Charge and mass transport properties of La2Ni0.95Al0.05O4.025+δ

In this work, mass and charge transport properties of acceptor doped lanthanum nickelate, La2Ni0.95Al0.05O4.025+δ (LNAO), were analyzed. The thermal expansion, electrical conductivity and thermoelectric power of LNAO were measured as a function of temperature in 25-1000 °C range and oxygen partial pressure (pO2) in −14 ⩽ log (pO2/atm) ⩽ −1 range. The average thermal expansion coefficient was 13.77 × 10−6 K−1. The electrical conductivity was analyzed in relation to the thermoelectric power to elucidate the positive deviation of the activity coefficient of hole on the basis of the delocalized electron model. The thermoelectric power measurement shows a p-type to n-type transition. The chemical diffusion coefficient (D̃chem) and surface exchange coefficient (ksurf.) were calculated by 4-probe DC conductivity measurement and ksurf. was slightly higher than (D̃chem). The best-estimated hole-mobility values showed very weak temperature dependence. The results were compared with the literature results on La2NiO4+δ.