Figure 5.

Temperature dependence of a) the real part ${\epsilon }_{\mathbf{c}}^{\prime }$ and b) the imaginary part ${\epsilon }_{\mathbf{c}}^{\prime \prime }$ of the dielectric permittivity at various frequencies. The relaxations R1 and R2 are indicated by a broad maximum and a sharp peak in ${\epsilon }_c^{\prime \prime }(T)$. c) Pyroelectric currents density divided by the heating rate q for different heating rates. The crystal was cooled under an electric field of E = 3.2 kV cm⁻¹ along the c axis. d) Temperature dependence of the f _R1 and f _R2 relaxation frequencies obtained as positions of maxima from either ${\epsilon }_{\mathbf{c}}^{\prime \prime }(f)$ measured at a particular temperature or ${\epsilon }_{\mathbf{c}}^{\prime \prime }(T)$ spectra measured at a particular frequency. The lines are two Arrhenius fits.