Sintering temperature-dependence on radiopacity of Bi_(2-x) ZrxO_(3+x/2) powders prepared by sol-gel process

Bismuth oxide (Bi₂O₃) is an effective additive used to enhance radiography resolution for dental materials. However, there are potential concerns regarding its biocompatibility and connection to tissue discoloration. In the present study, we modified the radiopacity properties of Bi2O3 with zirconium oxide (ZrO₂) using a sol-gel process and investigated the composition, as well as the effects of heat treatment temperature using Thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The harvested Bi_2-xZr_xO_3+x/2 particles showed that the dominant phase transferred from α-Bi₂O₃ to β-Bi_7.38Zr_0.62O_12.31 after a heat treatment of over 750 °C for 2 h. As the x values of Bi_2-xZr_xO_3+x/2 increased from 0.2 to 1.0, more zirconium oxide precipitated onto the particle surface, thus enhancing the surface roughness of particles. For sol-gel Bi_1.8Zr_0.2O_3.1 powders (x = 0.2), the radiopacity values became 4.90 ± 0.23 and 5.83 ± 0.22 mmAl after a heat treatment of 500 °C and 750 °C, respectively.