The effect of annealing time in oxygen flux on the electric properties of the Ru(Sr2−xCax)GdCu2O8±z system with 0.0 < x < 2.0, prepared at ambient pressure

A solid-state reaction method for synthesis of Ru(Sr2−xCax)GdCu2O8±z system within the composition range of 0.0 < x < 2.0, at ambient pressure and within the range of 960-1070 °C is reported. The temperature interval for the preparation of the solid solution is determined by differential thermal analysis (DTA) in air. A solid solution is shown to exist up to x = 0.1, with a crystalline structure that is isomorphous to RuSr2GdCu2O8 (Ru-1212) compound observed by X-ray powder diffraction (XRD). The studies by the scanning electron microscopy (SEM) technique gives a particle size around 1-6 μm. The results of transmission electron microscopy (TEM) studies confirm the tetragonal unit cell of Ru(Sr2−xCax)GdCu2O8±z system. The temperature dependence of the electrical resistivity of the samples annealed in oxygen flux for 12 and 41 h, respectively at T = 960 °C shows a semiconductor behavior.