On Zr substitution in T '-type Nd-Ce-Cu-O system

Abstract

The effect of tetravalent Zr substitution (less than or equal to 2 at%) at the Cu site in T'-type Nd2-xCexCuO4-delta (NCCO), x = 0.12, 0.14, 0.15, on the superconducting (SC) behavior is investigated. EDX analyses of the samples clearly reveal the presence of only similar to 0.5 at% Zr in the T'-phase. Irrespective of the Ce content (0.12 less than or equal to x less than or equal to 0.15), T-c is found to depress with Zr. A fall in T-c of similar to 2 K is observed due to 0.5 at% Zr4+ in x = 0.14 samples, while the NCCO (x = 0.12) on substitution of Zr (expected to dope 2 electrons per Zr4+ and induce superconductivity) remains non-SC. The reported conjecture regarding T-c inducement due to the carrier addition of 0.03 (per formula unit) arising from 3 at% In3+ (or Ga3+) substitution for Cu in Nd1.88Ce0.12CuO4-delta [Ayoub ct al., Physica C170, 211 (1990); Felner et al., Phys. Rev. B40, 11366 (1989)] is not applicable for the Zr-substituted NCCO.