Study of the Relaxational Properties of Crystals, Glasses and Glassy Crystals.

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Vibrational and configurational degrees of freedom of a substance in a condensed phase have widely different time scales involved in their relaxational properties. The vibrational relaxation takes place in a short time that can be studied by eg. line width measurement of the vibrational spectra. The configurational relaxation is usually a much slower process and studied by dielectric, mechanical and other relaxational spectroscopies. This degree of freedom is excited significantly in configurationally disordered substances. In this research project we are concerned with the relaxational properties of disordered substances in the thermodynamic non-equilibrium state. A substance in thermodynamic non-equilibrium is called a glassy substance. The glassy state thus envisaged can occur not only in amorphous substances but also in disordered crystals. Relaxation in glassy substances has an unusual property that the temperature cannot be defined even locally.We constructed an apparatus for sim … More ultaneous measurement of the relaxation of the enthalpy and the dielectric polarization. The enthalpy relaxation is measured as a change of the temperature (ie., the vibrational temperature) of the sample kept in an adiabatic condition. Spontaneous rise and fall of the temperature indicate the decrease and increase, respectively, of the configurational enthalpy. The polarization relaxation is measured as the depolarization current.Rubidium cyanide, potassium cyanide-potassium bromide solid solutions, ice doped with lithium hydroxide and ammonium dihydrogen phosphate-rubidium dihydrogen phosphate solid solutions were studied calorimetrically. The first three substances underwent relaxational transitions at 30 K, 27 K and 62 K, respectively. Analysis of the relaxation times and the increment of the heat capacities showed that they are glassy crystals. The configurational ordering in the last substance took place without causing anomalies in the thermal properties. The polarization relaxation measurement is now under way. Less