Synthesis, properties and ionic conductivity of ceramic solid electrolyte - multicomponent garnet (Y, Ln)3Fe5O12

Abstract

Annotation This paper discusses the synthesis, structure and properties of multicomponent garnet (Y0.2Gd0.2Er0.2Eu0.2Dy0.2)3Fe5O12 obtained by glycine-nitrate pyrolysis and coprecipitation methods ((Y,Ln)IG_pyr and (Y,Ln)IG_ cop samples, respectively). For comparison Ме3Fe5O12 garnets (Ме=Y, Eu, Gd, Dy, Er) were synthesized and studied. According to XRD data the samples have a garnet phase with insignificant content of Fe2O3 or orthoferrites; by Rietveld refinement а distortion of FeO6 octahedra in (Y,Ln)IG_pyr was found. Grains are 1-2 microns in size and round or rod-shaped; the grains form agglomerates. The distribution of Y, Eu, Er, Gd, Dy, Fe in (Y,Ln)IG_pyr grains is more homogeneous than that in (Y,Ln)IG_cop. Absorption bands related to O2- → Fe3+ and d-d transitions of VIFe3+ and IVFe3+ were found in the optical spectra of garnets. The band gaps were estimated to be 2.45 and 2.42 eV for YIG and (Y,Ln)IG_pyr, respectively. Variations in the Raman spectra of garnets were analyzed in the ranges 80 - 300 and 300 - 750 cm-1, associated with translational displacements of Y(Ln)O8 dodecahedra and vibrations of FeO4 tetrahedra, respectively. The Raman data were analyzed using a statistical approach based on the autocorrelation function and the associated parameter Δcorr. An experimental study of the electrochemical impedance was performed. The equivalent circuit method was used to process the impedance spectra. The activation energy Ea was estimated; relaxation processes and dielectric properties of garnets were considered. Electrical conductivity of multicomponent garnet is greater than that of single-component garnet. Multicomponent garnet is characterized by lower activation energies of the electrical conductivity process, and relaxation processes occur in it at lower temperatures. The values of dielectric constants for single-component garnet Y3Fe5O12 are lower than that for multicomponent, which opens up prospects for the use of (Y0.2Gd0.2Er0.2Eu0.2Dy0.2)3Fe5O12 in microelectronics.