Sol–gel synthesis of boron carbide from a polyvinyl borate precursor: effect of heat treatment temperature on phase formation

In this study, boron carbide (B₄C) was synthesized via the sol–gel method using polyvinyl alcohol (PVA) and boric acid (H₃BO₃) as precursor materials. After complete dissolution of PVA in water, boric acid was added to the solution, and the resulting mixture was filtered and subjected to pyrolysis at 600 °C. The pyrolyzed precursor was subsequently heat-treated at 1200 °C, 1300 °C, and 1400 °C under an argon atmosphere. The phase evolution and structural characteristics of the synthesized products were analyzed by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Thermal behavior was evaluated using thermogravimetric analysis (TGA), while the microstructural features of selected samples were examined by scanning electron microscopy (SEM). The XRD results indicated that boron carbide formation becomes more pronounced with increasing heat-treatment temperature. In particular, the sample treated at 1300 °C exhibited diffraction peaks corresponding to rhombohedral B₄C. TGA results showed relatively lower mass loss for this sample, suggesting improved thermal stability compared with the other samples. In contrast, the sample treated at 1400 °C exhibited changes in mass loss behavior that may be associated with the formation of additional phases during thermal analysis under a nitrogen atmosphere. Overall, the results suggest that heat treatment at 1300 °C provides favorable conditions for the formation of boron carbide within the investigated temperature range. The sol–gel route employed in this study offers a simple and potentially energy-efficient approach for the synthesis of boron carbide powders.