Insights on thermal and transport features of BaCe0.8−xZrxY0.2O3−δ proton-conducting materials

Abstract

BaCe0.8−xZrxY0.2O3−δ-based materials (BCZYx, 0 ≤ x ≤ 0.8) are obtained through a modified citrate-nitrate combustion method at 1150 °C with following sintering at 1450 °C. Then their thermomechanical and electrical properties are thoroughly investigated. Using of wet-chemical route it is allowed to obtain single-phase and dense ceramic samples at a wide range of Ce:Zr ratio. It is found that the relative linear expansion of ceramics decreased with gradual increasing x, which is reflected in a corresponding drop of thermal expansion coefficient (TEC) values, from 11.6 × 10−6 to 8.3 × 10−6 K−1 (∼30%). It is also found that, the decrease in pO2 does not significantly change the ceramics' linear expansion, whereas the increase in pH2O resulted in marked variation of both linear expansion and TEC values. The electrical conductivity of BCZYx decreases from 0.85 to 0.02 mS cm−1 at 300 °C (∼98%) and from 69.9 to 17.9 mS cm−1 at 900 °C (∼75%) with the increase of x. At the same time, hole contribution on total conductivity increases with increasing x. Taking into account the phase stability in BaCe0.8−xZrxY0.2O3−δ system, the material with optimal properties should be sought at close concentration of Ce and Zr.