Dielectric relaxation in Yb-doped SrZrO₃

Abstract

The dielectric constant of the proton conductor SrZr1−xYbxO3 (x = 0–0.1) was measured as a function of temperature and frequency. Two well-defined relaxation peaks were observed in SrZrO3 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 isevaluated at about −85 meV.

Reduction in sintering temperature of stable proton conductor BaCe0.35Zr0.5Y0.15O3-δ prepared by sol–gel method and its transport properties

“…The peaks at intermediate and higher frequencies (Fig. 7a), whose intensities are found to increase with temperature, can be attributed to the dipolar loss due to defect association of protons with dopants (Y-H) in the clusters such as [YO 6 ]-[YO 6 ]… and in the isolated octahedra [YO 6 ], respectively [13,17,18]. As the dopant (Y 3+ ) replaces Ce 4+ in the B-site of perovskite-type BCZY, the dopant associates an effective negative charge of − 1.…”

Dielectric relaxation of protonic defects in hydrated and dehydrated SrZrO3:Yb

“…The relaxation in higher frequency side is defined as relaxation 1 (R1), and another in the lower frequency side is defined as relaxation 2 (R2). The two types of dielectric relaxations R1 and R2 were assigned to reorientations of an isolated Yb-proton dipole and of Yb-proton dipoles associated with Yb-cluster, respectively, by free energy calculation for a miscibility of dopant Yb ions [10]. In order to estimate the amount of the protons, IR absorption measurement were carried out for the various Yb concentration samples which were annealed in the WET and DRY atmosphere; the results were shown in Figs.…”

“…The relaxation time τ and relaxation strength Δε were evaluated by nonlinear least-squares fitting with the formula based on Havriliak-Negami form [10,14]. The activation energy E a was estimated by Arrhenius plot of the relaxation time τ against the reciprocal temperature, i.e.…”

“…Dipole relaxations in such oxides were experimentally recognized to exist by dielectric and mechanical relaxation measurements [6][7][8][9][10], indicating that the dopant-proton dipoles will be made locally (i.e. effectively negative charged dopant and positive charged proton).…”

“…effectively negative charged dopant and positive charged proton). Recently, we proposed that there were two types of configurations for the proton-dopant association in SrZrO 3 :Yb [10]. One is the configuration that a proton is associated with an isolated [YbO 6 ]-octahedron, in which "isolated" means that a dopant Yb is octahedrally surrounded by six Zr ions through oxygen.…”