RARE-EARTH CONTRIBUTION IN SOLID-STATE ELECTROLYTES, ESPECIALLY IN THE CHEMICAL SENSOR FIELD

In solid state electrolytes, rare earths are commonly used, and a numb er of their properties are exploited in these applications. Firstly, t he rare earth can be utilized as a dopant to produce the mobile ion va cancies in an electrolyte and to enhance the ionic conducting characte ristics. Secondly, they can be used as the principal constituent of th e electrolytes. In both these case, the characteristics that the rare earths hold a stable trivalent state even though the main ionic mobili ty is via mono- or trivalent ions. Thirdly, the rare earth trivalent i on alone can migrate in some solids. This unexpected feature has been recently clarified by selecting the appropriate structure for the triv alent ion conduction in order to reduce the electrostatic interaction between the mobile ions and the framework of the solid. In solid elect rolytes, only one ionic species can migrate. This feature is very adva ntageous for chemical sensor applications, especially from the viewpoi nt of selective and quantitative detection of specific gas species, Th e rare earth contribution to solid state electrolytes has been rapidly increasing, and has been expanding further the realms of application not only in the industrial field but also in the whole science field. Here, the rare earths contribution to the solid state electrolyte fiel d is briefly reviewed.