Ionic Conductivities and Glass Transition Temperatures of Na2 O  ‐ ZrO2 ‐ Al2 O 3 ‐ SiO2 Glasses

Abstract

The present work extends the study of the thermal and electrical properties of glasses in the Na20-A120~-SiO2 and Na20-ZrO2-SiO~ systems and provides data on new glasses in the Na20-A1203-ZrO2-SiO2 system. The data show that these sodium-ion-conducting glasses have desirable characteristics for use in sodium/sulfur cells, i.e., a p of 100-200 ~-cm at 300~ and a Tg of 500~176 Sodium-ion-conducting ceramics and glasses have a broad range of potential applications as electrolytes in sodium/sulfur cells, sodium heat engines, sodium electrowinning devices, and sodium-ion-sensing analytical devices. Typical of the ceramic electrolytes are ~ and ~" alumina (1, 2) and NASICON (3), which have resistivities of 5-10 fl-cm at 300~ . The glass with the longest history of development as a sodium/sulfur cell electrolyte is a sodium borate glass (4-6) with a resistivity of about 2 • 104 f~-cm at 300~ Sodium/sulfur cells using the ceramic electrolytes have a single electrolyte tube a few centimeters in diameter; cells using the borate glass, because of its high resistivity, require thousands of hollow glass fibers, each about 10 -~ cm in diameter. In spite of its greater complexi}y, the cell with the glass electrolyte has continued to be of interest because of its potential for very low cost and very high power. Recently, silicate glasses of lower resistivity have been proposed for this application. These include: (i) a soda-alumina-silica glass (7) (900 12-cm at 300~(ii) a sodazirconia-magnesia-silica glass (8) (700 12-cm at 300~ and (iii) a soda-zirconia-silica glass (9) (600 f~-cm at 300~These lower resistivity glasses would allow a reduction in the number of tubes per cell from thousands to hundreds, which would simplify cell construction.In this study, we investigated twenty-three glasses in the Na~O-ZrO~-Al~O3-SiO~ system with the objectives being: (i) determination of properties as a function of composition so that the glass could be tailored to various applications as desired, and (ii) development of a glass electrolyte for sodium/sulfur cells with the lowest possible resistivity, consistent with the parallel requirement for high chemical stability in the cell environment. Earlier thermodynamic calculations (9) of the stability of sodium silicates in sodium and sulfur, as well as research by Elyard and Rawson *Electrochemical Society Active Member.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 35.8.11.2 Downloaded on 2015-06-11 to IP Vol. 133, No. 10 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 35.8.11.2 Downloaded on 2015-06-11 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 35.8.11.2 Downloaded on 2015-06-11 to IP

Chemical Stability of Na2 O ‐ ZrO2 ‐ Al2 O 3 ‐ SiO2 Glasses in Sodium, Sodium Polysulfides, and Sulfur

“…The compositions, including impurities, were determined by inductively coupled plasma/atomic absorption spectroscopy (ICP-AES). The major components of the glasses have been reported previously (15).…”

“…Twenty-two glass disks with soda-alumina-zirconiasilica compositions spanning the region of interest (25-50 m/o soda) were available from another study (15). The compositions, including impurities, were determined by inductively coupled plasma/atomic absorption spectroscopy (ICP-AES).…”

“…The weight-change data (mg/cm'-') and the reported glass compositions (15) were treated by cluster analysis (17) and then by multiple linear regression analysis (18) using a quadratic polynomial y = a~ + a,x, + azx~ + a:~x:, + a~,x, ~ + a,zx~x., + a22x., "2 + a~:~x~x:~ + a2:~x2x:~ + a:~:~32:~ ~ [17] where y is the observed weight change and the xj is the mole fraction for three independent components.…”

“…In our research, we have been concentrating on sodium-silicate based glasses with alumina and zirconia as modifiers of the resistivity, glass transition temperature (T~), and chemical stability. Glasses in this quaternary system have been developed with resistivities at 300~ of 130 to 3700 tbcm and T,'s of 400 ~ to 800~ (15). Chemical stability tests of these glasses in Na, S, Na2S4, and Na~S:~ at 400~ for 1000h were conducted to determine the optimum glass composition.…”

Ceramic/Glass Electrolytes for Sodium‐Ion‐Conducting Applications

“…In the literature, many different varieties of sodium-ionconducting glass have been reported, with resistivities ranging from 2 • 104 (2)(3)(4) to 165 ~-cm at 300~ (8). Glasses, despite these comparatively high resistivity values, are still the subject of much interest because they can lead to a sodium-based electrochemical cell with very high power and low potential cost.…”