VARIATION OF HOLE CONCENTRATION INDUCED BY ELEMENT SUBSTITUTION AT Y AND CU(I) SITES IN YBA2CU3OY SYSTEM

Co and Ca may be substituted for Cu (I) and Y in YBa2Cu3Oy compounds. We have studied the effects of these substitutions on the hole concentration, crystal structure, and critical temperature for superconductivity (T(c)). Plausible mechanisms have also been deduced. The hole concentration (P(sh)) in the Cu-0 planes is greatly influenced by both the substituents and the atomic sites. When Co is substituted for Cu(I), P(sh) would decrease because of the filling and the localization of the holes. When Ca substitutes for Y, then P(sh) would increase because of the delocalization of the holes. For double substitutions [Ca and Co for Y and Cu(I) ], hole generation (instead of localization of holes) is important for the variation of P(sh). The relation between P(sh) and T(c) is also discussed.Physics, MultidisciplinarySCI(E)0ARTICLE2297-3031