Oxygen behaviour of Yb-doped SrZrO3 at high temperature

Ten mole percent ytterbium-doped SrZrO3, which has the highest proton conductivity among the ytterbium-doped SrZrO3, has been studied by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and differential thermal analysis (DTA) to elucidate the effect of dopant amount of ytterbium ions. The results are compared with those of 5 mol% ytterbium-doped SrZrO3 of our previous work. The orthorhombic unit cell volume increases monotonously with increasing temperature but exhibits a bent between 500 and 600 °C, which is about 300 K lower than that of 5 mol% ytterbium-doped SrZrO3 and then increases again with temperature. This bent of the unit cell volume is considered to be due to a loss of oxygen, which is consistent with the result of a weight loss in TGA observed in the same temperature range. The weight loss and gain on heating and on cooling, respectively, were observed in TGA but do not exhibit so clear hysteresis loop as observed for 5 mol% ytterbium-doped SrZrO3. The displacements of oxide ions were observed in the Fourier syntheses followed by a loss of oxygen at high temperature.