Abstract

This study aims to investigate the strong correlation effect of spin and charge carriers for the Mg²⁺-substituted into Cr³⁺ sites of CuCrO2 delafossite on thermoelectric properties. The CuCr0.98Mg0.02O2 sample was synthesized by a solid state reaction. The starting powder CuO, Cr2O3 and MgO were ball milled with poly vinyl alcohol solution for 24 h. The ball milled powder was pressed and sintered in air atmosphere at temperature 1050 C for 6 h. The crystal structure was characterized by XRD, TGA, XPS and the thermoelectric properties were measured at high temperature. The XRD displayed peaks of the pure phase CuCrO2 structure as hexagonal delafossite-type structure space group: Rm. The Seebeck coefficient of the samples displayed positive sign as p-type (hole) conductor. The XPS results displayed Mg²⁺, Cu¹⁺, Cr³⁺ and Cr⁴⁺ ion states. The Mg²⁺ induced mixed-valance Cr³⁺/Cr⁴⁺ states resulting in enhanced Seebeck coefficient due to a strong correlation of the spin-entropy. The experimental results of Seebeck value were close to calculated results by the extended Heikes formula confirming of the strong correlation effect. In addition, the Mg-doped CuCrO2 resulted in increased electrical conductivity and reduced thermal conductivity with increasing temperature. These indicate that the Mg²⁺-substituted for Cr³⁺ of CuCrO2 delafossite enhance the thermoelectric properties. © 2015