Instability of Y-Ba-Cu-O crystal lattice in temperature range of 5-300 K by thermal expansion data

Coefficient of linear thermal expansion α (LTEC) of cast polycrystal and sintered samples of superconducting Y-Ba-Cu-O ceramics (1-2-3) with Tc ∼ 92 K in 5-300 K jtemperature interval is investigated. At ∼ 40, 80, 120 and 210 K giant LTEC features are manifested in all samples; at T ∼ Tc α features are absent. Curve non-coincidences detected α =f(T) under cooling and heating and the presence of α features point out to an instability of Y-Ba-Cu-O lattice