Investigation of the Effect of Additives an‎d Processing Parameters on the Microstructure, Mechanical an‎d Dielectric Properties of Si3N4- BAS Composite

11/15/2026 12:00:00 AM

The present study aimed to fabricate Si₃N₄/BaO–Al₂O₃–SiO₂ (BAS) glass–ceramic composite bodies containing titania an‎d zirconia additives with a celsian crystalline phase, high flexural strength, an‎d transparency to electromagnetic waves. Spark plasma sintering (SPS) was carried out under a nitrogen atmosphere at 1350, 1450, an‎d 1550 °C, an‎d the effects of heat treatment on crystalline phases, microstructure, flexural strength, an‎d dielectric behavior of the composites were investigated. The thermal behavior an‎d crystallization process of the glasses during sintering were also eva‎luated. Characterization was performed using Fourier-transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), dilatometry (DL), X-ray diffraction (XRD), scanning electron microscopy (SEM), three-point bending tests, an‎d a vector network analyzer (VNA). FTIR spectra an‎d dilatometry results revealed that titania acted as a glass modifier, while zirconia functioned as a network former. According to XRD patterns an‎d SEM micrographs, the celsian (BaAl₂Si₂O₈) phase crystallized in the glasses containing zirconia an‎d titania. The microstructure of composites sintered at 1350 °C consisted mainly of equiaxed α-Si₃N₄ grains an‎d a glassy phase, while at 1450 an‎d 1550 °C, polyhedral β-Si₃N₄ grains appeared. The relative density of the zirconia- an‎d titania-containing composites increased from 79.32% to 94.61% an‎d from 67.58% to 80.55%, respectively, with increasing sintering temperature. The corresponding flexural strengths increased from 120.23 MPa to 558.36 MPa an‎d from 61.88 MPa to 202.39 MPa. Composites sintered at 1550 °C were subsequently heat-treated at 1500 °C for 1 h under nitrogen, based on DTA results. XRD analysis confirmed that heat treatment enhanced β-Si₃N₄ formation an‎d celsian crystallization. Additionally, ZrN, ZrSiO₄, TiN, an‎d BaTiO₃ phases were detected in zirconia an‎d titania containing composites, respectively. Heat treatment improved the relative density an‎d flexural strength of the zirconia containing composite from 94.61% to 98.44% an‎d from 558.36 MPa to 652.71 MPa, respectively, an‎d of the titania-containing composite from 80.55% to 81.49% an‎d from 202.39 MPa to 281.84 MPa. The average dielectric loss tangent (tan δ) in the 8.2–12.4 GHz frequency range decreased from 0.014 to 0.009 for the zirconia-containing composite an‎d from 0.048 to 0.028 for the titania-containing composite after heat treatment.

كامپوزيت نيتريد سيليسيم/ شيشه , سلسيان , استحكام خمشي , خواص دي الكتريك

Si₃N₄/glass composite , celsian , flexural strength , dielectric properties

Farhood Heydari

Seyed Mohammad Mirkazemi