| Abstract [eng] |
Impedance spectroscopy (IS) is a powerful technique used in applications such as electrochemistry, materials science, biology, medicine, and the semiconductor industry. This technique is based on the interaction of the electric charge of particles inside the sample with an applied electric field and essentially consists in measuring the magnitude of this interaction and its characteristic frequency or time scale. For this experiment, Na3VTi(PO4)2F3 glass as the initial sample is held in position with the electrode and the spectrometer was used to provide the electric field through the material and heated at a high temperature of (466.85 degrees Celcius) 740K to nanocrystalise and temperature maintained for 17 hours. During this time nanocrystallization was happening and we were measuring every half an hour impedance of the material, This process is called in-situ. The data was collected(33points) and every ½ an hour and a Bode and Nyquist plot were drawn. A small portion of the graph was considered which is far away as possible in the highest frequency side of the peak from the other side and draw an equivalent circuit. We take the most simple circuit which is R and CPE(not ideal capacitor). During the experimental implementation of impedance spectroscopy using equivalent circuit to analyse the results, it was quite impossible to determine the two processes because they were overlapping with each other. This brought about the DRT(Distribution relaxation time) which sorted the best possible way to clearly show that two processes exist since this method yields a better resolution. To recomfirm that actually two processes occured we performed gaussian fit of DRT using multipeak fitting and the results obtained clearly showed showed that two processes occured. Further more we fitted the impedance spectra in Zview using the center(Xc) obtained from the multipeak fitting(Figure 19 to 23) , and other parameters such as the distribution element(DE1 & DE2)(see appendix). This was to show that the other side of the graph(far away peaks) does not have any influence on the selected section. Values of the resistances were obtained for all times and The ratio of resistance( R2/R1) obtained from the Zview corresponded to the ratio of area ( A2/A1) under the Gaussian curve(Figure 29 to 31). |
