TY - JOUR

T1 - Dependence of and transport properties on the Cu valence (n=2,3) superconductors

AU - Fukuoka, A.

AU - Tokiwa-Yamamoto, A.

AU - Itoh, M.

AU - Usami, R.

AU - Adachi, S.

AU - Tanabe, K.

PY - 1997

Y1 - 1997

N2 - We have determined the oxygen content and the Cu valence by iodometric titiration of single-phase (Formula presented)(Formula presented)(Formula presented)(Formula presented) (n=2,3), Hg-1212 and Hg-1223, superconductors postannealed under various conditions in either a reducing or an oxidizing atmosphere. Their lattice parameters, (Formula presented), resistivity, and the thermoelectric power have been systematically investigated as a function of Cu valence. Hg-1212 exhibits a parabolic or "bell-shaped" relationship between (Formula presented) and the Cu valence similar to that reported for (Formula presented)(Formula presented) (Hg-1201), while only a half of the parabola is observed for Hg-1223. The systematic variations in the resistivity and the thermoelectric power as well as the relationship between (Formula presented) and the Cu valence confirm that the Hg-1223 sample with the highest (Formula presented) of 135 K is almost optimally doped. Both Hg-1212 and Hg-1223 as well as Hg-1201 exhibit their maximum (Formula presented) values at the same nominal Cu valence of approximately 2.20 which is also comparable to those for other high-(Formula presented) cuprate superconductors. This coincidence of the Cu valence for optimally doped states suggests that the simple ionic model where each excess oxygen in the Hg-(Formula presented) charge reservoir supplies two holes is appropriate in the present Hg-12(n-1)n samples.

AB - We have determined the oxygen content and the Cu valence by iodometric titiration of single-phase (Formula presented)(Formula presented)(Formula presented)(Formula presented) (n=2,3), Hg-1212 and Hg-1223, superconductors postannealed under various conditions in either a reducing or an oxidizing atmosphere. Their lattice parameters, (Formula presented), resistivity, and the thermoelectric power have been systematically investigated as a function of Cu valence. Hg-1212 exhibits a parabolic or "bell-shaped" relationship between (Formula presented) and the Cu valence similar to that reported for (Formula presented)(Formula presented) (Hg-1201), while only a half of the parabola is observed for Hg-1223. The systematic variations in the resistivity and the thermoelectric power as well as the relationship between (Formula presented) and the Cu valence confirm that the Hg-1223 sample with the highest (Formula presented) of 135 K is almost optimally doped. Both Hg-1212 and Hg-1223 as well as Hg-1201 exhibit their maximum (Formula presented) values at the same nominal Cu valence of approximately 2.20 which is also comparable to those for other high-(Formula presented) cuprate superconductors. This coincidence of the Cu valence for optimally doped states suggests that the simple ionic model where each excess oxygen in the Hg-(Formula presented) charge reservoir supplies two holes is appropriate in the present Hg-12(n-1)n samples.

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U2 - 10.1103/PhysRevB.55.6612

DO - 10.1103/PhysRevB.55.6612

M3 - Article

AN - SCOPUS:0000156395

VL - 55

SP - 6612

EP - 6620

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 0163-1829

IS - 10

ER -