Study of ferroelectric properties of deuterated tris-sarcosine calcium chloride

By means of permittivity, spontaneous polarisation and polarisation reversal measurements the authors studied the influence of the substitution of deuterium atoms for hydrogen on the ferroelectric properties of tris-sarcosine calcium chloride (TSCC). Although most of the protons in the hydrogen bonds were substituted by deuterium (as checked by means of multi-pulse NMR techniques for solids and by infrared spectroscopic measurements) there is no change of the phase transition temperature. By combining density and NMR measurements it could also be shown that the volume of the unit cell did not alter for the various deuterated crystals. The absence of the deuteration effect on T_c and on the parameters of the Landau expansion of P_s suggests that a proton ordering in the hydrogen bond of the type N-H. . .Cl does not occur in practice. This behavior can be understood because the hydrogen bond is rather asymmetric so that the protons occupy predominantly equilibrium positions near the nitrogen atoms. For an interpretation of the results presented the theory of Chaudhury (1982) and co-workers may be applied.