Structure and electrical conductivity of a novel inorganic solid electrolyte: Na14.5[Al(PO4)2F2]2.5[Ti(PO4)2F2]0.5 (NATP)

A novel inorganic solid electrolyte with a layered framework structure stable up to 1043 K, Na14.5[Al(PO4)2F2]2.5[Ti(PO4)2F2]0.5 (NATP), has been hydrothermally prepared and characterized by single-crystal and powder X-ray diffraction techniques, X-ray fluorescence (XRF) analysis, IR spectroscopic measurement, thermogravimetric and differential thermal analysis (TGA and DTA). NATP crystallizes in the acentric hexagonal space group P 3 with a = 10.448 ( 2 ) , b = 10.448 ( 2 ) , c = 6.589 ( 3 ) إ , Z = 1 , containing a large number of Na+ cations in the interlamellar space and the cavities of its framework. There are six different crystallographic Na+ cationic sites, in which 8% Na(5) and 12% Na(6) sites are vacant. Electrical conductivity measurements show that Na+ cations exhibit a high mobility with two domains for the electrical conductivity versus temperature.