Abstract
The electrical behavior of textured YBaCo2O5+δ thin layers (100, 150, and 240 nm) grown on SrTiO3 substrates was investigated by means of complex impedance and transport measurements. Strong dependence of the electrical properties of the layers on the frequency, temperature, and thickness was observed. A semiconducting-like behavior was verified for the investigated films. The impedance spectra (semicircle arcs) were well modeled in terms of equivalent electrical circuits. The circuital analysis allowed for distinguishing between capacitive and resistive contributions to the impedance. The insulating phase and the dielectric relaxation were modeled by means of a conventional resistor-capacitor element connected in parallel. The conductivity data was adequately fit to Jonscher's law, σac = σdc + Aωn. Values of the n exponent lower than 1 were obtained in the temperature range measured. The value of the real part of the dielectric permittivity (ε′r) grew as the temperature was increased and the frequency lowered. An activation energy of ~70 meV was determined from the impedance data. High values of the dielectric loss (tanδ) were observed in the lower frequency region and at the higher temperatures measured. Separate measurements on blank SrTiO3 substrates were also carried out in the present study for comparison.
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