Electrical transport and thermoelectric properties of Ni-doped perovskite-type YCo1−x NixO3 (0 ≤ x ≤ 0.07) prepared by sol-gel process

Abstract

Electrical transport and thermoelectric properties of Ni-doped YCo1−xNixO3(0 ≤ x ≤ 0.07), prepared by using the sol-gel process, are investigated in a temperature range from 100 to 780 K. The results show that with the increase of Ni doping content, the values of DC resistivity of YCo1−xNixO3 decrease, but carrier concentration increases. The temperature dependences of the resistivity for YCo1−xNixO3 are found to follow a relation of ln ρ ∝ 1/T in a low-temperature range (LTR) (T < ∼ 304 K for x = 0; ∼ 230 K < T < ∼ 500 K for x = 0.02, 0.05, and 0.07) and high-temperature range (HTR) (T > ∼ 655 K for all compounds), respectively. The estimated apparent activation energies for conduction Ea1 in LRT and Ea2 in HTR are both found to decrease monotonically with doping content increasing. At very low temperatures (T < ∼230 K), Mott's law is observed for YCo1—xNixO3 (x ≥ 0.02), indicating that considerable localized states form in the heavy doping compounds. Although the Seebeck coefficient of the compound decreases after Ni doping, the power factor of YCo1−xNixO3 is enhanced remarkably in a temperature range from 300 to 740 K, i.e., a 6-fold increase is achieved at 500 K for YCo0.98Ni0.02O3, indicating that the high-temperature thermoelectric property of YCoO3 can be improved by partial substitution of Ni for Co.