BN fibers with cylindrical hollow structures were prepared from organic polymeric precursors through melt spinning, curing and pyrolysis processes. The microstructure, solid phase and morphologies of the synthesized hollow BN fibers were investigated by XRD, SEM and TEM, respectively. Moreover, the dielectric properties of BN hollow fibers were also measured. The results show that heating temperature and heating rate are the key factors affected the structure and dielectric properties of BN hollow fibers. Moreover, the BN hollow fibers synthesized in the optimized process conditions have good resistance towards oxidation up to 950 C in an oxidation atmosphere, and possess very low dielectric constant (epsilon') and loss tangent (tan delta) less than 3.30 and 0.00064 (7-18 GHz), respectively
