No abstract

No abstract

The sodium aluminum diphosphate compound has been synthesized by the classic ceramic method and characterized by X-ray diffraction technique, IR, 31 P NMR, 23 Na NMR and impedance spectroscopy. It crystallizes in monoclinic space group P2 1/c . The MAS-NMR spectra showed two and one isotropic resonances relatives to 31 P and 23 Na, respectively, revealing the existence of two phosphorus and one sodium environments in the structure. The electrical properties of this compound have been measured in the temperature range from 523 to 673 K and the frequency range from 209 Hz to 5 MHz. The Nyquist plots are fitted to an equivalent circuit modeled by a combination series of two parallel (R//C) and (R//CPE). Impedance measurements show NaAlP 2 O 7 an ionic conductor being the conductivity 1.16 9 10 -5 Xcm -1 at 613 K and E a is 0.95 eV. The conductivity provide nearly the same activation energies for electrical relaxation of mobile ions revealing that transport properties in this material appear to be due to an ionic hopping mechanism dominated by the motion of the Na ? ions along [101] tunnels direction presented in the structure of the investigated material. The peak positions x p of M 00 spectra shift toward higher frequencies with increase in temperature.

No abstract

No abstract

No abstract

No abstract

The (C 7 H 12 N 2 ) 2 [SnCl 6 ]Cl 2 ·1.5H 2 O complex is a new member of the family of hybrid organic-inorganic perovskite compounds. It exhibits two orderdisorder phase transitions with changes in the conformation of aromatic cations at the two transition temperatures 360 and 412 K. Differential scanning calorimetry, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FT-IR) spectroscopy were used to investigate these phase transitions. These transition mechanisms were investigated in terms of the spin-lattice relaxation times T1 for 1 H static NMR and the chemical shifts for 13 C CP-MAS. The temperature dependence of T1( 1 H) and 13 C chemical shifts are changed near T C1 and T C2 . Furthermore, the splitting for 13 C NMR signals in Phases (II) and (III) indicated a ferroelastic characteristic of the compound. In addition, FT-IR results indicate that the ordered conformational structure of aromatic cations undergoes a remarkable disorder with increasing temperature. The NMR and FT-IR studies suggest that the phase transition mechanisms are related to the reorientational motion of [C 7 H 12 N 2 ] 2+ cations as a whole. Phase transition was examined in light of the interesting optical properties of this material.