Relationship Between Optical Dielectric Constant and Ionic Activation Energy in Perovskite-Type Proton Conductors BaCe_1-xM_xO₃(M = Nd and Gd )

Abstract

To investigate the correlation between the activation energy E ac and electronic structure near the band gap for impurity-type H + -ion conductors, we measured infrared reflectivity spectra of sintered BaCe 1-x M x O 3 (x=0, 0.10, 0.15 for M=Nd and x=0.05, 0.1 for M= Gd) at room temperature, and estimated optical dielectric constant and the phonon frequencies of LO-and TO-modes with Kramers-Kronig analysis. We found a clear proportionality represented as E ac -0.14=[1/( -1.4)]. The proportional form is shifted from that of superionic conductor. For the origin of the shift, we attribute weakened influence of the Coulomb force of the host lattice on mobile H + -ion. This mechanism is confirmed from the volume and mass dependences of E ac values, and also from reasonable interpretation about smaller E ac value of AB 1-x M x O 3 than that of ABO 3 with respect to the impurity electronic levels near the band edge.

Experimental neutron scattering evidence for proton polaron in hydrated metal oxide proton conductors

“…It may clarify the difference of parabolic and linear relations of vibration frequency on E a . Strong contribution of electronic polarizability on E a is obvious from the relationship between optical dielectric constant and E a values as seen in references 33 36 .…”