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In this work we report on the preparation and structural characteristics of good quality superconducting samples of La 2− x Sr x Cu 1− y Zn y O 4− δ ( x = 0.05, 0.08, 0.10, 0.115, 0.15, 0.18, 0.21, 0.25 and y = 0, 0.02) using a wet-chemical method. Previous studies in optimally doped samples prepared with this method demonstrated that the cation distribution inside these samples is improved compared to similar samples obtained by the traditional solid-state method. Since this fact is very important for the study of the superconducting cuprates because their physical properties are strongly correlated with the microstructure and chemical homogeneity, we have extended this wet-chemical method to produce polycrystalline samples with strontium concentrations of interest to superconductivity. In particular, compounds with strontium doping as low as x = 0.05 and 0.08, located at the onset of superconductivity (underdoped region), up to dopant concentrations situated in the highly overdoped region ( x = 0.25) were prepared and characterized. X-ray diffraction measurements and subsequent Rietveld analysis were used to identify the principal lattice parameters of the samples and their doping dependence. Zero field cooling magnetization and resistivity measurements allowed following the critical temperature as a function of the charge carrier concentration. Our experimental results obtained here are compared to others reported on similar La 2− x Sr x CuO 4− δ samples showing that good quality single-phase polycrystalline samples, with several carrier concentrations, can be obtained using the wet-chemical method explored here. |
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