Electrical characterization of porous La-doped BaSnO3 using impedance spectroscopy

A few compositions in the system Ba1 − xLaxSnO3 (x = 0.00, 0.01, 0.05, and 0.10) have been synthesized via the solid state ceramic route. The synthesized powders have been characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, Raman spectroscopy, Fourier transformation infrared, thermogravimetrical analysis, and differential thermal analysis techniques. The powder X-ray diffraction pattern of the samples confirms the formation of a single-phase solid solution only up to 0.50 ≤ x. It was found that all the samples have a cubic crystal structure. The electrical properties of La-modified BaSnO3 were studied using ac impedance spectroscopy technique over a wide range of temperatures (50–650 °C) in the frequency range of 10 Hz–13 MHz. The complex impedance plots above 300 °C show that total impedance is due to the contributions of grain and grain boundaries. The resistance of these contributions has been determined. Variation of these resistances with temperature shows the presence of two different regions with different slopes. The nature of the variation of conductivity of the grain and grain boundaries is different in different regions. Based on the value of activation energy, it is proposed that conduction via hopping of doubly ionized oxygen vacancies (VO••) is taking place in the temperature region of 300–450 °C, whereas in the temperature region of 450–650 °C, it is due to proton, i.e., OH• ions, hopping.