High Total Proton Conductivity in Large-Grained Yttrium-Doped Barium Zirconate

Abstract

Barium zirconate has attracted particular attention among candidate proton conducting electrolyte materials for fuel cells and other electrochemical applications because of its chemical stability, mechanical robustness, and high bulk proton conductivity. Development of electrochemical devices based on this material, however, has been hampered by the high resistance of grain boundaries, and, due to limited grain growth during sintering, the high number density of such boundaries. Here, we demonstrate a fabrication protocol based on the sol-gel synthesis of nanocrystalline precursor materials and reactive sintering that results in large-grained, polycrystalline BaZr 0.8 Y 0.2 O 3-δ of total high conductivity, ∼1 Â 10 -2 Scm -1 at 450 °C. The detrimental role of grain boundaries in these materials is confirmed via a comparison of the conductivities of polycrystalline samples with different grain sizes. Specifically, two samples with grain sizes differing by a factor of 2.3 display essentially identical grain interior conductivities, whereas the total grain boundary conductivities differ by a factor of 2.5-3.2, depending on the temperature (with the larger-grained material displaying higher conductivity).

Comparative Study of BaY0.1Zr0.9O3-δProtective Layers Deposited to BaY0.1Ce0.9O3-δMembrane Using Ultrasonic Spray Pyrolysis and Magnetron Sputtering Methods

“…grain size, internal porosity etc. 19 and changes in Ba stoichiometry in bulk as well as grain boundary region caused by thermal treatment. 20 In this work we prepared thick supportive BaCe 0.9 Y 0.1 O 3-δ membranes using powders from ultrasonic spray pyrolysis method.…”

STRUCTURAL, DIELECTRIC AND A.C. CONDUCTIVITY STUDIES OF BaCe0.65 Zr0.2Y0.15O3-δ SOLID OXIDE FUEL CELL ELECTROLYTE BY CITRATE EDTA COMPLEXING SOL-GEL PROCESS.

“…The conductivity depicted enomorous rise with increase in temperature from ~10 -6 S/cm at room temperature to ~10 -5 S/cm above 300°C . In the present composition as trivalent Y 3+ replaces Ce 4+ , oxygen vacancies are created which in turn trap protons that make defect pairs to aid in the formation of electric dipoles [27].…”

A Study on Sintering Behavior and Conductivity for NiO-doped BaZr0.85Y0.15O3-δ

“…반면에 BaZrO3 는 화학적으로 안정하고 높은 bulk전도도를 보여주 [2][3][4][5][6] . 그러나 1600℃ 이상의 높 은 소결(sintering) 온도가 필요하고, 소결 후 grain 크 기가 1μm 이하로 grain boundary 영역에 의한 전도도 저하가 발생한다 [7][8][9][10] . 또한 고온에서 하소(calcination) 및 소결을 진행하면 Barium(Ba) 증발현상에 의해 Barium Oxide 형태로 변형되어 grain boundaries 에 서 proton의 이동을 방해하게 된다 11) .…”