USE OF A NATURAL CLINOPTILOLITE MONOLITH AS THERMISTOR

Geomorphic clinoptilolite is a mechanically and thermally stable mineral substance, and such characteristics are rarely found in natural zeolites. In addition, clinoptilolite has very interesting electrical properties due to the presence of extra-framework cations in the crystal structure. Indeed, owing to the electrical transport by hopping mechanism that alkali cations may give, this ceramic material behaves like an electrical insulator at room temperature, while it changes to an electrical conductor with the increasing of temperature. Such unusual electrical property of clinoptilolite can be advantageously exploited for a number of functional applications in the industrial field like, for example, thermal sensors, electrical/thermal switches, thermistors, etc. Here, the capability of a simple natural clinoptilolite monolith to switch from electrical insulator to conductor under fast and slow thermal changes has been investigated by a.c. electrical transport measurement (i.e., time-resolved high-frequency micro-current measurements).