Thermal expansion of Y 2Ba 4Cu 7O 15 in the temperature range 10–290 K, and comparison with YBa 2Cu 3O 7 and YBa 2Cu 4O 8

Abstract

The orthorhombic lattice parameters of superconducting Y 2Ba 4Cu 7O 15.28 ( T c = 85.5 K) are measured as a function of temperature (10–290 K) to a precision of 1 × 10 -4 on a low-temperature Guinier X-ray powder diffractometer by using an internal standard. The thermal expansion is anisotropic (( a 297 K− a 10 K)/ a 297 K = 17(2) × 10 -4, ( b 297 K− b 10 K)/ b 297 K = 11(2) × 10 -4, ( c 297 K− c 10 K)/ c 297 K = 34(2) × 10 -4) and intermediate between that of structurally related YBa 2Cu 3O 7 and YBa 2Cu 4O 8. It is attributed to anharmonic thermal vibrations of the CuO 2-planes and CuO single- and double-chains in the directions of vacant oxygen sites. No anomalous changes as a function of temperature are found within experimental resolution.