Study of the structural, optical, and electrical characteristics of Sr2Sn1.6In0.2Cu0.2O6-δ mixed ionic-electronic conductor

Abstract

A solid state route is used to ensure the synthesis of the oxygen-deficient, mixed-valence double perovskite Sr2Sn1.6In0.2Cu0.2O6-δ. This novel mixed ionic-electronic conductor's (MIEC) structural, morphological, optical, and electrical characteristics were investigated. The arrangement of the Sn, In and Cu cations shows discrete tin/copper-oxygen and tin/indium-oxygen layers in a structure characterized as a √2ap x √2ap x 2ap deformed perovskite, and Rietveld refinement of the XRD data reveals a monoclinic phase under P21/c space group. The elemental analysis with EDX permitted the identification of the elemental composition of the sample, and the average grain size as measured with a scanning electron microscope (SEM) is around 230 nm. Sn–O, In–O, and Cu–O vibrations detected by FTIR spectroscopy analysis near 581 cm-1 further confirm the desordered nature of this perovskite structure. The calculated bandgap of 3.35eV reinforcing the semiconducting nature of the sample increases the potential of studied compound as MIEC. The complex impedance spectroscopy technique was employed in the dielectric investigation and electrical conductivity determination of the sample at different temperatures and frequencies. Nyquist diagrams (- Z″ versus Z′) showed a relaxation of the Cole-Cole type that was not Debye-like. The Correlated Barrier Hopping (CBH) model is the suitable to represent the conductivity of the compound, with two separate behaviors beyond and below T = 260 °C. The conductivity dependence vs temperature follows Arrhenius' law in the two just mentioned temperature domains, with activation energies 0.82 and 0.31 eV respectively.