Broadband complex permittivity measurements of sorbitol during isothermal crystallization

Abstract Complex permittivity measurements of sorbitol were made during isothermal crystallization in a wide frequency range between 100 μHz and 500 MHz. It was found that the values of the relaxation strength for the α and the β processes decrease with time. It can be considered that this phenomenon simply corresponds to a decrease of the amorphous fraction due to crystallization. However, crystallization had a different effect on the α and the β processes because of the difference between the origins of these processes. It is remarkable that another relaxation process, we call α′ process, appears with longer relaxation time than that of the α process. The α process is considered to be the structural relaxation process of the amorphous fraction. The β process is thought as local process. It is suggested that the α′ process is caused by the regions of crystalline fraction from the behavior of the relaxation strength and time. It is difficult to assume that the origin of the β process of sorbitol is in islands with high mobility which represent the structural character remaining at higher temperatures.