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<p>Niobium pentoxide (Nb₂O₅) is an attractive dielectric oxide for electronic applications due to its high polarizability and thermal stability; however, its dielectric response is strongly influenced by processing-induced microstructural and phase variations. In the present work, the influence of compaction pressure on phase formation, microstructure, and dielectric behavior of Nb₂O₅ ceramics was systematically investigated. Pellets prepared from commercial Nb₂O₅ powder were uniaxially compacted at 150, 200, and 250&#xa0;MPa and sintered in air at 900&#xa0;°C for 2&#xa0;h. Phase evolution was examined using X-ray diffraction, while density and microstructural features were analyzed by Archimedes’ method and scanning electron microscopy, respectively. Dielectric properties were evaluated as a function of frequency (100&#xa0;Hz–1&#xa0;MHz) at room temperature and temperatures (35–400&#xa0;°C) at selected frequencies. XRD analysis confirmed the dominant Nb₂O₅ phase in all samples, with the presence of minor conductive sub-oxide phases (NbO₂ and Nb₁₂O₂₉) arising from high-temperature processing. Compaction pressure was found to significantly affect densification and microstructure, with the specimen compacted at 200&#xa0;MPa exhibiting the highest relative density (~ 78%) and a comparatively uniform grain morphology. Correspondingly, this sample showed enhanced dielectric constant values over the investigated frequency range, while all compositions exhibited typical dielectric dispersion with increasing frequency. Temperature-dependent measurements revealed an initial increase in capacitance and electrical conductivity up to approximately 235&#xa0;°C, followed by a decline at higher temperatures, attributed to thermally activated charge transport and phase-related effects. Dielectric loss remained low at high frequencies but increased markedly at low frequencies and elevated temperatures, indicating defect- and hopping-assisted conduction mechanisms. The results demonstrate that compaction pressure plays a critical role in governing phase stability, microstructure, and dielectric response of Nb₂O₅ ceramics processed at moderate sintering temperatures, providing useful insights for processing optimization in dielectric ceramic applications.</p>

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Influence of Compaction Pressure on Phase Formation and Dielectric Response of Nb₂O₅ Ceramics

  • 期刊论文

  • 发表日期：

    2026年5月28日

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  • Mahesh Tummala,
  • Brahma Raju Golla

摘要

Niobium pentoxide (Nb₂O₅) is an attractive dielectric oxide for electronic applications due to its high polarizability and thermal stability; however, its dielectric response is strongly influenced by processing-induced microstructural and phase variations. In the present work, the influence of compaction pressure on phase formation, microstructure, and dielectric behavior of Nb₂O₅ ceramics was systematically investigated. Pellets prepared from commercial Nb₂O₅ powder were uniaxially compacted at 150, 200, and 250 MPa and sintered in air at 900 °C for 2 h. Phase evolution was examined using X-ray diffraction, while density and microstructural features were analyzed by Archimedes’ method and scanning electron microscopy, respectively. Dielectric properties were evaluated as a function of frequency (100 Hz–1 MHz) at room temperature and temperatures (35–400 °C) at selected frequencies. XRD analysis confirmed the dominant Nb₂O₅ phase in all samples, with the presence of minor conductive sub-oxide phases (NbO₂ and Nb₁₂O₂₉) arising from high-temperature processing. Compaction pressure was found to significantly affect densification and microstructure, with the specimen compacted at 200 MPa exhibiting the highest relative density (~ 78%) and a comparatively uniform grain morphology. Correspondingly, this sample showed enhanced dielectric constant values over the investigated frequency range, while all compositions exhibited typical dielectric dispersion with increasing frequency. Temperature-dependent measurements revealed an initial increase in capacitance and electrical conductivity up to approximately 235 °C, followed by a decline at higher temperatures, attributed to thermally activated charge transport and phase-related effects. Dielectric loss remained low at high frequencies but increased markedly at low frequencies and elevated temperatures, indicating defect- and hopping-assisted conduction mechanisms. The results demonstrate that compaction pressure plays a critical role in governing phase stability, microstructure, and dielectric response of Nb₂O₅ ceramics processed at moderate sintering temperatures, providing useful insights for processing optimization in dielectric ceramic applications.