The Singular Behavior of the Lattice Hardness of Bismuth Cuprates Under Thermocycling

Abstract

AbstractTemperature depepdences of ultrasound velocity V and sound attenuation Q−1,the unit cell parameters a, b, c, and volume W were studied between 77 and 800 K for bismuth cuprates like Bi2Sr2Can−1 CUnO2n+2+8 with n = 1,2,3 (phases: 2201, 2212, and 2223). Acoustic spectra of textured and isotropic samples show anomalies (bending points,extrema, breaks, and splitting of resonance frequency) which are considered as a result of thermostimulated processes - phase transitions of I and II kinds, emergence of substructures in the cuprate lattices - in a system of solid solutions of the mentioned phases. Mechanical properties of the studied systems are observed to be very sensitive to a thermal prehistory (temperature and time ranges of thermocycling).