Thermal expansion measurements using x-ray powder diffraction of Tl-1223 substituted by molybdenum

Abstract

Lattice parameters and the volume thermal expansion coefficient, from room temperature down to 80 K, have been calculated for TlBa2Ca2Cu3−xMoxO9−δ with x = 0.0, 0.05, 0.1 and 0.2 using x-ray powder diffraction. The superconducting transition temperature for the prepared samples, determined from electrical resistivity measurements, is suppressed from 122 to 98 K as the Mo content increases from 0.0 to 0.2. This suppression is discussed in terms of the uniaxial pressure induced by the changing of the Jahn–Teller effect and the hole-filling mechanism. The lattice parameters a and c contract with decreasing temperature and the rate of contraction of the lattice parameter a (a80/a300 = 0.9997) is lower than that of c (c80/c300 = 0.9967). The volume thermal expansion coefficient increases from 4.6 × 10−5 to 6.04 × 10−5 K−1 as x increases from 0.0 to 0.2. The Debye temperature, calculated from volume thermal expansion coefficient measurements, is reported as a function of Mo content and superconducting transition temperature and it agrees with that determined from specific heat measurements.

Thermal expansion measurements of (Cu0.25Tl0.75)-1234 added by MgO-nano particles

“…This shift in (1 1 0) plane leads to an increase in the lattice parameter a with increasing temperature. The position of patterns does not have any drastic change in this temperature range, indicating the maintenance of the tetragonal structure of (Cu, Tl)-1234 phase down to 80 K. These results are consistent with those obtained by Hasegawa et al [5] in Tl-2223 phase and Awad et al [10] in TlBa 2 Ca 2 Cu 3−x Mo x O 9−ı .…”

“…Also, the ratios a 80 /a 290 and c 80 /c 290 were estimated for all samples and found to be 0.9963 and 0.9965, respectively. These results are in contrast with those obtained by Awad et al [10] in TlBa 2 Ca 2 Cu 3−x Mo x O 9−ı , which showed that the contraction in the lattice parameter a is less than that of c. This contrast may be due to the fact that the anisotropy parameter of (Cu, Tl)-1234 is lower than that of Tl-1223.…”

“…They found that the lattice parameters increased with temperature, while decreased with oxygen-content. Awad et al [10] reported the variation of the lattice parameters and the volume thermal expansion coefficient, from room temperature down to 80 K, for TlBa 2 Ca 2 Cu 3−x Mo x O 9−ı with x = 0.0, 0.05, 0.1 and 0.2 using X-ray powder diffraction technique. Their work showed that the volume thermal expansion coefficient was increased from 4.6 × 10 −5 K −1 to 6.04 × 10 −5 K −1 as x was increased from 0.0 to 0.2.…”

Superconducting properties of zinc substitution in Tl-2223 phase

“…All the samples have a metallic behavior at high temperature followed by a superconducting transition. The metallic behavior, linear relation above T c , reflects the spin charge separation in CuO 2 -planes results in the longitudinal transport relaxation rate 1/τ ∼ T that gives the well-known linear resistivity in high-temperature superconductivity [4]. A small curvature in the electrical resistivity appears above the superconducting transition temperature that characterizes the superconducting Cooper-pairs fluctuations [17].…”

“…The 3d-transition elements, such as Fe, Co, Zn, Ni and Mo affect the high-temperature superconductors through structure defects and changes in oxygen-content and in carrier concentration at the CuO 2 -planes producing a sensitive variation in the superconducting transition temperature [1][2][3][4]. The effect of zinc in high-temperature superconductors is strongly dependent on the entering site in CuO 2 -planes.…”