Microspheres of tellurite glass formed by evaporation-condensation process under high magnetic field

Sodium tellurite glass was evaporated by irradiating a CO₂ laser beam under a high magnetic field with a large gradient. Glass microspheres were formed as a cloud of soot with the condensation of the vapor from the source glass. The flow of the glass soot due to thermal convection was observed when the glass source was evaporated under a zero field, but was suppressed by applying the high magnetic field with a large gradient, which reduces gravity for the glass by a magnetic force of -0.8g in the gravitational scale. The maximum size of the microspheres decreased to about half that of microspheres formed under a zero field. Sodium concentration in the microspheres was found to increase with magnetic field. A disturbance of the motion of evaporated species due to electromagnetic force was suggested as an origin of the suppression of recondensation to the surface of source glass melt under the high magnetic field, resulting in the increase in the sodium concentration of the microspheres and in the decrease in their size.