Microanalysis of a fluoride glass preform

Abstract

During development of a method of fabricating fluoride glass preforms for drawing into optical fibres, in which core and cladding glasses are in intimate contact, back-scattered electron imaging revealed two distinct layers in the interface between the two glasses. The compositions of the two layers were found to be different from each other and different from either core or cladding glass. The compositions of these layers and of adjacent glasses were analysed using electron probe microanalysis and wavelength-dispersive X-ray spectroscopy (EPMA/WDS). Back-scattered electron imaging (BEI) was used to make a reasonable qualitative estimate of lithium distribution in the glasses, which could not be measured by EPMA/WDS. As part of a study of the nature of interfaces in glasses, possible mechanisms of formation for such interfacial layers and the effects of the different compositions on properties such as viscosity, refractive index, glass stability and fibre performance are discussed.