Durability and Ionic conductivity Flashcards
1
Q
Why is Na+ diffusivity in a silicate glass significantly greater than in NaCl?
A
~ in NaCl, Na+ diffusion needs the adjacent Na+ site be vacant and that Cl- ions move out of the way
~ an open glass network facilitates easy motion of Na+
~ higher conc of Na2O PUSHES NETWORK OPEN, facilitating Na+ migration
2
Q
How do alkali containing glasses become electrically conductive at high temp?
A
~ mobile Na+ ions, not e-
~ more Na2O dialates network, more Na+ mobility
3
Q
What trend is shown between alkali silicate glasses and high ionic conductivity?
A
~ Rb+<K+<Li+<Na+
~ ionic conductivity increases with decreasing cation size (smaller cations move with less displacement of surrounding ions)