Cation non-stoichiometry in yttrium-doped barium zirconate: Phase behavior, microstructure, and proton conductivity

Yoshihiro Yamazaki, Raul Hernandez-Sanchez, Sossina M. Haile

Research output: Contribution to journalArticle

114 Citations (Scopus)

Abstract

Recent literature indicates that cation non-stoichiometry in proton-conducting perovskite oxides (ABO3) can strongly influence their transport properties. Here we have investigated A-site non-stoichiometry in Ba1-xZr0.8Y0.2O3-δ, a candidate electrolyte material for fuel cell and other electrochemical applications. Synthesis is performed using a chemical solution approach in which the barium deficiency is precisely controlled. The perovskite phase is tolerant to barium deficiency up to x = 0.06 as revealed by X-ray diffraction analysis, but accommodates the non-stoichiometry by incorporation of yttrium on the A-site. The dopant partitioning can explain the decrease in cell constant with increasing x, the decrease in proton conductivity (the latter as measured by a.c. impedance spectroscopy under humidified atmosphere), and the decrease in grain size in the sintered compacts. Within the single-phase region barium deficiency also has a detrimental impact on grain boundary conductivity, as a result both of the decreased grain size, leading to a higher number density of grain boundaries and of an increased per boundary resistivity. At higher values of x, a two phase system is observed, with yttria appearing as the predominant secondary phase and the barium zirconate reverting to an undoped composition. From the relative concentrations of the observed phases and their lattice constants, the ternary phase behavior at 1600°C (the sintering temperature) is generated. Both the bulk and grain boundary conductivities are sharply lower in the two-phase system than in the single phase compositions. The control over processing conditions demonstrates that it is possible to reproducibly prepare large-grained, stoichiometric BaZr0.8Y0.2O 3-δ with a total conductivity of 1 × 10-2 Scm-1 at 450°C, while revealing the mechanisms by which barium deficiency degrades properties.

Original languageEnglish
Pages (from-to)8158-8166
Number of pages9
JournalJournal of Materials Chemistry
Volume20
Issue number37
DOIs
Publication statusPublished - Oct 7 2010

Fingerprint

Barium zirconate
Yttrium
Proton conductivity
Barium
Phase behavior
Cations
Positive ions
Microstructure
Grain boundaries
Perovskite
Yttrium oxide
Phase composition
Transport properties
Oxides
X ray diffraction analysis
Electrolytes
Lattice constants
Protons
Fuel cells
Sintering

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

Cite this

Cation non-stoichiometry in yttrium-doped barium zirconate : Phase behavior, microstructure, and proton conductivity. / Yamazaki, Yoshihiro; Hernandez-Sanchez, Raul; Haile, Sossina M.

In: Journal of Materials Chemistry, Vol. 20, No. 37, 07.10.2010, p. 8158-8166.

Research output: Contribution to journalArticle

@article{10436eb1575040c8873160d1508af480,
title = "Cation non-stoichiometry in yttrium-doped barium zirconate: Phase behavior, microstructure, and proton conductivity",
abstract = "Recent literature indicates that cation non-stoichiometry in proton-conducting perovskite oxides (ABO3) can strongly influence their transport properties. Here we have investigated A-site non-stoichiometry in Ba1-xZr0.8Y0.2O3-δ, a candidate electrolyte material for fuel cell and other electrochemical applications. Synthesis is performed using a chemical solution approach in which the barium deficiency is precisely controlled. The perovskite phase is tolerant to barium deficiency up to x = 0.06 as revealed by X-ray diffraction analysis, but accommodates the non-stoichiometry by incorporation of yttrium on the A-site. The dopant partitioning can explain the decrease in cell constant with increasing x, the decrease in proton conductivity (the latter as measured by a.c. impedance spectroscopy under humidified atmosphere), and the decrease in grain size in the sintered compacts. Within the single-phase region barium deficiency also has a detrimental impact on grain boundary conductivity, as a result both of the decreased grain size, leading to a higher number density of grain boundaries and of an increased per boundary resistivity. At higher values of x, a two phase system is observed, with yttria appearing as the predominant secondary phase and the barium zirconate reverting to an undoped composition. From the relative concentrations of the observed phases and their lattice constants, the ternary phase behavior at 1600°C (the sintering temperature) is generated. Both the bulk and grain boundary conductivities are sharply lower in the two-phase system than in the single phase compositions. The control over processing conditions demonstrates that it is possible to reproducibly prepare large-grained, stoichiometric BaZr0.8Y0.2O 3-δ with a total conductivity of 1 × 10-2 Scm-1 at 450°C, while revealing the mechanisms by which barium deficiency degrades properties.",
author = "Yoshihiro Yamazaki and Raul Hernandez-Sanchez and Haile, {Sossina M.}",
year = "2010",
month = "10",
day = "7",
doi = "10.1039/c0jm02013c",
language = "English",
volume = "20",
pages = "8158--8166",
journal = "Journal of Materials Chemistry",
issn = "0959-9428",
publisher = "Royal Society of Chemistry",
number = "37",

}

TY - JOUR

T1 - Cation non-stoichiometry in yttrium-doped barium zirconate

T2 - Phase behavior, microstructure, and proton conductivity

AU - Yamazaki, Yoshihiro

AU - Hernandez-Sanchez, Raul

AU - Haile, Sossina M.

PY - 2010/10/7

Y1 - 2010/10/7

N2 - Recent literature indicates that cation non-stoichiometry in proton-conducting perovskite oxides (ABO3) can strongly influence their transport properties. Here we have investigated A-site non-stoichiometry in Ba1-xZr0.8Y0.2O3-δ, a candidate electrolyte material for fuel cell and other electrochemical applications. Synthesis is performed using a chemical solution approach in which the barium deficiency is precisely controlled. The perovskite phase is tolerant to barium deficiency up to x = 0.06 as revealed by X-ray diffraction analysis, but accommodates the non-stoichiometry by incorporation of yttrium on the A-site. The dopant partitioning can explain the decrease in cell constant with increasing x, the decrease in proton conductivity (the latter as measured by a.c. impedance spectroscopy under humidified atmosphere), and the decrease in grain size in the sintered compacts. Within the single-phase region barium deficiency also has a detrimental impact on grain boundary conductivity, as a result both of the decreased grain size, leading to a higher number density of grain boundaries and of an increased per boundary resistivity. At higher values of x, a two phase system is observed, with yttria appearing as the predominant secondary phase and the barium zirconate reverting to an undoped composition. From the relative concentrations of the observed phases and their lattice constants, the ternary phase behavior at 1600°C (the sintering temperature) is generated. Both the bulk and grain boundary conductivities are sharply lower in the two-phase system than in the single phase compositions. The control over processing conditions demonstrates that it is possible to reproducibly prepare large-grained, stoichiometric BaZr0.8Y0.2O 3-δ with a total conductivity of 1 × 10-2 Scm-1 at 450°C, while revealing the mechanisms by which barium deficiency degrades properties.

AB - Recent literature indicates that cation non-stoichiometry in proton-conducting perovskite oxides (ABO3) can strongly influence their transport properties. Here we have investigated A-site non-stoichiometry in Ba1-xZr0.8Y0.2O3-δ, a candidate electrolyte material for fuel cell and other electrochemical applications. Synthesis is performed using a chemical solution approach in which the barium deficiency is precisely controlled. The perovskite phase is tolerant to barium deficiency up to x = 0.06 as revealed by X-ray diffraction analysis, but accommodates the non-stoichiometry by incorporation of yttrium on the A-site. The dopant partitioning can explain the decrease in cell constant with increasing x, the decrease in proton conductivity (the latter as measured by a.c. impedance spectroscopy under humidified atmosphere), and the decrease in grain size in the sintered compacts. Within the single-phase region barium deficiency also has a detrimental impact on grain boundary conductivity, as a result both of the decreased grain size, leading to a higher number density of grain boundaries and of an increased per boundary resistivity. At higher values of x, a two phase system is observed, with yttria appearing as the predominant secondary phase and the barium zirconate reverting to an undoped composition. From the relative concentrations of the observed phases and their lattice constants, the ternary phase behavior at 1600°C (the sintering temperature) is generated. Both the bulk and grain boundary conductivities are sharply lower in the two-phase system than in the single phase compositions. The control over processing conditions demonstrates that it is possible to reproducibly prepare large-grained, stoichiometric BaZr0.8Y0.2O 3-δ with a total conductivity of 1 × 10-2 Scm-1 at 450°C, while revealing the mechanisms by which barium deficiency degrades properties.

UR - http://www.scopus.com/inward/record.url?scp=77956470934&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77956470934&partnerID=8YFLogxK

U2 - 10.1039/c0jm02013c

DO - 10.1039/c0jm02013c

M3 - Article

AN - SCOPUS:77956470934

VL - 20

SP - 8158

EP - 8166

JO - Journal of Materials Chemistry

JF - Journal of Materials Chemistry

SN - 0959-9428

IS - 37

ER -