Resisitivity, thermopower, and susceptibility ofRNiO3(R=La,Pr)

We report the resistivity, thermopower, and dc susceptibility of R${\mathrm{NiO}}_3$ (R=La,Pr) ceramic samples for 1.4 K≤T≤300 K. The resistivity of ${\mathrm{LaNiO}}_3$ shows a ${\mathit{T}}^2$ dependence below 80 K and changes over to a ${\mathit{T}}^{1.5}$ dependence at higher temperature (100–300 K). The resistivity of ${\mathrm{PrNiO}}_3$ exhibits a metal-insulator transition at ${\mathit{T}}_{\mathrm{MI}}$=130 K with a linear temperature dependence above ${\mathit{T}}_{\mathrm{MI}}$. The thermopower of both ${\mathrm{LaNiO}}_3$ and ${\mathrm{PrNiO}}_3$ is linear and negative in the metallic region. The susceptibility of ${\mathrm{LaNiO}}_3$ 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 ${\mathrm{LaNiO}}_{3+\mathrm{\delta }}$, which suggests that the oxygen content of ${\mathrm{LaNiO}}_3$ is important for its physical properties.