(1810 - 1896)
Zoólogo alemán. Su labor científica fue enorme en el campo de las investigaciones zoológicas. Sus aportes se plasmaron en obras sobre mamíferos, aves, insectos, reptiles y moluscos.
Natural and Exact Sciences
2005 | "New approach in the characterization of ferroelectric systems starting from the study of ac answer and the behavior of electric conductivity"
Main executives entity:
Other entities:  Sao Carlos Federal University,  Brazil),  “José Antonio Echeverría” Higher Polytechnic Institute (ISPJAE)
Main author: Aimé Peláiz Barranco, Facultad de Física Universidad de La Habana
Coauthors: Francisco Calderón Piñar and Oscar Pérez Martínez from (IMRE), René López Noda (ICIMAF),. Osmany García Zaldívar (ISPJAE),. Irma González Carmenate (Faculty of Physics, University of Havana), José de los santos Guerra (Federal University of Sao Carlos, Brasil).

There were studied diverse ceramics (obtained by different preparation methods) and ferroelectric compound materials (polymer/ceramic), in relation to their ferroelectric properties, ac answer and the influence of electric conductivity on ferroelectric properties. It is presented a new approach in the analysis of ac answer's behavior on freezing temperature (Ft) and Curie temperature (Ct) for relaxer and normal ferroelectrics, respectively, as well as in the study of the influence of electric conductivity on its ferroelectric properties. It was developed and validated a relaxation model considering a distribution of relaxation times, starting from Debye model, which doesn't make considerations of the models previously established, constituting an important contribution to this subject. It was evaluated the behavior of the Universal Relaxation Law in relaxer and normal materials, and this topic was theoretically approached through the proposal of a model for the dependence of temperature of the exponents of this Law, unprecedented study in specialized literature. The validation of this model allowed establishing a new way of approaching the phase transitions in ferroelectric materials, starting from the Universal Relaxation Law. There were obtained PZN-PT-BT ceramics, in a non-studied range of compositions, with very good properties for practical applications, superior to those previously reported, and the PTCR effect was evaluated through ac answer. Lastly, there were obtained compound materials (polymer/ceramic) reported for the first time as a result of this research. It was evidenced a remarkable influence of electric conductivity on their ferroelectric properties and good properties for industrial applications, in particular to high frequencies. It was analyzed and modeled their ac answer, considering the contribution of each phase (ceramic and polymer).