Study of electrical properties of Perovskite (𝐄𝐮 − 𝐒𝐫)𝐓𝐢𝟏−𝐱 𝐗𝐱𝐎𝟑

Abstract

In recent years, there has been an urgent need to develop lead-free Ceramic oxide due to the health hazards of lead (Pb) and environmental issue of concern. Hence, there is a drive to grow environment-friendly ceramic materials to replace traditional lead-in oxide materials. In this regard, the strontium titanate (SrTiO3) (abbreviated as STO) compound is considered as one of the promising materials owing to its superior electric properties and excellent energy application. In addition, the researchers have been able to improve the conductivity of pure SrTiO3 by doping process. Consequently, in the present thesis suitable doping at A and B sites was performed to obtain great performing electrical properties. The manganese-doped europium strontium titanate lead-free ceramic has been successfully prepared by standard solid-state reaction method at high temperatures. The electrical properties of polycrystalline ceramics Eu0.9Sr0.1Ti1-xMnxO3 (where x = 0,0.1, and 0.2) were investigated by means of impedance spectroscopy technique. The effects of Mn doping on the electrical properties were analysed for different doping concentration. The conduction mechanism and impedance spectrum were also comprehensively studied in the temperature range of 300K to 700K over a wide frequency window, 40 Hz to 110 MHz. Complex impedance analysis indicates the presence of a relaxation phenomenon analysis and confirms that the relaxation processes are of the non-Debye type. The impedance spectra for (x=0, 0.1) show a low frequency hook at different temperatures associated with an inductance. The impedance results were fitted by an adequate equivalent circuit involving two contributions attributed to grains and grain boundaries. The electrical measurements prove that the conductivity depends on Mn concentration. The activation energy Ea is elevated from 104 meV to 305 meV when increasing the manganese content. The obtained value of activation energy evidence that the conduction mechanism is thermally activated. Also, Conductivity analysis indicates that the investigated compound exhibits a semiconductor behaviour. It is found that the conductivity spectra of the studied sample follow a single Jonscher‟s Law. Then the thermal evolution of the electrical conduction is explained in terms of the Hopping conduction mechanism. The conduction mechanism over the dispersive region is interpreted by different models. In fact, the variation of the frequency exponent „s‟ with temperature shows distinct hopping mechanisms with different manganese content. These results indicate that the suitable Mn content is beneficial to improve the electrical performances of the material