Phase transition, nonlinear optical parameters and electrical properties in 4-benzylpiperidinium tetraoxoselenate monohydrate

The thermal properties of the organic-inorganic hybrid material (C12H10N)(2)SeO4H2O have been investigated using X-ray diffraction, Raman spectroscopy, impedance and modulus spectroscopy technique. Single X-ray diffraction recorded at three different temperatures: T-1 = 81 K, T-2 = 298 K and T-3 = 328 K reveals that the title compound crystallizes in the same space group (P21=c) for the different temperatures and the lattice parameters don't exhibit a remarkable variation. The nonlinear optical parameters exhibit a remarkable variation. This result indicates clearly that this material does not present a structural phase transition and confirm our previous interpretation of order disorder phase transition detected by DSC measurement at 300 K. Raman spectroscopy at various temperatures confirms the presence of the phase transition at 300 K and showed that both anionic and cationic motions contribute to the transition mechanisms. The character order disorder phase transition is undoubtedly related to the change in dynamical state of (SeO4)(2-) anion coupled with conformational change of [C6H5CH2C5H9NH2](+) cation above 300 K. The close values of activation energies obtained from the analysis of hopping frequency, electric modulus and dc conductivity indicate that the transport in the title compound can be described through a simple hopping mechanism, dominated probably by the orientation of selenate anions. Hence, in all temperatures the large gamma value shows that the studied compound is in interest material for NLO applications.