Structural and physical properties of the (Ca, Mg)-doped delafossite powder CuGaO2

We have studied crystal structure of delafossite-type oxide CuGa1−x(Ca,Mg)xO2 (0 ≤ x ≤ 0.04). There is no significant difference in the lattice parameter among the Mg-doped samples and CuGaO2. Contrarily to the Ca-doped samples, there is an important variation in the two lattice parameters a and c because of the big substitution of biunique radius of Ca2+(rCa2+=1 Å)(rCa2+=1 Å). Magnetic susceptibility measurements show that the absence of interactions is antiferromagnetic (AFM). The dielectric conductivity behavior of Ca-doped CuGaO2 delafossite has a tendency to a semicircular at temperature above 573 K. The characteristic activation energy of the conductive processes, which is calculated from the Arrhenius law, is reported to be 0.3 eV for CuGa0.98Ca0.02O2 and 0.57 eV for CuGaO2 samples.

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► Relaxation of the rhombohedral distortion of the GaO6 octahedra.
► A weight gain between 700 °C and 800 °C.
► Ca/Mg introduced into Ga layers blurs the nonmagnetic transition.
► Decrease for value of activation energy.