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    A novel lanthanum hexaboride-modified cementitious composites: evolution and microstructural architecture of LaB6-integrated GFRC systems with enhanced dielectric response
    (Elsevier Ltd, 2026) Demir, Ahmet; Subaşı, Serkan; Dehgan, Haydar; Ramazanoğlu, Doğu; Maraşlı, Muhammed; Aksu, Mecit; Gencel, Osman; Musatat, Ahmad Badreddin; Subaşı, Azime
    This study investigates the integration of lanthanum hexaboride (LaB6) microparticles into glass fiber-reinforced concrete (GFRC) to improve its dielectric and microstructural properties. GFRC mixtures with 1–3 % LaB6 replacement were characterized for capacitance, impedance, dielectric constant (ε′ and ε″), dissipation factor (tanδ), electrical modulus (M′ and M″), and Cole-Cole diagrams across varying frequencies (20 Hz–5 MHz) and hydration times (7–58 days). Comprehensive Microstructural, Thermal Stability, and Chemical Characterization analyses were also performed. Results demonstrate that LaB6 significantly improves GFRC's capacitance, conductivity, and dielectric properties. Specifically, L2 and L3 samples exhibited capacitance values approximately 100 times higher than the reference and L1 samples after 56 days, and approximately 25 times greater capacitance behavior across the tested frequency spectrum. The real dielectric constant (ε′) reached 250-fold, decreasing by about 10 times with LaB6 addition in L2 and L3, indicating improved insulation. Dielectric losses (ε″) were also markedly higher for L2 and L3, approaching 100 times greater than R and L1, implying favorable conductive functionality. Cole-Cole analysis indicated minimal dielectric dispersion for L2 and L3, suggesting near-ideal polarizable interfaces. Equivalent circuits were fitted, demonstrating that LaB6 significantly influences the electrical transport and storage mechanisms within the GFRC composites, leading to improved dielectric performance. Scanning electron microscopy (SEM) revealed denser microstructures, while thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Fourier-transform infrared spectroscopy (FTIR) corroborated enhanced thermal stability, bond strength, and favorable microstructural interactions. These findings highlight LaB6 as a promising additive for developing high-performance cementitious composites with tailored electrical responses for smart concrete applications.