HYSTERETIC EFFECT OF SOUND-VELOCITY IN SINTERED BI2SR2CACU2O8+DELTA WITH EXCESS OXYGEN

To explore the relationships between a thermal hysteretic effect of so und velocity and excess oxygens, the temperature dependence of the sou nd velocity in sintered Bi2Sr2CaCu2O8+delta has been measured. To vary the oxygen content, samples have been annealed in different atmospher es (nitrogen, air, oxygen) and then furnace-cooled to room temperature or quenched in liquid nitrogen. The thermal hysteresis has been obser ved only in the quenched samples but not in furnace-cooled samples. It is shown that this hysteresis is related to both the excess oxygen co ntent and the quenching process.