Fast-ion conducting glass and glass-ceramics for the pH sensor

• Main Author: Niyompan, Anuson
• Published: University of Warwick 2002
• Subjects: 530; QC Physics
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250950

Fast-ion conducting glasses of the compositions Na1+xM2-x/3SixP3-xOI2-2x3 (0≤ x ≤3), where M = Zr, Ti, were studied to determine their structural arrangement, physical properties and ionic conductivity. Glass samples were prepared using the conventional melt-quench method in the melting temperature range, 1550 °C to 1650 °C. Glass products were characterised by XRD, DTA, dilatometry and density measurement. Solid state MAS NMR experiments of three accessible nuclei, 23Na, 29Si and 31P were used to determine short-range order arrangement in the glasses. XRD confirms the amorphicity of glasses for the compositions of x in range 0-3. Glass transition temperatures, Tg. TEC, and molar volume are controlled by glass composition. The MAS NMR results suggest that glass structure could be visualised as the silicate network modified by Na+ and Zr4+ or Ti4+ and [PO4] tetrahedra link up with the remaining of these modifiers with no Si-O-P observed. The glass structures were also controlled by the compositions. Using parameters determined by DTA, the corresponding glass-ceramics were produced by heat treatment for 4 hr. The composition containing ZrO2 provided the fast-ion conducting crystalline phase at a small concentration. The major crystalline phase is Na2ZrSi2O7. Glass-ceramics containing TiO2 produce very small concentration of the crystallised phase. Ionic conductivity measurement was used to determine the electrical properties of glass and glass-ceramics. Glasses having high Na2O content showed the higher ionic conductivity compared to the others.