Far-Infrared and Millimeter Wave Spectroscopy of Halides-Doped Silver Phosphate Glasses

Abstract

Structural change by halides-doping into silver phosphate glass was studied by terahertz spectroscopy. The spectral change of far-infrared region suggests following model of structural change; the doped metal ion substitutes silver ions which were connected with non-bonding oxygen in proportion to its valence. The released silver ions contribute to ionic conduction. The halogen ions expand conduction channel for the silver ion between glass network chains of PO 4 tetrahedra. This expansion is small in the case of bromide-doping therefore the conduction channel is narrow than in the case of iodide-doping. New millimeter wave absorption bands were observed. Molecular dynamics simulation calculation was also executed.KEYWORDS: far-infrared, millimeter wave, conducting, silver phosphate, glasses IntroductionThe enhancement of ionic conductivity by metal iodide doping into silver phosphate glass has been reported with BiI 3 , CdI 2 and other metal iodides.1,2) The increase of ionic conductivity is proportional to exponent of the dopant concentration and valence number of the metal ion. Meanwhile, silver bromide doped silver phosphate glass has less ionic conductivity than the iodide-doped one. These facts suggest the following mechanism of the enhancement of ionic conductivity; the doped metal ion substitutes silver ions which were connected with non-bonding oxygen according to their valence and the released silver ions contribute to ionic conduction. The halogen ions expand conduction channel for the silver ion between glass network chains of PO 4 tetrahedra. This expansion is small in the case of bromide-doping therefore the conduction channel is narrow than in the case of iodide-doping. This paper reports results of far-infrared and millimeter wave spectra of metal bromides and iodides doped silver phosphate glasses to investigate ionic motion in the above mentioned model of glasses.