Electrical transport and thermoelectric properties of Ni-doped perovskite-type YCo1−xNixO₃(0 ≤x≤ 0.07) prepared by sol-gel process

Electrical transport and thermoelectric properties of Ni-doped YCo 1− x Ni x O 3 (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 YCo 1− x Ni x O 3 decrease, but carrier concentration increases. The temperature dependences of the resistivity for YCo 1− x Ni x O 3 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 E a1 in LRT and E a2 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 YCo 1—x Ni x O 3 ( 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 YCo 1− x Ni x O 3 is enhanced remarkably in a temperature range from 300 to 740 K, i.e., a 6-fold increase is achieved at 500 K for YCo 0.98 Ni 0.02 O 3 , indicating that the high-temperature thermoelectric property of YCoO 3 can be improved by partial substitution of Ni for Co.