Impedance spectroscopic and dielectric analysis of Ba0.7Sr0.3TiO3 thin films

Polycrystalline Ba0.7Sr0.3TiO3 thin film with Pt/BST/Pt/TiO2/SiO2 structure was prepared by ion beam sputtering. The film was post annealed at 700 °C. The dielectric and electric modulus properties were studied by impedance spectroscopy over a wide frequency range [0.1–105 Hz] at different temperatures [175–350 °C]. The Nyquist plots (Z″ vs . Z′) show the contribution of both grain and grain boundaries at higher temperature on the electric response of BST thin films. Moreover, the resistance of grains decreases with the rise in temperature and the material exhibits a negative temperature coefficient of resistance. The electric modulus plot indicates the non-Debye type of dielectric relaxation. The values of the activation energy computed from both plots of Z″ and M″ are 0.86 eV and 0.81 eV respectively, which reveals that the species responsible for conduction are the same. The scaling behavior of M″/M″maxM″/M″max shows the temperature independent nature of relaxation time. The plot of normalized complex dielectric modulus and impedance as a function of frequency exhibits both short and long-range conduction in the film.

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► The material exhibits the contribution of both grain and grain boundaries in the electric response of Ba0.7Sr0.3TiO3.
► The plot of normalized complex dielectric modulus and impedance as a function of frequency exhibits both short and long-range conduction in the film.
► The frequency dependence of ac conductivity exhibits a polaron hopping mechanism with activation energy of 0.38 eV.
► The complex dielectric modulus analysis confirmed the presence of a non-Debye type of conductivity relaxation deduced from the KWW function.