Investigations on the (thallium,lead,bismuth) strontium(2) copper oxygen(5) superconductors and barium(2-x) potassium(x) lead oxygen(4) oxides

Systematic studies on the chemistry and superconductivity of (Tl,Pb,Bi){dollar}rm Srsb2CuOsb5{dollar} and {dollar}rm Basb{lcub}2-x{rcub}Ksb{lcub}x{rcub}PbOsb4{dollar} oxides have been carried out using solid state reactions, powder x-ray diffraction, DC-resistivity measurements, magnetic susceptibility studies, thermal analysis, x-ray photoemission spectroscopies, etc. The investigations were focused on synthetic methods, solid solution formation, oxygen content, physical and structural properties of high temperature superconducting oxides and their related compounds.; Single phase samples of {dollar}rm Tlsb{lcub}1-x{rcub}Pbsb{lcub}x{rcub}Srsb2CuOsb5{dollar} with {dollar}rm 0.4le xle0.5{dollar} were prepared with tetragonal P4/mmm symmetry. Samples of {dollar}rm Tlsb{lcub}0.5{rcub}Pbsb{lcub}0.5{rcub}Srsb2CuOsb5{dollar} quenched from 850{dollar}spcirc{dollar}C to room temperature are superconducting with {dollar}rm Tsb{lcub}c{rcub}sim 60{dollar} K. Samples of {dollar}rm Tlsb{lcub}0.5{rcub}Pbsb{lcub}0.5{rcub}Srsb2CuOsb5{dollar} quenched from 900{dollar}spcirc{dollar}C into liquid nitrogen are semiconducting, and transform to metallic phases upon annealing in air at 500{dollar}spcirc{dollar}C.; In the {dollar}rm Tlsb{lcub}1-x{rcub}Bisb{lcub}x{rcub}Srsb{lcub}2{rcub}CuOsb5{dollar} system, single phase samples were prepared for {dollar}rm 0.2le xle 0.5{dollar}. Superconductivity with a {dollar}rm Tsb{lcub}c{rcub}sim 45{dollar} K were demonstrated for the first time in samples with {dollar}rm 0.2le xle 0.3{dollar} quenched from 850{dollar}spcirc{dollar}C into liquid nitrogen and then annealed at 400{dollar}spcirc{dollar}C for 1 hour in air or oxygen atmosphere. In the range {dollar}rm 0.2le xle 0.5,{dollar} both semiconducting and metallic phases can be prepared. In general, samples quenched from 850{dollar}spcirc{dollar}C to liquid nitrogen temperature are semiconducting; semiconducting samples annealed in air or oxygen at higher temperatures (from 850{dollar}spcirc{dollar} to 500{dollar}spcirc{dollar}C) and for longer time (from 1.5 to 3.5 hours) yield metallic phases.; Further investigations were carried out on the (Tl,Pb,Bi){dollar}rm Srsb2CuOsb5{dollar} system. Single phase samples of {dollar}rm Tlsb{lcub}0.5{rcub}Pbsb{lcub}0.5-x{rcub}Bisb{lcub}x{rcub}Srsb2CuOsb5{dollar} for {dollar}rm 0.1le xle 0.4{dollar} and {dollar}rm Tlsb{lcub}0.7{rcub}Bisb{lcub}0.3-y{rcub}Pbsb{lcub}y{rcub}Srsb2CuOsb5{dollar} for {dollar}0.1le rm yle 0.2{dollar} can be prepared. The correlations between the composition, oxygen content, structural and electronic transport properties of these compounds are discussed. In (Tl,Pb,Bi){dollar}rm Srsb2CuOsb5,{dollar} the cell parameter variations due to the composition and oxygen content suggest that there could be two types of oxygen deficient sites (i.e., O(1) or O(3)). The nature of the oxygen vacancies are attributed to the magnitude of the cation charge in the (Tl,Pb,Bi)-O plane.; Single phase samples of {dollar}rm Basb{lcub}2-x{rcub}Ksb{lcub}x{rcub}PbOsb{lcub}4-delta{rcub}{dollar} with {dollar}rm 0.1le xle 0.3{dollar} were prepared in Ar atmosphere. The as-prepared samples for {dollar}rm 0.1le xle 0.3{dollar} are oxygen deficient and insulating ({dollar}10sp6{dollar} ohm-cm). The oxygen annealing treatment can increase the oxygen content, leading the insulating samples to become semiconducting. The decrease of resistivity by oxygen annealing is attributed to the formation of peroxide-type oxygen (O{dollar}sb2sp{lcub}2-{rcub}{dollar}) in the structure which was detected by the XPS spectra of O(1s) transitions.