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<p>Crystallization of the prepared transparent 2MgO-2Al₂O₃-3.33B₂O₃ glass system into a well glass-ceramic with optimized crystalline phases that simultaneously improve dielectric properties and lower thermal expansion (CTE) for enhanced functional performance. Despite its chemical equivalence to cordierite stoichiometry (2MgO-2Al₂O₃-5SiO₂), the investigated composition completely substitutes SiO₂ with B₂O₃. The nucleation efficiency of individual (TiO₂, ZrO₂) and combined TiO₂-ZrO₂ additives was rigorously evaluated. The glass-ceramics developed in this work exhibit tailored physicochemical properties (density, hardness, CTE, dielectric properties). Differential thermal analysis (DTA) identified a high crystallization (773–794&#xa0;°C) for TiO₂-ZrO₂-doped formulations. Phase evolution studies confirmed the crystallization of kotoite (Mg<sub>3</sub>B<sub>2</sub>O<sub>6</sub>), sinhalite (MgAlBO<sub>4</sub>), aluminum borate (Al₄B₂O₉), baddeleyite (ZrO₂), and aluminum titanate (Al₂Ti₇O₁₅) at 800–900&#xa0;°C. The SEM analysis of 900&#xa0;°C-treated samples revealed a microstructure of submicron rod-like crystallites dispersed in a residual glass phase. Thermo-mechanical characterization yielded CTEs of 12.42–27.55 × 10⁻⁷ °C⁻¹ (25–300&#xa0;°C) and 22.45–39.19 × 10⁻⁷ °C⁻¹ (25–400&#xa0;°C). The glass-ceramics (density: 2.54–2.65&#xa0;g/cm³; hardness: 5.42–5.85 GPa) exhibited superior dielectric properties (high dielectric constant, low dielectric loss) relative to parent glasses (2.61–2.73&#xa0;g/cm³; 5.11–5.89 GPa), attributable to TiO₂/ZrO₂-derived crystalline phases (Al₂TiO₅, ZrO₂). These attributes combined with low CTE and density suggest viability for microwave substrates or electronic applications.</p>

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Crystallization behavior of 2MgO-2Al₂O₃-3.33B₂O₃ glass with optimal dielectric properties and reduced thermal expansion

  • 期刊论文

  • 发表日期：

    2025年12月12日

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  • Haya Alhummiany,
  • Gehan T. El-Bassyouni,
  • Samah S. Eldera,
  • Esmat M.A. Hamzawy

摘要

Crystallization of the prepared transparent 2MgO-2Al₂O₃-3.33B₂O₃ glass system into a well glass-ceramic with optimized crystalline phases that simultaneously improve dielectric properties and lower thermal expansion (CTE) for enhanced functional performance. Despite its chemical equivalence to cordierite stoichiometry (2MgO-2Al₂O₃-5SiO₂), the investigated composition completely substitutes SiO₂ with B₂O₃. The nucleation efficiency of individual (TiO₂, ZrO₂) and combined TiO₂-ZrO₂ additives was rigorously evaluated. The glass-ceramics developed in this work exhibit tailored physicochemical properties (density, hardness, CTE, dielectric properties). Differential thermal analysis (DTA) identified a high crystallization (773–794 °C) for TiO₂-ZrO₂-doped formulations. Phase evolution studies confirmed the crystallization of kotoite (Mg3B2O6), sinhalite (MgAlBO4), aluminum borate (Al₄B₂O₉), baddeleyite (ZrO₂), and aluminum titanate (Al₂Ti₇O₁₅) at 800–900 °C. The SEM analysis of 900 °C-treated samples revealed a microstructure of submicron rod-like crystallites dispersed in a residual glass phase. Thermo-mechanical characterization yielded CTEs of 12.42–27.55 × 10⁻⁷ °C⁻¹ (25–300 °C) and 22.45–39.19 × 10⁻⁷ °C⁻¹ (25–400 °C). The glass-ceramics (density: 2.54–2.65 g/cm³; hardness: 5.42–5.85 GPa) exhibited superior dielectric properties (high dielectric constant, low dielectric loss) relative to parent glasses (2.61–2.73 g/cm³; 5.11–5.89 GPa), attributable to TiO₂/ZrO₂-derived crystalline phases (Al₂TiO₅, ZrO₂). These attributes combined with low CTE and density suggest viability for microwave substrates or electronic applications.