A study of the dielectric response as a function of frequency (${10}^{2–}$${10}^6$ Hz) and temperature (4.2–300 K) in ceramic and c-axis-oriented single-crystal samples of ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{x}}$ reveals dielectric constants >${10}^3$ at low frequencies in both cases but in different temperature regimes. High-frequency (0.2–20 GHz) measurements of the ceramic sample at room temperature show a loss peak and suggest a relaxation process for the polarization mechanism with characteristic time τ=0.5×${10}^{\mathrm{-}9}$ s, which is near the electrical diffusivity time. For the single crystal the large polarizability results from a thermally activated process with an activation energy of 0.28 eV and an attempt frequency ${\mathrm{\omega }}_0$ of about ${10}^9$ Hz at 300 K. Our results show that the high dielectric constant may be a common feature of the 1:2:3-structure oxide family, and that the previously discovered ordering of the Cu spins at T∼300 K in ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{x}}$ may be accompanied by near ferroelectric polarizability.

• Received 10 November 1992

DOI:https://doi.org/10.1103/PhysRevB.47.8119