Thermal Expansion of Pb2Sr2Y1-xCaxCu3O8+delta

The thermal expansion of Pb2Sr2Y1-xCaxCu3O8+delta has been measured between 25 and 700 degrees C for x = 0, 0.2, and 0.4. Measurements were made on ceramic samples with delta = 0 during heating at 4 degrees C/min in N-2 and O-2 atmospheres. In N-2 the coefficient of thermal expansion is similar to 13 ppm/degrees C for all compositions. In O-2 the expansion varies greatly with temperature as the samples undergo both oxidation and reduction. The expansion mimics previously reported gravimetric data. Two maxima of similar to 1.4% are found near 550 and 700 degrees C. The lattice expansion on oxidation contrasts to the shrinkage observed when Ba2YCu3O6.2 is oxidized.