CHARGE-TRANSFER IN YBA2CU3OX

The charge-transfer hypothesis is shown to be inconsistent with data f or YBa2Cu3Ox: (i) The two-step behavior of T-c(x) (with jumps from zer o to approximate to 60 K and then to approximate to 90 K) is not refle cted as a similar, statistically significant two-step behavior in the bond-valence-sum charge of cuprate-plane Cu ions (as once believed), ( ii) as a consequence of the law of conservation of charge, the derivat ives of the layer charges with respect to oxygen content x for both th e Ba-O layers and the charge-reservoir Cu-O chains have the opposite s igns to those predicted, and (iii) the charge-transfer observed for su perconducting YBa2Cu3Ox is not sufficient to produce superconductivity , as demonstrated by insulating PrBa2Cu3Ox which has virtually the sam e layer charges.