Pressure dependence of resistivity for normal‐state ‘‘123’’‐superconducting copper‐oxide compounds

The copper oxides RBa2Cu3O7−δ (R=Y, Pr, Nd) were synthesized, then annealed under 1 atm oxygen. The resistivity was then measured up to pressures of 6.6 GPa for each compound in both as synthesized and oxygen‐annealed conditions. The non‐superconducting, semiconductor, PrBa2Cu3O7−δ, was found to exhibit similar response to the two metallic materials at lower pressures, showing a drop of about an order of magnitude. Above around 2 GPa, however, where the two latter materials continued to show a negative slope with increasing pressure, the Pr‐compound exhibited a positive pressure coefficient.