Nominal vs. actual stoichiometries in Al-doped NASICONs: A study of the Na1.4Al0.4M1.6(PO4)3 (M=Ge, Sn, Ti, Hf, Zr) family

Na+ ion conductors of glass–ceramics in the system Na1+xAlxGe2−xP3O12(0.3≤x≤1.0)

“…The data was superior to that of Ref. [4], in which nominal Na 1.4 Al 0.4 Ge 1.6 P 3 O 12 compound as polycrystalline sintered specimen was synthesized. The improvement in the total ionic conductivities was likely due to a lower porosity and crack in the glass-ceramics.…”

“…The bands observed in the region 1300-900 cm −1 and 800-700 cm −1 were ascribed to the intramolecular stretching vibration of the PO 4 unit, whereas the bands between 650 and 400 cm −1 be assigned to the intramolecular O-P-O bending vibration [9,20]. Because of a distribution of shorter and longer corner-sharing phosphate PO 4 3− tetrahedral chains, the glass phase showed fewer absorption bands in the range of 750-500 cm −1 compared with the corresponding glass-ceramics [20]. The bands viewed in the region ∼1650 cm −1 in all samples were assigned to the bending vibration mode of free H 2 O molecule.…”

“…According to the equation: ω max RC = 1, the capacitance calculated therewith was of the order of 10 −10 to 10 −9 F, a typical value for the grain boundary contribution [21]. Since the spike was inclined to the real axis at about 60 • , it indicated a blocking response of the electrode [4].…”

“…NASICON-type materials with the general formula AM 2 (PO 4 ) 3 , where A is monovalent cation, M is tetravalent cation and P can be partially replaced by Si, have been widely researched during last few years because of their high ionic conductivity [1][2][3][4]. The materials are extensively used as solid state electrolytes in electrochemical devices such as SO 2 [5] and CO 2 sensors [6].…”

Characterization of Na1.3Al0.3Zr1.7(PO4)3 solid electrolyte ceramics by impedance spectroscopy

“…Despite such a high lithium ionic conductivity the sodium analogs have not been so extensively studied. There were several syntheses of Na 1+ x M x R 2 − x (PO 4 ) 3 compounds performed [15][16][17][18] and the properties of ionic migration of R = Ge, Ti, Sn, Hf, and Zr based compounds were in depth considered by Spanish groups [19][20][21]. They confirmed that the properties of the NASICON-type sodium conductors strongly depend on the ionic radii of the cations located in NASICON characteristic octahedral (M and R) sites, which takes a significant role in forming the pathways for migration.…”