Oxygen nonstoichiometry and electrical properties of La2-xSrxNiO4+δ (0 ≤ x ≤ 0.5)

The amount of interstitial oxygen (delta) in Sr-doped lanthanum nickel oxide (La2-xSrxNiO4+delta) as a function of Sr content has been investigated by the thermogravimetry analysis (TGA) and X-ray photoelectron spectroscopy (XPS). La2-xSrxNiO4+delta (0 <= x <= 0.5) ceramics were prepared by the general solid-state reaction process and sintered in different ambient of argon, air or oxygen, respectively. An increase in the amount of Sr decreased delta in La2-xSrxNiO4+delta, while the Ni2+/Ni3+ ratio analyzed by Ni3p XPS decreased indicating that the oxidation state of Ni increased. Particularly when the sample was sintered in a low oxygen partial pressure condition such as in Ar ambient, the hole concentration strongly depended on the Sr content, suggesting that the hole generation seems mostly originated from Sr2+ substitution into the La3+ site.