Effect of Mechanical Vibration on the Crystallization Behavior of ZBLAN Fluoride Glass Under Controlled Thermal...

ZBLAN (ZrF₄-BaF₂-LaF₃-AlF₃-NaF) fluoride glass is a promising infrared optical fiber material because of its wide transmission window and low theoretical attenuation; however, unwanted crystallization during thermal processing can introduce scattering centers and degrade optical performance. Previous studies have mainly focused on temperature effects and microgravity-based crystallization suppression, while the role of mechanical vibration remains insufficiently understood. This study addresses this gap by investigating how controlled mechanical vibration influences crystallization onset, morphology, and structural evolution in ZBLAN glass during short-duration thermal treatment. ZBLAN samples were treated at selected temperatures with and without vibration using a custom heating-vibration apparatus and characterized by optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and X-ray diffraction (XRD). Temperature-only treatment produced a gradual transition from transparent amorphous glass to crystallized structures with increasing temperature. Vibration-assisted treatment altered crystallization behavior, producing distinct needle-like, bow-tie, and feather-like morphologies depending on temperature and vibration intensity. AFM confirmed a significant increase in surface roughness, while XRD verified structural evolution from amorphous to highly crystallized states. At higher vibration levels, irregular crystallization suggested that excessive sample movement may reduce thermal contact and change the effective heating condition. These findings demonstrate that mechanical vibration is a critical and controllable processing variable in ZBLAN fabrication and should be carefully managed to suppress unwanted crystallization in both terrestrial and space-based fiber manufacturing.