Nasicon : Amorphous to crystalline compounds
Abstract According to previous studies, there are, at least, three fundamental problems for Nasicon compounds: 1. i) structural transitions are generally observed above the room temperature. The order of these transitions and associated thermal effects are depending on the fabrication process of NASICON compounds. 2. ii) Zr deficient compositions only exhibits slight changes of ionic conductivity in comparison with the stoichiometric one. 3. iii) There are two possible conduction pathways in the NASICON type structure jumping between Na(2) positions and jumping from Na(2) to Na(1) to Na(2). In this paper, we show that these problems are related to the great ability for NASICON compositions to give amorphous compounds by a tetrahedra orientational disorder mechanism.