Impedance Spectroscopy and Temperature Dependent Structural Properties of La-Doped Bi1.5Zn0.92Nb1.5O6.92 Pyrochlore Ceramics رسالة ماجستير

Abstract

In this work, we explored some smart properties of the lanthanum doped Bi1.5-XLaXZn0.92Nb1.5O6.92 (La-BZN) pyrochlore ceramics. This was done because there are known applications for BZN high dielectric material. In this study, the La content denoted by (X) was varied in the range from 0.10 to 0.22. By increasing the La content from 0.10 to 0.20, a single phase appeared where the grain sizes increased from 33 to 57 nm respectively. Also, we explored temperature effects on the structural properties of the La-BZN in the temperature range of 298 to 470 ◦K using the X-ray diffraction technique (XRD) for two samples with X= 0.10 and X= 0.20. The temperature dependent XRD analysis was employed to determine the temperature effects on the lattice constant, grain size, micro strain, dislocation density and degree of orientation. By increasing temperature from 298 to 390 ◦K, the strain, the dislocation density and lattice constant increased for both samples, while the grain size decreased in the same temperature range. In addition, the room temperature impedance spectrum was recorded in the frequency range from 10 to 1800 MHz. Physical parameters of capacitance, conductance, reflection coefficient, return loss and voltage standing wave ratio that are needed for using the La-BZN as an active vii resonator in telecommunication technology were investigated. These measurements provided information about the doping effects on the dielectric properties in this frequency range. The capacitance increased from 13.5 to 20.6 pF as the doping ratio increased from X= 0.10 to X= 0.22. The dielectric constant increased in the doping ratio range of X= 0.10 to X= 0.20 from 31 to 55.