All-trans-1,6-diphenyl-1,3,5-hexatriene (ttt-DPH) exists in solution as a mixture of s-trans,s-trans and s-cis,s-trans conformers. The latter is higher in energy, and its contribution increases with increasing temperature. ttt-DPH UV absorption spectra broaden with increasing temperature and undergo blue shifts with decreasing polarizability. We describe here the resolution of two spectrothermal matrices of ttt-DPH UV absorption spectra into two conformer-specific components. The first matrix consists of DPH spectra measured in n-dodecane in the 283 to 374 K T range and the second of ttt-DPH absorption spectra measured in the even numbered n-alkanes (n-C(8)-n-C(16)) at temperatures selected to achieve isopolarizability (284-372 K). Principal component analysis (PCA) treatments showed that reasonable two-component systems are attained by compensation for T-induced broadening and shifting in the pure conformer spectra. The self-modeling (SM) method used to resolve the n-C(12) matrix is successfully tested on a simulated matrix closely mimicking ttt-DPH experimental spectra in n-C(12). Compensation for nonlinear effects yields robust two-component matrices from the experimental spectra. Their resolution into pure component spectra is based on the application of the Lawton and Sylvestre (LS) non-negativity criterion at the spectral onset to define the spectrum of the low energy s-trans-conformer and the optimum linearity van't Hoff (vH) plot criterion to find the spectrum of the higher-energy s-cis-conformer. Resolved spectra are somewhat sensitive to the choice of the spectral region in which the LS criterion is applied. The surprising result is that both resolutions lead to the conclusion that the molar fraction of the s-cis-conformer equals, or even exceeds, the molar fraction of the s-trans-conformer as the highest T's employed in our study are approached.

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Sr 0.2 Na 0.4 Nd 0.4 Bi 4 Ti 4 O 15 is prepared by Sol-Gel route using the modified polymeric precursor method based on the Pechini process and its electrical properties are investigated by Complex Impedance Spectroscopy (CIS). Results are presented in two ways, complex plane plots (real versus imaginary) and spectroscopic plots (real and imaginary against frequency). CIS has provided convincing evidence for the existence of both grain (bulk) and grain-boundary effects that were separated in the frequency domain of the impedance spectrum. Experimental data are fitted to two parallel RC equivalent circuits in series. The values of resistance and capacitance of bulk and grain boundary contributions are also calculated. Relaxation times are calculated for both grains and grainboundaries. Conduction and charge carrier behaviors are studied from frequency and temperature dependence of ac conductivity. The ac conductivity follows a two-power law behavior at different temperatures with frequency exponents s 1 and s 2 .

The processing conditions, microstructure, and dielectric properties of strontium bismuth titanate (SBT) were systematically studied. The specimen was synthesised by a mechano-chemical processing route using a planetary ball mill. It is important that the action is vigorous enough to break up loose aggregates and a fine particle size is obtained. The specimen was calcined at 800 o C for 4 h. The calcined samples were subjected to cold isostatic pressing (CIP) process and finally sintered at 1200 o C for 2 h. A relative density 90 per cent of the theoretical density was obtained. Pellets having a diameter of 1cm and thickness of 1 mm were prepared from the sintered compacts for electrical measurements. X-ray diffraction showed that a single phase with the layered perovskite structure of SBT was formed. Morphological studies were carried out by SEM analysis. Frequency dependence of impedance can provide additional insight into mechanisms controlling the electrical response. Resonance studies were made on poled sample in the frequency range 100 kHz -20 MHz using an impedance analyser (HP-4294A) interfaced to a computer at room temperature. Dielectric measurements in the frequency range 100 Hz-1 MHz were made using an impedance analyser (HP-4192A) interfaced to a computer and the measurements were carried out from room temperature to 550 o C. The ferroelectric hysteresis loop was measured using a standard ferroelectric analyser based on Sawyer-tower circuit. Elastic compliance (s 33 , s 11 ) coupling factor (k 33 , k 31 )were also obtained. These materials can be utilised in practical applications as substitutes for lead titanate and lead zirconate titanate (PZT)-based ceramics, where high temperature applications are foreseen.Keywords: Strontium bismuth titanate, synthesis, characterisation, resonance, dielectric measurement, SBT, perovskite, mechano-chemical processing

Sr 0.6 Na 0.2 Nd 0.2 Bi 4 Ti 4 O 15 ceramic is prepared by mixed oxide method. Lattice parameters for this ceramic are calculated from the X-ray diffraction data. Dielectric studies as a function of temperature and frequency are done. To understand the process of conduction involved in the material prepared, frequency and temperature dependency of AC conductivity studies are carried out. The two-term power relation is used to characterize the frequency dependence of AC conductivity. The parameters s1, s2 (low and high frequency slopes) are calculated from the AC conductivity plots at different temperatures to get more information about the conduction mechanism. Conduction is explained based on hopping mechanism occuring via polarons.