protons yields a distorted semicircle as observed in the impedance spectra.
Keywords BaZrO3; BaZr0.9Y0.1O3 − δ; Proton conductivity; Grain boundary resistance; Impedance spectroscopy; Space–charge layer
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