Crystal chemistry and ion conductivity of the Na1 + xTi2 − xAlx(PO4)3 (0 ≤ x ≤ 0.9) NASICON series (original) (raw)
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Solid State Ionics, 1997
The NASICON-type Na1.5Nb0.3Zr1.5(PO4)3 was prepared by solid state reaction of Nb2O5 and the precursor γ-NaHZr(PO4)2 at 700 °C. The EPR spectra showed a signal with a g factor of 1.984 assigned to Nb (IV) species in octahedral oxygen environments. The X-ray powder diffraction pattern obtained with monochromatic radiation was indexed on the basis of a rhombohedral cell, the hexagonal parameters being aH = 8.8061(2) and . The Na+ ion conduction was measured by the complex impedance method (frequency range: 0.1–105 Hz; temperature range: 20–500 °C) on four pellets previously sintered at 450, 750, 900 and 1000 °C. The conductivity data are discussed in relation to the sintering temperature. An activation energy of 0.60 eV for the movement of Na+ ions in the NASICON framework has been found.
Solid State Ionics, 2005
NASICON compounds have been prepared as polycrystalline powders. Rietveld analysis of X-ray and neutron diffraction patterns showed that M = Ge and Sn samples crystallize in the R3 space group (s.g.) and that M = Ti, Hf, Zr compositions crystallize in the R3c s.g. Data analyses indicated that aluminum contents into the main NASICON phases are always smaller than the nominal ones. 27 Al, 31 P and 23 Na magic angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies have been used to deduce aluminum contents and local atomic environments. In samples with high aluminum contents, M = Ge, Sn and Ti, electrical conductivity has been deduced from impedance spectroscopy data. The titanium sample incorporates the maximum aluminum content and displays the lowest activation energy, 0.52(1) eV, and the highest conductivity, r T (400 K)= 1.5(3) Â10 À 5 S cm À 1. The influence of structural parameters on conductivity values has been analyzed with the bond valence sum method. With this technique, the most probable conduction pathways in Na 1+x Al x Ti 2Àx (PO 4) 3 and Na 1+x In x Zr 2Àx (PO 4) 3 samples have also been deduced.
Powder Diffraction, 1997
It is known that solids with composition Na3Zr 2 Si2PO 12 heated at 1200 °C crystallize in the nasicon structure. This material shows a high ionic conductivity that represents an interesting improvement in the field of solid electrolytes. Our experimental results allow to establish for the first time that nasicon structures are stable along the compositional join Na 3 Zr 2-^/4Si2x Pi + x ®\2 w i m x extending from 0 to 1.667. These structures are characterized by a Zr underoccupation of octahedral sites and a constant number of Na + ions. This fact envisages a possible application of these materials in the field of ceramic sensors and ionic conductors.
High Lithium Ionic Conductivity in the Li1+xAlxGeyTi2-x-y(PO4)3 NASICON Series
Chemistry of Materials, 2003
Two Li 1+x Al x Ge y Ti 2-x-y (PO 4) 3 (0.2 e x e 0.8; y) 0.8, 1.0) solid solutions have been prepared as polycrystalline powders. These compounds crystallize in the NASICON-type structure, R3 hc space group, and the crystal structures have been characterized by the Rietveld method with laboratory X-ray powder diffraction data. The cell parameters evolution along the two series agrees with the substitution of larger Ti 4+ by smaller Ge 4+ and Al 3+ cations. The electrical properties have been characterized by an impedance study. Bulk conductivity values at room temperature are close to 10-3 S‚cm-1 with low activation energies (≈0.35 eV). The trajectories of the Li + cations have been simulated from the bond valence sum calculation. Structural keys, which justify the high ionic conductivity and the low activation energy, are discussed.
Solid State Communications, 2007
A novel inorganic solid electrolyte with a layered framework structure stable up to 1043 K, Na 14.5 [Al(PO 4 ) 2 F 2 ] 2.5 [Ti(PO 4 ) 2 F 2 ] 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 P3 with a = 10.448(2), b = 10.448(2), c = 6.589(3)Å, 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.
A Chemical Map of NaSiCON Electrode Materials for Sodium-ion Batteries
Na-ion batteries are promising devices for smart grids and electric vehicles due to cost effectiveness arising from the overall abundance of sodium (Na) and its even geographical distribution. Among other factors, the energy density of Na-ion batteries is limited by the positive electrode chemistry. NaSICON-based positive electrode materials are known for their wide range of electrochemical potentials,[1],[2],[3] high ionic conductivity, and most importantly their structural and thermal stabilities. Using first- principles calculations, we chart the chemical space of 3d transition metal-based NaSICON phosphates of formula NaxMM’(PO4)3 (with M and M’= Ti, V, Cr, Mn, Fe, Co and Ni), to analyze their thermodynamic stabilities and the intercalation voltages for Na+ ions. Specifically, we computed the Na insertion voltages and related properties of 28 distinct NaSICON compositions. We investigated the thermodynamic stability of Na-intercalation in previously unreported NaxMn2(PO4)3 and N...
The effect of magnesium doping on the structure and conductivity of NASICON as solid electrolyte
THE 4TH INTERNATIONAL CONFERENCE ON MATERIALS AND METALLURGICAL ENGINEERING AND TECHNOLOGY (ICOMMET) 2020, 2021
One of the problems that exist in the secondary sodium ion battery is the low working temperature of the electrolyte, which makes it easy to explode when exposed to free air. The type of solid electrolyte that can be used in high temperatures is NASICON (Natrium Super Ionic Conductor). In this study, magnesium was added to the NASICON structure to increase the ion conductivity of the solid electrolyte as a sodium ion-based battery electrolyte material. The synthesis method used is the solid-state reaction method by mixing sodium carbonate, silicon dioxide, zirconium oxide, ammonium dihydrogen phosphate, magnesium oxide and some anhydrous ethanol into a ball mill for 12 hours, dried at 80°C for 12 hours then calcined at temperature 1125 ° C for 12 hours with a heating rate of 2 ° C minute-1. Then the material is pressed at 15 MPa to produce pellets with a diameter of 10 mm and the sintering process is carried out at a temperature of 1175 ° C for 12 hours at a speed of 1 ° C minute-1. The doping used varies from 0 to 5 mol% of magnesium. XRD results showed that all variations showed a rhombohedral phase. The highest ionic conductivity value was 8.59 x 10-4 S.cm-1 with a magnesium doping variation of 2 mol%.
Ionic and Thermal Transport in Na-Ion-Conducting Ceramic Electrolytes
International Journal of Thermophysics
We have studied the ionic and thermal transport properties along with the thermodynamic key properties of a Na-ion-conducting phosphate ceramic. The system Na1+xAlxTi2−x(PO4)3 (NATP) with x = 0.3 was taken as a NASICON-structured model system which is a candidate material for solid electrolytes in post-Li energy storage. The commercially available powder (NEI Coorp., USA) was consolidated using cold isostatic pressing before sintering. In order to compare NATP with the “classical” NASICON system, Na1+xZr2(SiO4)x(PO4)3−x (NaZSiP) was synthesized with compositions of x = 1.7 and x = 2, respectively, and characterized with regard to their ionic and thermal transport behavior. While ionic conductivity of the NaZSiP compositions was about more than two orders of magnitude higher than in NATP, the thermal conductivity of the NASICON compound showed an opposite behavior. The room temperature value was about a factor two higher in NATP compared to NaZSiP. While the thermal conductivity decr...