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Schiavo, L.; Aversa, L.; Verucchi, R.; Castaldo, R.; Gentile, G.; Carotenuto, G. Negative Temperature Coefficient Properties of Natural Clinoptilolite. Ceramics2024, 7, 452-465.
Schiavo, L.; Aversa, L.; Verucchi, R.; Castaldo, R.; Gentile, G.; Carotenuto, G. Negative Temperature Coefficient Properties of Natural Clinoptilolite. Ceramics 2024, 7, 452-465.
Schiavo, L.; Aversa, L.; Verucchi, R.; Castaldo, R.; Gentile, G.; Carotenuto, G. Negative Temperature Coefficient Properties of Natural Clinoptilolite. Ceramics2024, 7, 452-465.
Schiavo, L.; Aversa, L.; Verucchi, R.; Castaldo, R.; Gentile, G.; Carotenuto, G. Negative Temperature Coefficient Properties of Natural Clinoptilolite. Ceramics 2024, 7, 452-465.
Abstract
Negative temperature coefficient (NTC) materials are usually based on ceramic semiconductors and electrons are involved in their transport mechanism. A new type of NTC material, adequate for alternating current (AC) applications, is represented by zeolites. Indeed, zeolites are single-charge carrier ionic conductors with a temperature-dependent electrical conductivity. In particular, electrical transport in zeolites is due to the monovalent charge-balancing cations, like K+, capable of hopping between negatively charged sites in the aluminosilicate framework. Owing to the highly non-linear electrical behavior of the traditional electronic NTC materials, the possibility to have alternative types of materials, showing linearity in the electrical behavior, is very desirable. Among different zeolites, the natural clinoptilolite has been selected for investigating the NTC behavior since it is characterized by high zeolite content, convenient Si/Al atomic ratio, good mechanical strength, due to its compact microstructure, and low toxicity. Clinoptilolite has shown a rapid and quite reversible impedance change under heating, characterized by a linear dependence on temperature. X-ray diffraction (XRD) has been used to identify the natural zeolite, to establish all types of crystalline phases present in the mineral, and to investigate the thermal stability of these phases up to 150°C. X-ray photoelectron spectroscopy (XPS) analysis has been used for the chemical characterization of the natural clinoptilolite sample, providing important information on the cationic content and framework composition. In addition, since electrical transport takes place in the zeolite free-volume, a Brunauer–Emmett–Teller (BET) analysis of the mineral has been also performed.
Chemistry and Materials Science, Materials Science and Technology
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