Protonic Conduction in Phosphate Glasses

Protons in some alkaline earth metal-phosphate glasses are much more mobile than monovalent ions such as Na + and Ag + ions under a dc electrical field. The O-H bonding in those glasses that is weakened by the strong hydrogen bonding with neighboring nonbridging oxygen ions may cause the mobile protons. It has been generally accepted that protons of oxide glasses containing no molecular water carry no charge, or that if mobile, protons are much less mobile than alkali ions. Protonic conduction of crystalline solids has been reviewed 13 and some fast proton-conducting hydrated solids were prepared. 4 However, these hy-drated solids are chemically unstable, and they are not easily formed into thin film. Protonic conduction in glasses has some attention in the search for fast proton-conducting glasses for a solid electrolyte for H2-O2 fuel cells. The species of electrical charge carriers in alkali-free and transition metal-free oxide glasses has been an uncertain subject. Protons generally remain as O-