Grain size effect in La1.85Sr0.15CuO4 superconductor.

M.E. SALETA; C.A. LOPEZ; J. LOHR; R. BENAVIDES; H.E. TOIANI; R.D. SÁNCHEZ

Buenos Aires

Workshop; X Latin American Workshop on Magnetism, Magnetic Materials and their Applications; 2013

The spray pyrolysis technique (SP) is a versatile method to grow dierent kinds of nanogranular oxides, which are ideal systems to study the physics of the interfaces. We can tune the shape of the compound varying carefully dierent synthesis parameters as drop size, deposit rate, pH, atmosphere. In this work we report the synthesis of La1.85Sr0.15CuO4 (LSCuO) by SP. We have optimized the synthesis parameters to obtain two samples with dierent morphologies. Sample A: after microdrops of cation solution were sprayed on a substrate at 1173 K, the sample was thermally treated at the same temperature during 12 h in air atmosphere. Sample B: after spray and dry cation solution, the quasi-amorphous material obtained was pressed in pellets and annealed at 1223 K during 12h. Small amount of diamagnetic impurities have been detected by X-ray diraction in sample B. Scanning and transmission electron microscopies show that sample A is formed by hollow microspheres on top of a granular lm, both of them constituted by crystalline nanograins with structural disorder at the grain boundary. The magnetization vs. temperature curves present superconducting transition with a Tc at 37 K close to the Tbulk c (38K). Electrical transport measurements on sample B evidence a broad superconducting transition. The dierence between Tonset c and TR=0 c is 17 K. This broad transition is a feature of superconductors with micrometer grain size. Finally we present an I-V characterization of a single hollow microsphere (sample A), showing a non-lineal behavior characteristic of the grain boundary barrier.