Dielectric Properties of K1−x\text{}_{1-x}(NH4\text{}_{4})x\text{}_{x}H2\text{}_{2}PO4\text{}_{4} (x= 0.095) Crystal

Temperature dependences of the dielectric permittivity were studied for the ferroelectric K$\text{}_{1-x}$(NH$\text{}_{4}$)$\text{}_{x}$H$\text{}_{2}$PO$\text{}_{4}$ mixed crystal. The experiments revealed presence of the beginning of the dipolar glass - embryos in the concentration of ammonium x=0.095. Observations of the dielectric relaxations show much bigger effect domain mechanism than the one related to the growth of clusters of the dipolar glass

Structural and dynamical aspects of the phase transition in the new thiourea thiazolium bromide inclusion compound.

International audienceA new thiourea thiazolium bromide inclusion compound is presented here. Detailed investigations of its phase transition were performed by differential scanning calorimetry, x-ray diffraction, and dielectric and nuclear magnetic resonance spectroscopy methods, completed by calculation of the steric hindrances for molecular reorientations and simulations of the second moment of the nuclear magnetic resonance line by the Monte Carlo method. A second order ferrielectric structural phase transition has been detected at 190.5 K as thiazolium cations collectively reorient inside channels. The dynamics is discussed in terms of inequivalent energy barriers associated with cation rotation as the symmetry breaking occurs. Oscillations of thiourea molecules and NH(2) groups have been also observed