Superconductivity and valence states of Ce, Pr and Tb in bulk Lu1−xMxBa2Cu3O7−δ (M = Ce, Pr and Tb) systems

✍ Scribed by K.I. Gnanasekar; A.S. Tamhane; R. Pinto; R. Nagarajan; M. Sharon; L.C. Gupta; R. Vijayaraghavan

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 614 KB
• Volume: 219
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(94)90032-9

✦ Synopsis

Bulk samples of composition Lut_xMxBa2Cu3OT_s (M=Ce, Pr and Tb) are examined with respect to the formation of 1-2-3 phase and the superconducting properties. Samples with M=Pr and Tb form a superconducting 1-2-3 phase for values of x<0.6. We observe that in case of M-: Tb, the zero-resistance transition temperature, Tc¢0), is 85-86 K and independent ofx for 0.1 < x < 0.3. For M=Pr, a maximum Tcco) of 86 K is observed for x=0.1. Tc¢o) decreases with increasing x for x>0.1 and the sample with x=0.6 is observed to be semiconducting down to 12 IC With M=Ce, samples of the composition Lu~_x_yCexCa~Ba2Cu3OT_8 form the superconducting 1-2-3 phase for x, y=0.1 and 0.15. Samples of the compositions Lul_x_~Pr~?,avBa2Cu3OT_8 with x=0.1, 0.2, 0.3 and y--0.1, have lower Tc¢o)'S than samples of a corresponding Pr content without Ca. We infer from our studies that the Pr ions are in the 3+ valence state for 0.1 <x<0.3, the Tb ions are mainly in the 3+ valence state for 0.1 <x<0.3, and the Ce ions are in the 4 + state.