Dielectric spectroscopy (DS) techniques play a major role in gaining insight into important peculiarities of dielectric responses of materials. The principles of DS of solids are discussed starting from simple concepts. The physical basis is presented, emphasizing the meaning of the magnitudes and phenomena involved, including the microscopic aspects of the chemical nature of solids. The applications, advantages, and limitations of DS are also discussed. Some examples are given that provide a practical overview of the main ideas as well as to show the usefulness of the technique.

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We have studied the transient response of some capacitor systems during the charging process to a step function voltage. The dielectric materials used were MOR type zeolites showing 80 % of crystalline phase, as determined by X-ray diffraction (XRD) Using the Fourier integral transform and the Kramers-Kronig relations we have obtained the real and imaginary part of the permittivity. In some of these spectra a negative capacity effect has been observed. This uncommon effect is interpreted through the "universal response law" for dielectrics relaxation in solids. Based on the strong low frequency dispersion mechanism a phenomenological approach is proposed to explain these results taking into account the physical properties and structure of the zeolites.