Synthesis and characterization of sol–gel derived ZrV2O7 fibers with negative thermal expansion property

Novel ZrV2O7 fibers with negative thermal expansion were prepared via combination of sol–gel process and thermal decomposition. The as-prepared fibers were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy and Raman spectroscopy. The results showed that the synthetic pH value had little influence on the crystal structure of products while showed significant effect on morphology. The fibers obtained at pH = 9 exhibited cylindrical morphology and its mean diameter was about 1 μm. The thermal expansion property of the as-prepared fibers was investigated by in situ XRD and thermal mechanical analyzer. All of the as-prepared fibers showed positive thermal expansion first and then negative thermal expansion, resulting from a phase transition from 3 × 3 × 3 superstructure to 1 × 1 × 1 cubic structure. The macro thermal expansion coefficients of ZrV2O7 ceramic rods increased with decreasing of fiber diameter. The mechanism of the phase transition was also discussed.