Preparation and conductive properties of CaHf1−xInxO3−δ

Abstract

Doped CaZrO3 oxides exhibit high proton transport number and have been used in electrochemical hydrogen sensor to measure hydrogen content in aluminum melt. Ionic radius of Hf4+ is close to that of Zr4+; thus, it is speculated that doped CaHfO3 oxides may also possess high proton transport number. In this study, CaHf1−xInxO3−δ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) perovskite oxides were fabricated via solid-state reaction method. Phase composition and microstructure were characterized by X-ray diffraction and field emission scanning electron microscopy. Conductivities and transport properties of CaHf1−xInxO3−δ were investigated via defect equilibria model. The result indicated that conductivities and transport properties of CaHf1−xInxO3−δ after In doping could be improved. Moreover, conductivities increased with increasing In doping content until the stoichiometric ratio of Indium element was 0.1. CaHf0.9In0.1O2.95 showed the highest total conductivities of 5.58 × 10−8 to 7.04 × 10−3 S ⋅ cm−1 at 400–800 °C. Transport properties showed that CaHf1−xInxO3−δ (x = 0.1, 0.15, 0.2, 0.25) oxides were dominated by protonic conduction under 21% O2 and 2.5% H2O atmosphere at 400–650 °C, and the proton transport numbers of CaHf1−xInxO3−δ decreased with the increase in temperature in the range of 400–800 °C. CaHf0.9In0.1O2.95 (x = 0.1) displayed a maximum proton transport number of 0.50 at 800 °C. These findings show potential application prospects of CaHf1−xInxO3−δ in electrochemical hydrogen sensor.