Structure/property Relationships in Oxides Containing Copper.

This dissertation is a study of the relationship between the copper valence state and the structure/properties of copper oxides. The temperature dependence of intersite cation migration, oxidation and the Jahn-Teller tetragonal distortion at B-site Cu^{2+} ions in copper ferrospinel were monitored and correlated with anomalies in physical properties reported in the literature. The compounds Cu_{1-x} Fe _{x} Ni_{x} M_ {2-x} O_4 (M = Cr,Rh) (0 <=q x<=q1) were prepared and examined for the competition between Jahn-Teller and spin -orbit distortions induced by A-site Cu^ {2+} ions. The rm Ni_ {x} Mn_{3-x} O_4^inel system exhibits unusual properties associated with the presence of a Mn^{3+} Jahn-Teller ion; it was also studied for comparison. CuO_2 sheets doped with electrons/holes are the critical structural component of cuprate superconductors. Several other factors are also important: for example, electron doping--but not hole doping --of the CuO_2 sheets is found where the copper has fourfold, square-coplanar coordination; hole doping--but not electron doping--is possible where the copper of the CuO_2 sheets has fivefold or sixfold coordination. The suppression of T _{rm c} by Pr in p-type PrBa_2Cu_3 O_{rm 6+x} could be interpreted as due to the hybridization of the Pr:4f^2<=vel and the sigma *_{x^2-y^2 } band states of the CuO_2 sheets. The hybridization was shown to be modulated by the internal electric fields. The structure/property relationships of the system rm La_{2-y} M_{1+y^-} Cu_2 O_ {6+x} (M = Ca, Sr, Ba) were investigated. Lack of superconductivity in spite of the existence of highly hole-doped CuO_2 sheets in the case of the Sr and Ba compounds was shown to correlate with interstitial oxygen atoms, which perturb the conduction band. The properties of the three-dimensional metallic compounds rm La_{4-x} R _{x} BaCu_5 O_{13} and the one-dimensional compounds rm Li_2 CuO_2 and MCuO_2 (M = an alkali metal) as well as other nonsuperconducting two-dimentional compounds were explored. Factors that distinguish the superconductors from the non-superconductors are pointed out. Several new copper oxides were synthesized and characterized, including rm LiCuO_2 , Sr_{5-x} Pb_{3+x} Cu _{y} O_{12-delta}, Gd_{0.5} Sr_{1.5}CuO _{3.53}, Gd_{1.2} Sr_ {1.8} Cu_2 O_{6-delta } and rm Gd_{1+x } Ca_{2-x}Cu_3 O_{6+y }.