ULTRASONIC ANOMALIES AND PHASE-TRANSITIONS IN THE Y1BA2CU4O8 AND THE Y1-XCAXBA2CU4O8 SYSTEMS

Ultrasonic and specific heat measurements have been performed on singl e-phase Y1Ba2Cu4O8 (Y1:2:4) and Y1-xCaxBa2Cu4O8 with x=0.1. In the tem perature range from 65 K to 320 K several anomalies were recorded. Amo ng these were a pronounced elastic anomaly near 260 K in the pure Y1:2 :4, a phase transition at 150 K seen both in specific heat and in elas tic behavior, and another phase transition at 81 K in x=0.1 substitute d material. Thermal hystereses below 200 K were also studied.