Reactivity of NASICON with water and interpretation of the detection limit of a NASICON based Na(+) ion selective electrode.

The leaching of Na(+) ions from NASICON of composition Na(3)Zr(2)Si(2)PO(12) to the aqueous solution was evidenced. The origin of the Na(+) leaching was studied using Na(+) concentration and pH measurements as well as solution and X-ray analyses. The Na(+) released was mainly attributed to the dissolution of a second phase, predominantly amorphous. The rate of Na(+) release was found to be dependent on the inverse of the square of the particle size. It is proposed that it is controlled by diffusion within the particle. An effective diffusion coefficient was deduced to be of the order of 5x10(-10) cm(2) s(-1). The nature of the detection limit of the NASICON based Na(+) ion selective electrodes is discussed.