New Superionic Conducting Glass-Ceramics in the System Na2O-Y2O3-Sm2O3-P2O5-SiO2: Crystallization and Ionic Conductivity

The glass-ceramics of the phosphorus induced Na5RSi4O12 (N5)-type (R = Y, Sm) Na+ superionic conductors in the systems Na2O-Sm2O3-P2O5-SiO2 and Na2O-Y2O3-Sm2O3-P2O5-SiO2 were prepared by crystallization of glasses with compositions Na3 + 3x - ySm1 - xPySi3 - yO9 and Na3 + 3x - yY(1 - x)/2Sm(1 - x)/2PySi3 - yO9, respectively. The optimum conditions for crystallization were discussed with reference to the conduction properties and the preparation of uncracked N5-type glass-ceramics. The crystallization of the N5 single-phase glass-ceramics was dependent strongly on the concentrations of both[R] and [P] (or x and y in the composition parameters) and the temperature for crystallization of glass specimens. Grain growth was promoted with the increasing heating temperature and heating time for crystallization. The Na+ ionic conductivities of the glass-ceramic Na4.1Sm0.5P0.4Si2.6O9 and Na4.1Y0.25Sm0.25P0.4Si2.6O9 were 4.78 × 10-2 and 2.79 × 10-2 S/cm at 300°C, respectively.