Depending on the level of oxygen vacancies and temperature, YBa 2 Cu 3 O 7 can be

Depending on the level of oxygen vacancies and temperature, YBa₂Cu₃O_7−δ can be either a (poor) metallic conductor, an antiferromagnetically ordered insulator, or a superconductor. A simplified phase diagram separating the different regions is shown below.

(a) Give a brief description of the structure of YBa₂Cu₃O_7−δ, emphasizing the features relevant for its superconducting properties.

(b) Describe key changes in structural or physical properties of YBa₂Cu₃O_7−δ as you move along each of the arrows 1, 2, and 3 in the figure.

(c) State which characterization techniques would give information on each of the arrowed transitions.

(d) Describe how a material with optimum superconducting properties could be prepared.

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temperature (K) 600 500 400 300 200 100 0 tetragonal orthorhombic 1.0 2 0.5 Sin YBaCu3O 3 0.0