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<p>SnO₂–La₂O₃ composite powders containing 1, 3, 5, 7, and 10&#xa0;wt% nominal La₂O₃ were prepared by a sol–gel-assisted precipitation–dispersion route and examined to determine how phase constitution, surface oxygen chemistry, and microstructural heterogeneity affect the dielectric response. Preformed La₂O₃ powder was dispersed in an oxidized Sn precursor before alkaline precipitation; this process produced a Sn-rich hydroxide/oxyhydroxide precursor containing a La-derived oxide/hydroxide component and generated a composite architecture rich in phase-boundary and surface-oxygen heterogeneity. X-ray diffraction showed rutile-type tetragonal SnO₂ as the dominant phase throughout the series. The nonlinear composition dependence of lattice parameters and unit-cell volume, together with the stable principal SnO₂ Raman maximum at 626.7&#xa0;cm<sup>−1</sup>, confirms preservation of the rutile SnO₂ vibrational framework while indicating La-induced local disorder and phase-boundary modification. FE-SEM/EDX mapping showed La distributed across the analysed micrometre-scale fields and revealed composition-dependent particle-contact development. FT-IR and XPS consistently indicated increasing contributions from hydroxylated, hydrated, and carbonate-containing surface environments as the nominal La₂O₃ content increased. At 1&#xa0;kHz, the dielectric constant increased from 11.137 ± 0.092 for SnO₂ to 15.993 ± 0.064 for Sn-10La₂O₃, whereas tan<i>δ</i> remained within 0.065–0.070. A Lichtenecker logarithmic volume-mixture benchmark predicted <i>ε</i>′ = 11.472 for the 10&#xa0;wt% composition; the measured value was 39.4% higher than this ideal-mixture estimate. This positive excess permittivity verifies a non-ideal composite dielectric response and supports interfacial/electrical heterogeneity as the origin of the enhancement. The nearly composition-invariant loss-peak position, located in the same intermediate-frequency interval on the order of 104&#xa0;Hz, indicates that the dominant effective relaxation time remains approximately unchanged, while La<sub>2</sub>O<sub>3</sub> mainly increases the relaxation strength and low-frequency polarization amplitude. The response is therefore assigned to a distributed polarization process involving grain and particle contacts, phase-boundary electrical heterogeneity, electrode interfacial contributions, and hydration-sensitive surface polarization. Within the measured frequency window, Sn-7La₂O₃ and Sn-10La₂O₃ provide the most effective balance between enhanced permittivity and controlled dissipation, establishing La₂O₃-modified SnO₂ as a composition-tunable oxide dielectric platform for capacitor-oriented and frequency-sensitive ceramic components.</p>

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Composition-dependent ınterfacial polarization in La2O3-modified SnO2 composite ceramics: structure, surface hydroxylation, and broadband dielectric response

  • 期刊论文

  • 发表日期：

    2026年7月18日

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  • Melek Güner,
  • Cevher Kursat Macit,
  • Ezgi Gurgenc,
  • Merve Ayık,
  • Betül Çiçek Özkan,
  • Bünyamin Aksakal,
  • Turan Gurgenc

摘要

SnO₂–La₂O₃ composite powders containing 1, 3, 5, 7, and 10 wt% nominal La₂O₃ were prepared by a sol–gel-assisted precipitation–dispersion route and examined to determine how phase constitution, surface oxygen chemistry, and microstructural heterogeneity affect the dielectric response. Preformed La₂O₃ powder was dispersed in an oxidized Sn precursor before alkaline precipitation; this process produced a Sn-rich hydroxide/oxyhydroxide precursor containing a La-derived oxide/hydroxide component and generated a composite architecture rich in phase-boundary and surface-oxygen heterogeneity. X-ray diffraction showed rutile-type tetragonal SnO₂ as the dominant phase throughout the series. The nonlinear composition dependence of lattice parameters and unit-cell volume, together with the stable principal SnO₂ Raman maximum at 626.7 cm−1, confirms preservation of the rutile SnO₂ vibrational framework while indicating La-induced local disorder and phase-boundary modification. FE-SEM/EDX mapping showed La distributed across the analysed micrometre-scale fields and revealed composition-dependent particle-contact development. FT-IR and XPS consistently indicated increasing contributions from hydroxylated, hydrated, and carbonate-containing surface environments as the nominal La₂O₃ content increased. At 1 kHz, the dielectric constant increased from 11.137 ± 0.092 for SnO₂ to 15.993 ± 0.064 for Sn-10La₂O₃, whereas tanδ remained within 0.065–0.070. A Lichtenecker logarithmic volume-mixture benchmark predicted ε′ = 11.472 for the 10 wt% composition; the measured value was 39.4% higher than this ideal-mixture estimate. This positive excess permittivity verifies a non-ideal composite dielectric response and supports interfacial/electrical heterogeneity as the origin of the enhancement. The nearly composition-invariant loss-peak position, located in the same intermediate-frequency interval on the order of 104 Hz, indicates that the dominant effective relaxation time remains approximately unchanged, while La2O3 mainly increases the relaxation strength and low-frequency polarization amplitude. The response is therefore assigned to a distributed polarization process involving grain and particle contacts, phase-boundary electrical heterogeneity, electrode interfacial contributions, and hydration-sensitive surface polarization. Within the measured frequency window, Sn-7La₂O₃ and Sn-10La₂O₃ provide the most effective balance between enhanced permittivity and controlled dissipation, establishing La₂O₃-modified SnO₂ as a composition-tunable oxide dielectric platform for capacitor-oriented and frequency-sensitive ceramic components.