Dielectric relaxation in Yb-doped SrZrO₃

The dielectric constant of the proton conductor SrZr_1-xYb _xO₃ (x = 0-0.1) was measured as a function of temperature and frequency. Two well-defined relaxation peaks were observed in SrZrO ₃ doped with more than 1 mol% of Yb. The assignment of the two dielectric relaxations is discussed in terms of IR spectra and by free energy calculation for a miscibility of dopant Yb ions. The Yb concentration dependence of the relaxation strength of the two dielectric relaxations is in agreement with the results calculated from the free energy. The two relaxations can be assigned to a reorientation of a single Yb-OH dipole and of Yb-OH dipoles associated with Yb-clusters. The attractive energy for Yb-clustering in SrZrO₃ is evaluated at about -85 meV.