Resolving the Pseudogap in theY_xP r_1-xBa₂Cu₃O_7-δ system.

Synthesis of polycrystalline Y_xPr_1−xBa₂Cu₃O_7−δ(0 ≤ x ≤ 0.275, δ ≈ 0) samples has been achieved through solid state reaction. The samples are shown to be nearly single phase by XRD analysis. A recipe that had been used previously for making similar samples was found to yield large and inhomogeneous grain sizes. Improvements on the synthesis led to more homogeneous samples and smaller grain sizes. Samples prepared by both methods were subjected to resistance measurements within the temperature range of 20k and 300k. Samples where lead contacts showed signs of peeling off had relatively low signal to noise ratios with respect to samples for which the contacts were more robust. A linear fit method was used on the latter in order to detect deviations from linearity of resistance vs. temperature data in going from the normal to the superconducting state. Samples prepared using the old recipe did not yield detectable deviations. For the improved samples, the onset temperature of these deviations was marked as the Pseudogap Temperature (T*). The values of T* thus obtained are within the range that our collaborators have found in thin film samples with similar doping amounts. We present an updated phase diagram that includes our results.