Effects of boron and phosphorus substitution on sodium-ion conduction properties of glass-ceramic Na₅FeSi₄O₁₂

Abstract

This study has focused on the effect of Si-substitution with alio-valent boron and phosphorus on sodium-ion (Na⁺) conduction properties of the newly developed glass-ceramic Na₅FeSi₄O₁₂. The glass-ceramics with the Na⁺ conducting single phase were obtained with the compositions Na_5+xFeB_xSi_4−xO₁₂ and Na_5−yFeP_ySi_4−yO₁₂, although the solubility limits were restricted as x < 0.4 and y < 0.3. The conductivity of the mother Na₅FeSi₄O₁₂ glass-ceramics was enhanced on both Na_5+xFeB_xSi_4−xO₁₂ and Na_5−yFeP_ySi_4−yO₁₂, and the maximum conductivities were achieved on the compositions Na_5.2FeB_0.2Si_3.8O₁₂ (x = 0.2) and Na_4.9FeP_0.1Si_3.9O₁₂ (y = 0.1), as high as 3.1 × 10⁻³ and 4.2 × 10⁻³ S cm⁻¹ at 300 °C, respectively.