Systematic induction of superconductivity in Y1-xCaxBa2Cu3O6.3 system

TL;DR

This study demonstrates that substituting calcium into YBa2Cu3O6.3 induces superconductivity, with transition temperatures increasing as calcium content rises, and provides insights into the phase diagram of these compounds.

Contribution

It systematically investigates calcium substitution effects on YBa2Cu3O6.3, revealing the induction and enhancement of superconductivity and contributing to the phase diagram understanding.

Findings

Superconductivity onset at x=0.10 with Tconset ~42 K.

Zero resistance achieved at higher x with TcR up to 35 K.

Magneto-transport shows transition broadening under magnetic fields.

Abstract

Compounds of series YBa2Cu3O7-d (d = 0.7), being synthesized by solid-state synthesis route with x = 0.0, 0.10, 0.15 and 0.20, crystallize in single-phase form with tetragonal structure (space group P4/mmm). The c-lattice parameter increases with increasing x, indicating successful substitution of Y3+ by bigger Ca2+ ion. Resistance versus temperature (R vs. T) measurements show that pristine sample (x = 0.0) is semiconducting down to 5 K. Induction of superconductivity is seen with an increase in x. The x = 0.10 sample exhibit the onset of superconducting transition (Tconset) at around 42 K without attaining zero resistance superconducting transition temperature (TcR=0) state down to 5 K. For x = 0.15 and 0.20 samples TcR=0 is observed at 25 K and 35 K with Tconset of 52 K and 61 K respectively. Thermo-electric power (S) measurements in temperature range of 5 - 300 K, exhibited TcS=0 at around 25 K and 35 K respectively for x = 0.15 and 0.20 samples. Further a sign change in S from +ve to -ve is observed at low temperatures for x = 0.0 sample. Room temperature +ve S value decreases with increase in x, indicating enhanced number of mobile holes. The Magneto-transport measurements under applied magnet ic fields of 3 and 6 Tesla show the broadening of superconducting transition for x = 0.15, and 0.20 samples. For x = 0.10 sample the superconducting transition is suppressed in applied fields of 3 and 6 Tesla. Our results will help in constructing the complete phase diagram of Y1-xCaxBa2Cu3O7-d compounds with various x and d.