Resisitivity, thermopower, and susceptibility of RNiO3 (R=La,Pr)

We report the resistivity, thermopower, and dc susceptibility of RNiO3 (R=La,Pr) ceramic samples for 1.4 K≤T≤300 K. The resistivity of LaNiO3 shows a T2 dependence below 80 K and changes over to a T1.5 dependence at higher temperature (100-300 K). The resistivity of PrNiO3 exhibits a metal-insulator transition at TMI=130 K with a linear temperature dependence above TMI. The thermopower of both LaNiO3 and PrNiO3 is linear and negative in the metallic region. The susceptibility of LaNiO3 is Pauli-like with a Curie-Weiss contribution at low temperature. The Pauli term is enhanced well above the free-electron value. Our samples have smaller resistivity and larger resistivity ratio than previously reported. Thermogravimetric analysis shows that there is excess oxygen (δ>0) in our samples of LaNiO3+δ, which suggests that the oxygen content of LaNiO3 is important for its physical properties.