Ionic Conductivity of the NASICON-Related Thiophosphate Na1+xTi2-xGax(PS4)3

Inspired by the recent interest in fast ionic conducting solids for electrolytes, the ionic conductivity of a novel ionic conductor Na1+xTi2-xGax(PS4)(3) has been investigated. Using X-ray diffraction and impedance spectroscopy the sodium ionic conductivity in this compound was demonstrated, in which bond valence sum analysis suggests a tunnel diffusion for Na+. Substitution with Ga3+ leads to an increasing Na+ content, an expansion of the lattice and an increasing conductivity with increasing x in Na1+xTi2-xGax(PS4)(3). Given the relation to the NASICON family, upon replacement of the phosphate by a thiophosphate group, a rich structural chemistry can be expected in this class of materials. This work demonstrates the potential for making NaTi2(PS4)(3) an ideal system to study structure-property relationships in ionic conductors.