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Dielectric and electrochemical behavior of hydrothermally synthesized Zn-doped titanate nanotubes
(2026-11-01)
Masakul, Pristanuch
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Krongkitsiri, Pacharee
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Thongbai, Prasit
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Kidkhunthod, Pinit
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Maensiri, Santi
A bstract Zn-doped titanate nanotubes (Zn-doped TNTs) with the composition of Zn<inf>x</inf>Ti<inf>3-x</inf>O<inf>7</inf>, (Na<inf>0.96</inf>H<inf>1.04</inf>∙3.42H<inf>2</inf>O) (where x = 0, 0.05, 0.1, and 0.2) were synthesized via a hydrothermal method at 130 °C for 24 h. Structural and morphological characterization using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-Vis (Ultraviolet-Visible), X-ray Absorption Near Edge Structure (XANES), and Brunauer-Emmett-Teller (BET) techniques confirmed the formation of well-defined nanotubes with controlled dimensions. Transmission electron microscopy (TEM) images of undoped and Zn-doped titanate nanotubes reveal uniform hollow nanotubular structures with diameters of ∼7–15 nm and multilayered walls. The dielectric properties of the Zn-doped TNTs were examined using an LCR meter across a frequency range of 102–106 Hz. The results revealed a remarkably high dielectric constant (ε′) (∼104-105 at 30 °C and 1 kHz), which was attributed to Debye-like relaxation governed by Maxwell-Wagner polarization. The dielectric response exhibited a strong dependence on Zn doping levels, with higher Zn content leading to enhanced permittivity. Electrochemical properties were evaluated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The Zn-doped TNTs demonstrated a specific capacitance ( C ) of 23 F g−1 at a scan rate of 1 mV s−1, indicating their potential for energy storage applications. This systematic investigation of Zn incorporation provides critical insights into its impact on the structural, dielectric, and electrochemical properties of titanate nanotubes (TNTs). These findings provide useful insight for further optimization of doped titanate nanostructures toward advanced multifunctional dielectric and electrochemical energy-storage applications.
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Effect of quenching technique on electrical properties of KNN ceramics
(2026-05-01)
Sompong, Khanisorn
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Kaewsit, Sriwan
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Parjansri, Piewpan
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Pengpat, Kamonpan
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Yongsiri, Ploypailin
Cooling rate during sintering constitutes a critical yet systematically underexplored processing variable that governs defect thermodynamics, microstructural evolution, and functional performance in lead-free K<inf>0.5</inf>Na<inf>0.5</inf>NbO<inf>3</inf> (KNN) piezoelectric ceramics. This study establishes quantitative processing-structure-property relationships by systematically comparing two contrasting post-sintering thermal trajectories controlled slow cooling (S-SC) and rapid quenching (S-Q) across sintering temperatures of 1050-1130 °C. Phase-pure KNN ceramics were synthesized via conventional solid-state reaction incorporating 3 mol% excess alkali carbonates and subsequently sintered for 3 h. Structural and microstructural characterization was conducted by X-ray diffraction, scanning electron microscopy, and Archimedes bulk density measurements. Dielectric and ferroelectric responses were evaluated as functions of both sintering temperature and cooling protocol. S-SC processing at 1130 °C yielded synergistic microstructural improvements bulk density of 4.33 g/cm3 (+12.5% relative to 1050 °C), XRD-derived crystallinity of 62% (+24%), and mean grain size of 11.44 μm, that collectively suppressed point-defect concentration through three concurrent mechanisms: elimination of pore-associated extrinsic defect sites, reduction of intrinsic oxygen vacancies (V_O••) via extended thermally activated annihilation, and diminished grain boundary area available for preferential defect segregation. These microstructural advances directly translated into superior dielectric permittivity (εᵣ = 350 at 1 kHz) and remanent polarization (Pᵣ = 0.65 μC/cm2). Conversely, S-Q processing kinetically arrested oxygen vacancy migration and preserved metastable high-temperature domain configurations, yielding competitive permittivity (εᵣ = 242) and enhanced thermal stability at moderate sintering temperatures (1080 - 1100 °C), despite comparatively reduced crystallinity and bulk density. Both thermal protocols preserved the orthorhombic perovskite structure; however, the optimum cooling strategy is demonstrably temperature-dependent. The present findings provide a mechanistic defect-thermodynamic framework and evidence-based thermal processing guidelines for the rational design of high-performance lead-free KNN-family piezoelectric ceramics.
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Electrical and magnetic properties of BSFO-NZF multiferroic composite ceramics
(2025-06-01)
Kaewsit, Sriwan
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Sompong, Khanisorn
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Pairindra, Worapong
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Pengpat, Kamonpan
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Yongsiri, Ploypailin
This study involves the characterization and synthesis of (1-x)Bi<inf>0.9</inf>Sm<inf>0.1</inf>FeO<inf>3</inf> (BSFO) in association with (x)Ni<inf>0.6</inf>Zn<inf>0.4</inf>Fe<inf>2</inf>O<inf>4</inf> (NZF) multiferroic composite ceramics, utilizing x ratios of 0.0, 0.1, 0.3, 0.5, 0.7, and 1.0, achieved through the high-energy planetary ball milling technique and conventional solid-state reaction method. X-ray diffraction confirms the formation of perovskite in the BSFO phase and spinel cubic structure in the NZF phase, absent from any elemental residues. It also signifies the successful incorporation of Sm ions into the BFO lattice. The utilization of field emission scanning electron microscopy (FESEM) combined with energy dispersive X-ray spectroscopy (EDX) for microstructural analysis demonstrates densified structures resulting from reduced grain sizes with the incorporation of NZF and verifies the composition percentages in the BSFO/NZF composite ceramic. The investigation of ferroelectric materials revealed that the ceramic hysteresis loop for the conditions of x = 0.3 and x = 0.5 demonstrated the most optimal ferroelectric behavior. The dielectric constant (ε<inf>r</inf>) exhibited composition-dependent behavior, decreasing from 4895.32 to 44.64 at 1 kHz with increasing NZF content, while demonstrating consistent frequency dispersion across 1 kHz to 1 MHz. Magnetic measurements conducted via vibrating sample magnetometry revealed a substantial increase in saturation magnetization from 0.24 emu/g to 80.06 emu/g as NZF concentration increased, under a maximum applied field of 20 kOe. Enhanced magnetic properties with preserved ferroelectricity enable potential magnetoelectric device applications. This study establishes systematic composition-property relationships that offer insights for optimizing multiferroic composites in practical applications such as sensors, actuators, and data storage devices.
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Investigation into the impedance, dielectric behavior, and conductivity within p-silicon/n-nanocrystalline iron disilicide heterojunctions and equivalent circuit model in relation to temperature
(2025-03-15)
Borwornpornmetee, Nattakorn
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Sittimart, Phongsaphak
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Traiprom, Thawichai
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Paosawatyanyong, Boonchoat
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Yoshitake, Tsuyoshi
The p-Si/n-nanocrystalline FeSi<inf>2</inf> heterojunctions constructed through facing-targets sputtering were characterized for impedance under various frequencies and temperatures of between 160−400 K. Imaginary and real impedance plots for all temperatures demonstrated single semicircular arc with negative temperature dependency. From the arc, a circuit model equivalent to electrode resistance serially connected to several loops, each consisting of a parallel circuit comprising a resistance//constant phase element (Q), corresponding to the crystallite, crystallite boundary, and interface. All resistances increased with decreasing temperatures, while the Q values decreased but behaved as ideal capacitors for all temperatures. The dielectric constants versus increasing temperature demonstrated a linear increase. At 300 K and 1 MHz, the dielectric constant was 24.5 with 0.1 loss tangent, denoting its possible usage for filtration and storage. The alternating-current conductivities disclosed that direct-current conductivities increased as the temperature increased. The exponents from Jonscher's fit were 1 or less around 180 K and the values beyond 1 at higher temperatures, indicating the shift from long transitional transport to localized hopping transport. The activation energy based on conductivities was higher than the one based on relaxation times, implying that excess charge led to more energy requirements for transportation.
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Improved dielectric properties of PVDF polymer composites filled with Ag nanomaterial deposited reduced graphene oxide (rGO) hybrid particles
(2022-01-01)
Tuichai, Wattana
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Karaphun, Attaphol
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Ruttanapun, Chesta
We report a method to improve the dielectric constant (ε′) of polyvinylidene fluoride (PVDF) composites by using a low content of Ag nanomaterials deposited reduced Graphene Oxide (rGO) Hybrid Particles (Ag-rGO HPs). The Ag-rGO HPs are prepared by a reaction between silver nitrate and ethylene glycol in a seed-mediated growing process. The dispersion of Ag nanomaterials was completely homogeneous on the surface of rGO nanosheets with particle sizes of 5.765 ± 0.189 nm. The Ag-rGO HPs/PVDF composites were produced by a liquid–phase assisted dispersion and hot-pressing methods. The high ε′ at 103 Hz for Ag-rGO/PVDF composites with f<inf>Ag-rGO</inf> 7.8, and 11.9 vol% was 153 and 683, respectively. The best-fitting curve was completely achieved in percolation theory by adjusting f<inf>c</inf> = 14 vol%. The high ε′ (683 at 1 kHz) of Ag-rGO/PVDF could be explained by Maxwell Wagnare Sillars interfacial polarization and micro-capacitor due to the formation of a sandwich between Ag-rGO and PVDF.
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Structural, optical and electrical properties of the microcrystalline structure of (Ba1-xY2x/3)(Zr0.20Ti0.80)O3 ceramics
(2020-07-01)
Sumang, Rattiphorn
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Thongmee, Navavan
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Bongkarn, Theerachai
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Prasertpalichat, Sasipohn
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Kidkhunthod, Pinit
Yttrium (Y3+) doped barium zirconate titanate, (Ba<inf>1-x</inf>Y<inf>2x/3</inf>)(Zr<inf>0.20</inf>Ti<inf>0.80</inf>)O<inf>3</inf>; BYZT ceramics with varying x (0 = x ≤ 0.10) were prepared by the solid-state reaction method. These samples were analyzed by X-ray diffraction (XRD) and the XRD patterns were fitted using the Rietveld refinement. The local structural changes of the BYZT ceramics were investigated by synchrotron X-ray absorption spectroscopy. The results showed that an increase in the x content in the BYZT lattice structure significantly affected the phase transition behavior and the local structure around the Ti absorbing atoms, which corresponds with the phase transition from a tetragonal to a cubic structure. SEM images showed a uniform and highly dense microstructure with increasing x values. The optical band gap (E<inf>gap</inf>) values measured from the UV–visual diffuse reflectance spectra, showed a decrease from ~3.55 eV to ~2.90 eV with increasing values of x. The modified Curie-Weiss law showed that a normal ferroelectric phase transition is observed in the unmodified BZT ceramic and as the concentration of x increased, it induces diffuseness in the phase transition behavior. The largest dielectric constant (ε<inf>r</inf> = 13,200), the highest recoverable energy-storage density (W<inf>rec</inf> = 1.76 J/cm3) with an excellent energy storage efficiency (η = 91%) under a lower electric field of 50 kV/cm and lowest dielectric loss (tanδ = 0.01) were found in the composition of Ba<inf>0.98</inf>Y<inf>0.01337</inf>Zr<inf>0.2</inf>Ti<inf>0.8</inf>O<inf>3</inf> (x = 0.02 mol.%).

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