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<p>This work comparatively investigates the effects of conventional sintering (CS) and spark plasma sintering (SPS) on the microstructure and dielectric properties of diffuse ferroelectric BaTi<sub>0.85</sub>Zr<sub>0.15</sub>O<sub>3</sub> (BTZ15) ceramics. BTZ15 nanopowders were synthesized by solid-state reaction and mechanical milling, and densified either by CS at 1300 and 1400&#xa0;°C or by SPS at 1200&#xa0;°C, with selected SPS samples subsequently annealed at 1100&#xa0;°C in air to promote re-oxidation. Phase analysis by X-ray diffraction confirmed single-phase cubic perovskite ceramics for all processing routes, while scanning electron microscopy revealed a strong grain refinement from ~0.456 to 0.798&#xa0;μm in CS samples to ~199&#xa0;nm in SPS-ceramics. Dielectric spectroscopy of CS-BTZ15 showed a single broad permittivity maximum at <i>T</i><sub>m</sub> ~ 62&#xa0;°C, low dielectric loss (tan <i>δ</i> &lt; 0.06), and weak frequency dispersion, consistent with a diffuse ferroelectric phase transition. Modified Curie–Weiss analysis yielded <i>γ</i> ≈ 1.5 and enlarged diffuseness parameters. Impedance spectroscopy indicated highly insulating behavior with <i>ac</i> conductivities of 10<sup>−10</sup>–10<sup>−11</sup> S/cm. In contrast, the as-sintered SPS-ceramics exhibited giant permittivity (<i>ε′</i> &gt; 10<sup>5</sup>), very high dielectric loss, and conductivities of 10<sup>−2</sup>–10<sup>−1</sup> S/cm, attributable to oxygen-vacancy formation. Post-annealing of SPS-ceramics in air largely suppressed this defect-induced conduction and restored the insulating diffuse ferroelectric response. The annealed SPS-BTZ15 ceramics preserved the fine-grained microstructure, yielded enhanced permittivity relative to CS-BTZ15, and significantly reduced dielectric loss compared to as-sintered SPS-ceramics. These results demonstrate that SPS combined with appropriate re-oxidation enables effective grain-size control and defect engineering in BaTi<sub>0.85</sub>Zr<sub>0.15</sub>O<sub>3</sub>.</p>

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Spark plasma versus conventional sintering of diffuse ferroelectric BaTi0.85Zr0.15O3: microstructure and dielectric properties

  • 期刊论文

  • 发表日期：

    2026年4月8日

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  • Mohamad M. Ahmad,
  • Nagih M. Shaalan,
  • Abdullah Alshehab,
  • Hasna Abdullah Alali,
  • Latifah Alismail,
  • Hicham Mahfoz Kotb,
  • Hassan A. Khater

摘要

This work comparatively investigates the effects of conventional sintering (CS) and spark plasma sintering (SPS) on the microstructure and dielectric properties of diffuse ferroelectric BaTi0.85Zr0.15O3 (BTZ15) ceramics. BTZ15 nanopowders were synthesized by solid-state reaction and mechanical milling, and densified either by CS at 1300 and 1400 °C or by SPS at 1200 °C, with selected SPS samples subsequently annealed at 1100 °C in air to promote re-oxidation. Phase analysis by X-ray diffraction confirmed single-phase cubic perovskite ceramics for all processing routes, while scanning electron microscopy revealed a strong grain refinement from ~0.456 to 0.798 μm in CS samples to ~199 nm in SPS-ceramics. Dielectric spectroscopy of CS-BTZ15 showed a single broad permittivity maximum at Tm ~ 62 °C, low dielectric loss (tan δ < 0.06), and weak frequency dispersion, consistent with a diffuse ferroelectric phase transition. Modified Curie–Weiss analysis yielded γ ≈ 1.5 and enlarged diffuseness parameters. Impedance spectroscopy indicated highly insulating behavior with ac conductivities of 10−10–10−11 S/cm. In contrast, the as-sintered SPS-ceramics exhibited giant permittivity (ε′ > 105), very high dielectric loss, and conductivities of 10−2–10−1 S/cm, attributable to oxygen-vacancy formation. Post-annealing of SPS-ceramics in air largely suppressed this defect-induced conduction and restored the insulating diffuse ferroelectric response. The annealed SPS-BTZ15 ceramics preserved the fine-grained microstructure, yielded enhanced permittivity relative to CS-BTZ15, and significantly reduced dielectric loss compared to as-sintered SPS-ceramics. These results demonstrate that SPS combined with appropriate re-oxidation enables effective grain-size control and defect engineering in BaTi0.85Zr0.15O3.