High-temperature superconductivity in bismuth-copper oxides of the type Bi m M n Cu p O x (M=Mg, Ca, Sr, Ba, Bi) (original) (raw)
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High-Tc Superconductivity in Cu Oxides
Several findings in the area of copper oxide high-Tc superconductivity are shown; from the first high-Tc cuprate superconductor at 30 k, to a Barium-Itrium-doped cuprate superconducting at around 90 K. The main structure of said compound and the systematic analysis for each one are explained and the preparation methods for some of them are exposed. Finally, the theories attempting to describe the superconducting behavior at said temperatures are examined and briefly explained.
Journal of Physics: Condensed Matter, 1989
We have made four-probe conductivity, AC susceptibility and x-ray diffraction measurements on the following compounds: nine compositions of BiCa,-,Sr,Cu,O, with 0.1 s x < 1, four samples of BiCaSrCuzOz with variations in the ambient and in heat treatment, and the samples with the starting compositions BiCal zjSro 7jCuzOp, Bi,CaSrCu20, and Bi2Caz,,,Sro 7sCuz0,. Many of these Bi-containing compounds exhibit superconductivity around 80 K. Sharp drops in resistivity near 120 K have also been observed in a few cases. The dependence of T, on starting stoichiometry, synthesis conditions and structural parameters are discussed.
Superconductivity in the 70K range in Ca-free Pb_Sr_R_Cu_O oxide system
Solid State Communications, 1990
High temperature bulk superconductivity is well established in several families of copper oxide based systems [1-41, such as, (La,M)2CuO 4, LnBa2Cu307_ 8 and (T1,Bi)m(Ba, Sr)2Can_ 1CunOm+2n+2. More recently, a new family of compounds with general formula Pb2Sr2ACu308+ 8 was reported by Cava et al [5] and confirmed by Subramaniam et al [6]
Solid State Communications, 1987
Compounds of the form (Ml_xM$2Cu04_b and related compounds where M and M' are Y, various rare earths from La to Lu, and the alkaline earths Sr and Ba, have been investigated in connection with high temperature superconductivity. High temperature super conductivity is confirmed for the system (Lal_xBa,)2Cu04_b, (Lal_xSrx)2Cu04_6 and (Yl_,Ba,)2Cu04_b with superconducting transition temperature T, onsets of 30 K, 38 K and 90 K, respectively. We have found that the related systems (Eul_xBax)2Cu04_5 and (Sm1_xBax)2Cu04_g also exhibit high temperature superconductivity with T, onsets of 95 K and 65 K, respectively. The highest T, onset observed in this investigation was 97 K for a sample with the nominal composition of the spine1 StrUCtUre Y. 33Ba0.67 CU204_6. Measurements of the specific heat C as a function of temperature T on a Lao. 8Sr0 2Cu04_ 6 sample reveal a break in slope in the C/T vs T curve at thk T, midpoint, but no clearly discernable jump in C at T,. A linear term _ Y'T in C was observed at low temperature in the superconducting state.
Crystal chemistry and superconductivity of the copper oxides
Journal of Solid State Chemistry, 1990
simplest system Lar.+k,CuO~ (Ln = lanthanide) depending upon the size of Ln and the value ofy. The internal electric field created by the formal charges in the adjacent layers modulates the distribution of holes between the active and inactive layers and the influence of Pr on superconductivity. The coordination geometry preferred by different oxidation states of Cu appears to control the oxygen ordering and the T, variation in the YBa&Or,+, y s stem. The c-axis Cu-0 distance modulates the width of the conduction band and the electronic properties. Chemical characterization of the thallium cuprates has demonstrated that the oxidation of the Tlr-,BarCa,-IC~n02n+4-x s stem can be due to either solely an overlap y of the Tl : 6s band with the conduction band or solely Tl vacancies, depending upon the value of y; as normally prepared, both effects are operative.
Superconductivity in the ‘triple-fluorite-layer’ copper oxides (Cu,M)-1232 (M=Mo, W, Re, Pb)
Solid State Communications, 2006
Here two new high-T c superconductors are reported of the (Cu,M)-1232 structure containing a fluorite-structured (Ce,Y)-O 2-(Ce,Y)-O 2-(Ce,Y) triple-layer block between two adjacent superconductive CuO 2 planes. The new superconductors were found through substitution studies at the Mo site in the recently synthesized superconductor, (Cu 0.75 Mo 0.25)Sr 2 (Ce 0.67 Y 0.33) 3 Cu 2 O 11Cd or (Cu 0.75 Mo 0.25)-1232 [Y. Morita, T. Nagai, Y. Matsui, H. Yamauchi, M. Karppinen, Phys. Rev. B 70 (2004) 174515. [10a]]. Essentially single-phase samples of the (Cu 0.75 M 0.25)-1232 phase with MZW, Re and Pb were obtained by an ambient-pressure solid-state synthesis method. Through a subsequent high-pressure oxygenation (HPO) treatment carried out at 5 GPa and 500 8C in the presence of Ag 2 O 2 as an oxygen source the MZW and Re samples were successfully 'superconductorized'. Introduction of Pb was found to markedly enhance the speed of the formation of the 1232 phase, but the (Cu,Pb)-1232 samples did not exhibit superconductivity. Among the superconductive (Cu,M)-1232 samples, the highest T c value of 56 K was achieved for (Cu 0.75 Re 0.25)-1232. It is likely that the higher the average valence of cations in the (Cu,M)O 1Cd charge-reservoir is, the more can the phase accommodate excess oxygen upon HPO treatment and the higher is the resulting T c value.
The confirmation of superconductivity in the Bi_Sr_Ca_Cu_O system
Solid State Communications, 1988
By exploring more than 30 compositions in a quaternary oxide system BiSrCaCuO, we have (1) confirmed the existance of superconductivity up to 114K and (2) located the composition range for the superconducting phase. Several compositions in the proximity of the BiSrCaCu compositions 6:5:3:6 and 2:2:1:2 revealed identical diffraction patterns, indicating a broad homogeneity range for the superconducting phase. The equilibrium phase exhibits a TC ∼ 86K. Depending upon the heat treatment conditions, multiple superconducting transitions at temperatures above and below 86K have been observed.
Magnetic and transport properties of some Ln-Ba-Cu-O (Ln=Yb, Tm, Sm) superconducting oxides
Solid State Communications, 1987
Powders of Yb-Ba-Cu-0, Tm-Ba-Cu-0 and Sm-Ba-Cu-0 have been synthetized. Electrical resistivity and magnetic susceptibility measurements show that they am superconducting with onset transition temperatures in the range 91 K -85 K. The thermopower, in these oxides as well as in SrxLa2_xCuO4.g and Ba2YCu307_6, is found to be positive