Electrolyte NASICON

Zhu, Q., Qiu. F., Quan, Y., Sun, Y.. Liu. S. and Zou, Z. (2005) Solid-electrolyte NASICON thick film CO2 sensor prepared on small-volume ceramic tube substrate. Mater. Chem. Phys., 91 (2-3), 338-42. 

Nasicon solid electrolyte electrochemical promotion with, 440 sodium ion conductor, 440 NEMCA, see electrochemical promotion NEMCA coefficient, 152,319... 

A similar device with Nasicon solid electrolyte Na3Sc(P04)3 is used when analyzing the concentration of nitrogen oxides in air. The electrochemical system in this sensor can be formnlated as... 

The use of framework structures to minimize AH for alkali-ion electrolytes has been demonstrated to provide a means of opening up the bottlenecks to cation motion in a number of oxides (Goodenough, Hong and Kafalas, 1976). Framework structures may provide one-dimensional tunnels as in hollandite, two-dimensional transport in planes as in the )S-aluminas, or three-dimensional transport as in NASICON and LISICON. Since one-dimensional tunnels are readily blocked, the two-and three-dimensional conductors are the more interesting. 

A novel LiNiV04 positive material, having a voltage of approximately 4.8 with respect to Li, has been characterized and proposed for high voltage lithium ion batteries. However, its practical use may be limited by the lack of electrolytes capable of withstanding its high oxidation potential. Other recent developments include NASICON-related framework structures, such as a Fe2(S04)3-based compound. 

This is achieved in the electrochemical C02 sensor to be described now. The gas sensitive electrode in the emf sensors for C02 detection is based on an alkaline or alkaline earth carbonate.41"43 If Na2C03 is to be used, Na- (5" -alumina or Nasicon (Part I2) are suitable electrolytes. A thermodynamically well-defined sensor is obtained by using a mixture of a binary and a ternary oxide such as42 Na2C03, C02 Na+ -conductorj Na2M03, M02... 

Instead of the system silica/silicate also other systems such as titania/titanate, zirconia/zirconate can be used as a reference system [xiv]. The response time of freshly fabricated thick-film sensors based on thin-film /3-alumina is very short (about 15 ms at 650 °C). After several weeks of operating this time increases 10 times (150 ms) [xv]. Solid electrolyte C02 sensors using Ni/carbonate composite as measuring electrode are suited for measuring of C02 in equilibrated water gases [xiv]. Using semiconducting oxides and carbonates like ITO (indium tin oxide) Nasicon-based C02 sensors are able to measure at room temperature [xvi]. 

Crystalline solid electrolytes such as a-Agl, ji-alumina, NASICON, and LISICON, LLN, oxide ion conductors such as yttria-stabilized zirconia, etc ... 

Upon discharge sodium ions diffuse through the sodium-conducting /J- or -alumina or NASICON -> solid electrolyte. On the outer surface of the solid electrolyte they react with molten sulfur and/or low valency sulfide anions forming negatively charged polysulfide anions. The rather low electric conductivity of molten sulfur is improved by addition of tetracyanoethylene... 

Appreciable ionic conductivity is found in open framework or layered materials containing mobile cations (see Ionic Conductors). Several phosphates have been found to be good ionic conductors and are described above NASICON (Section 5.2.1), a-zirconium phosphates (Section 5.3.1), HUP (Section 5.3.3), and phosphate glasses (Section 5.4). Current interest in lithium ion-conducting electrolytes for battery apphcations has led to many lithium-containing phosphate glasses and crystalline solids such as NASICON type titanium phosphate being studied. ... 

Forsyth, M., Wong, S., Nairn, K., Best, A., Newman, P., and MacFarlane, D., NMR studies of modified NASICON-like, lithium conducting solid electrolytes. Solid State Ionics, 124, 213, 1999. 

Sodium ion conduction in /S"-alumina is anisotropic and ceramic electrolytes produced from this material not only can be sensitive to exposure to moisture but also are somewhat difficult to densify (e.g., because of problems related to NaaO evaporation, conversion to single-phase / -alumina, and control of exaggerated grain growth). For these reasons. Serious attempts have been made to find alternative materials that have Na" ion conductivities comparable to or higher than / "-alumina but are easier and/or potentially more economical to fabricate. Here we review attempts to develop alternatives. They fall into two classes of materials the crystalline NASICON family of compounds and conducting glasses. 

Preparation of Solid State Electrolytes 17.3.7.2. Alternative Sodium Ion Conductors 17.3.7.2.1. NASICON. 

The data presented in Table 1 permit several conclusion to be drawn on the potential use of these materials as electrolytes in electrochemical devices with practical values for the area-specific resistance. Only the j0"-alumina and NASICON electrolytes possess sufficient conductivities for use as membranes with thicknesses of 1 mm or greater. The sodium ion conductivities of polycrystalline NASICON and /l"-alumina are comparable. The glassy electrolytes must be used in the form of thin films ( < 50 pm and possibly under 10-15 pm) or as capillary tubes with very thin walls (10-50 pm). 

When the discovery of NASICON was first announced, its preparation was claimed to be free of the difficulties attributed to the processing of 8"-alumina electrolytes " . Since that time, considerable effort has been devoted to powder synthesis, forming, and... 

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