Orthorhombic-tetragonal transition in YBa2Cu3Ox

Abstract
Large discrepancies occur between the temperature of the orthorhombic-tetragonal transition determined at high temperatures and that found in samples quenched into mercury from different temperatures. This is because for intermediate x values, samples appear to undergo a non-quenchable transition from tetragonal to orthorhombic during cooling which is not associated with oxygen uptake. Anomalies in the composition dependence of the c lattice parameter occur and may be associated with creation of vacancies in the O(4) sites that separate the copper-oxygen planes and chains.