ELASTIC BEHAVIOR OF SOME Y-BA-CU-O HIGH T-C SUPERCONDUCTING MATERIALSWITH VARIOUS OXYGEN CONCENTRATIONS

Y-Ba-Cu-O high T-c superconducting materials with various oxygen conce ntrations have been prepared by the solid state reaction method. After characterizing the samples X-ray diffraction, iodometry, density etc. measurements, the ultrasonic velocity studies were also undertaken ov er a temperature range 80-300 K by the pulse transmission technique. I t has been observed that the room-temperature Young's and rigidity mod uli are found to increase continuously with increasing oxygen concentr ation of the samples. A suitable explanation for the observed behaviou r based on Cu(1)-O(4) bond length, oxygen deficiency, copper valency f luctuations etc. is given. Further, it has also been observed from the velocity vs. temperature plots of all the samples that they are found to behave like normal solids, but for the exhibition of a velocity ma ximum in the temperature range 160-210 K, signifying the presence of l attice instabilities. A model based on the readjustment of oxygen atom s among Cu-O planes has been used to explain the observed elastic anom alies.