Structural Analysis of Doped BZN Pyrochlore Ceramics as a Function of Temperature Using Synchrotron Radiation رسالة ماجستير

Abstract

In this thesis, the structural properties of Bi1.5Zn0.92Nb1.5O6.92 pyrochlore ceramics doped with Cr, Ni and In were investigated using synchrotron radiation at SESAME. Changes in the interplaner spacing, lattice constant, micro-strain, crystallite size and dislocation density were studied. In the first part of this study, Cr, Ni and In doped BZN pyrochlore ceramics were studied at room temperature (RT). The lattice constant value obtained decreases with increasing the Ni content and increases with increasing the In content in the sample. The change in the lattice constant with changing the dopant content was interpreted as a result of the different ionic radius of the dopant atom. No new phases have been observed in these samples since they remained under the solubility limit. In the second part of this study, (0.10) Cr and (0.10) Ni doped BZN pyrochlore ceramics were studied in a temperature range of (RT-600) C˚, in a step of 25 C˚. It was observed that as temperature increases, the maximum peak shifts to lower angles increasing the lattice constant value gradually. In addition, increasing temperature have led to a greater shift in the peak at higher Bragg’s angles, which is attributed to the increase in the lattice constant with increasing temperature from 10.5485 A˚ to 10.5770 A˚ for the (0.10) Cr doped BZN, and from 10.5627A˚ to 10.5985 A˚ for the (0.10) Ni doped BZN. For the (0.10) Ni doped BZN pyrochlore, seven new XRPD peaks appeared at 25.57478˚, 35.17912˚, 43.40210˚, 52.60903˚, 66.61307˚, 76.94071˚ and 95.34664˚. The first three peaks were found to originate from Nb2O5, ZnO, and NiO phases respectively, while the rest of the seven new peaks are due to dislocations and stacking faults in the crystal structure of the sample. Finally, Thermal Expansion Coefficient (TEC) was calculated to be 4.9124 × 10 −6 ( 1 ℃ ) for the (0.10) Cr doped BZN pyrochlore ceramic and 6.1623 × 10 −6 ( 1 ℃ ) for the (0.10) Ni doped BZN pyrochlore ceramic.