Conduction properties of Ti‐doped NaTaO3 at intermediate temperature

Abstract

AbstractIn this work, the ionic conductivity and charge carriers of acceptor‐doped sodium tantalate (NaTaO3) with perovskite structure were investigated at intermediate temperatures. The Ta‐site of NaTaO3 was doped with up to 20% titanium (Ti) with the conventional solid‐state reaction method. After calcination at 900°C, samples nominally doped with 5, 10% Ti show X‐ray diffraction (XRD) pattern of orthorhombic NaTaO3 only, while peaks of Na2Ti3O7 can be observed in those doped with 15, 20% Ti. The conductivity of undoped, 5% Ti and 10% Ti‐doped NaTaO3 at 300°C–700°C was measured with electrochemical impedance spectroscopy (EIS) under dry and wet O2 atmospheres. Ti‐doped NaTaO3 samples have higher conductivity in the wet atmosphere than in the dry atmosphere, reaching 3 × 10−4 S/cm at 700°C (10% Ti‐doped NaTaO3), which confirms the hydration and proton conduction in Ti‐doped NaTaO3. Through the investigation on the dependence of conductivity on oxygen partial pressure, hole conduction in an oxidizing atmosphere, and electron conduction in reducing atmosphere can be verified. Na+ conduction was proven to be negligible with direct current polarization.