Quaternary polycrystalline (CeLa)1−xSmxB6 ceramics fabricated by spark plasma sintering via borothermal reduction method
Journal of the Australian Ceramic Society, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Basım Tarihi: 2026
- Doi Numarası: 10.1007/s41779-026-01432-y
- Dergi Adı: Journal of the Australian Ceramic Society
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Anahtar Kelimeler: Borothermal reduction, Electrical properties, Microstructural development, Rare earth hexaborides, Solid solutions, Spark plasma sintering
- Hakkari Üniversitesi Adresli: Evet
Özet
Quaternary polycrystalline bulk (CeLa)1−xSmxB6 ceramics (x = 0, 0.1, 0.2, and 0.3) are fabricated by spark plasma sintering using a two-step-heating schedule at 1000 °C and 1950 °C. In-situ synthesis is achieved through borothermal reduction of rare earth oxide (REO) and elemental boron (B) starting powders in optimized ratios. This study aims to investigate the influence of Sm substitution on the phase evolution, microstructural development, and mechanical and electrical properties of the sintered ceramics. The materials are characterized using XRD, SEM/EDS, microstructural image analysis, microhardness testing, and electrical resistivity measurements. The results indicate that all sintered ceramics possess a dense matrix consisting of a single-phase REB6 solid solution. Sm doping leads to an increase in lattice distortion, with the lattice parameter shifting from 4.1348 to 4.1501 Å. Furthermore, this promotes the borothermal reduction, which enhances chemical purity by suppressing the formation of REO solid solutions and B secondary phases that otherwise remain as unconsumed grains within the microstructure. The minimization of secondary phases and the solid solution hardening effect contribute to the microhardness. The room-temperature electrical resistivity increases by two orders of magnitude, rising from 10− 6 to 10− 4 Ω⋅m at 30% Sm doping, attributed to the mixed-valence state of the Sm ions, which significantly reduces the concentration of conduction electrons. Consequently, (Ce0.35La0.35Sm0.30)B6 ceramics emerge as promising candidates for thermionic applications, specifically as directly heated cathodes, due to their single-phase REB6 solid solution structure, dense microstructure, high phase purity (97%), relatively high microhardness (∼17.8 GPa), and elevated electrical resistivity (10− 4 Ω⋅m).