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Polarity-Dependent DC Dielectric Behavior of Virgin XLPO, XLPE, and PVC Cable Insulations
(2025-10-01)
Ruangwong, Khomsan
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Pattanadech, Norasage
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Pannil, Pittaya
Reliable DC cable insulation is crucial for photovoltaic (PV) systems and high-voltage DC (HVDC) networks. However, conventional materials such as cross-linked polyethylene (XLPE) and polyvinyl chloride (PVC) face challenges under prolonged DC stress—notably space charge buildup, dielectric losses, and thermal aging. Cross-linked polyolefin (XLPO) has emerged as a halogen-free, thermally stable alternative, but its comparative DC performance remains underreported. Methods: We evaluated the insulations of virgin XLPO, XLPE, and PVC PV cables under ±1 kV DC using time-domain indices (IR, DAR, PI, Loss Index), supported by MATLAB and FTIR. Multi-layer cable geometries were modeled in MATLAB to simulate radial electric field distribution, and Fourier-transform infrared (FTIR) spectroscopy was employed to reveal polymer chemistry and functional groups. Results: XLPO exhibited an IR on the order of 108–109 Ω, and XLPE (IR ~ 108 Ω) and PVC (IR ~ 107 Ω, LI ≥ 1) at 60 s, with favorable polarization indices under both polarities. Notably, they showed high insulation resistance and low-to-moderate loss indices (≈1.3–1.5) under both polarities, indicating controlled relaxation with limited conduction contribution. XLPE showed good initial insulation resistance but revealed polarity-dependent relaxation and higher loss (especially under positive bias) due to trap-forming cross-linking byproducts. PVC had the lowest resistance (GΩ-range) and near-unit DAR/PI, dominated by leakage conduction and dielectric losses. Simulations confirmed a uniform electric field in XLPO insulation with no polarity asymmetry, while FTIR spectra linked XLPO’s low polarity and PVC’s chlorine content to their electrical behavior. Conclusions: XLPO outperforms XLPE and PVC in resisting DC leakage, charge trapping, and thermal stress, underscoring its suitability for long-term PV and HVDC applications. This study provides a comprehensive structure–property understanding to guide the selection of advanced, polarity-resilient cable insulation materials.
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The role of γ-C2H5NO2 as a new transient liquid phase in cold sintering process of BaTiO3 composites
(2024-07-01)
Noisak, Jitrawan
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Ieamviteevanich, Pimchanok
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Charoonsuk, Thitirat
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Pakawanit, Phakkhananan
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Pinpru, Nattapong
Dielectric materials, such as barium titanate (BT)-based materials, have excellent dielectric properties but require high temperatures (above 1300 °C) for ceramic fabrication, leading to high costs and energy loss. The cold sintering process (CSP) offers a solution to these issues and is gaining worldwide attention as an innovative fabrication route. In this work, we proposed an alternative organic ferroelectric phase, gamma-glycine (γ-GC), which acts as a transient liquid phase to fabricate high-density composites with barium titanate (BT) at low temperatures through CSP. Our findings show that the density of 15γ-GC/85BT reached 96.7%±1.6% when it was sintered at 120 °C for 6 h under 10 MPa uniaxial pressure. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) mappings of the composite suggested that γ-GC completely underwent the precipitation–dissolution process and, therefore, filled between BT particles. Moreover, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirmed the preservation of γ-GC without undesired phase transformation. In addition, the ferroelectric and dielectric properties of γ-GC/BT composites have been reported. The high dielectric constant (ε<inf>r</inf>) was 3600, and the low dielectric loss (tanδ) was 1.20 at 200 °C and 100 kHz for the 15γ-GC/85BT composite. The hysteresis loop showed a remanent polarization (P<inf>r</inf>) of 0.55 µC·cm-2 and a coercive field (E<inf>c</inf>) of 7.25 kV·cm-1. Our findings reaffirmed that an organic ferroelectric material (γ-GC) can act as a transient liquid phase in a CSP that can successfully and sustainably fabricate γ-GC/BT composites at low temperatures while delivering outstandingly high performance.
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Sintering Temperature Effect on Phase Formation, Microstructure and Electrical Properties of Modified KNLNTS Solid Solution Prepared via the Solid-State Combustion Technique
(2023-01-01)
Kornphom, Chittakorn
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Thawong, Pichittra
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Khiwoon, Suprakorn
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Vittayakorn, Naratip
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Bongkarn, Theerachai
In this study, the effect of sintering temperature (1000–1100 °C for 2 h) on phase formation, phase transition, microstructure and electrical properties of lead-free piezoelectric (K<inf>0.44</inf>Na<inf>0.52</inf>Li<inf>0.04</inf>)(Nb<inf>0.84</inf>Ta<inf>0.10</inf>Sb<inf>0.06</inf>)O<inf>3</inf> (KNLNTS) solid solution with 0.3 wt%Bi<inf>2</inf>O<inf>3</inf> + 0.4 wt%Fe<inf>2</inf>O<inf>3</inf> + 0.2 wt%CuO additive (abbreviate as modified KNLNTS) was investigated. Modified KNLNTS ceramics were synthesized by the solid-state combustion technique using glycine as fuel. The modified KNLNTS powders were prepared using the calcination condition of 650 °C for 2 h. The XRD pattern of all sintered ceramics exhibited a pure perovskite phase. Using Rietveld refinement to analyze the phase formation showed that the modified KNLNTS ceramics had co-existing phases of orthorhombic and tetragonal in all sintered ceramics and the orthorhombic phase increased when the sintering temperature increased. The average grain size, T<inf>O-T</inf>, T<inf>c</inf>, P<inf>r</inf> and Ec increased with increasing sintering temperature. At the sintering temperature of 1025 °C, the modified KNLNTS ceramic showed the best electrical properties (C<inf>ε</inf> ≈ 6745, S<inf>max</inf> ≈0.274% and d*<inf>33</inf> ≈ 548 pm/V). The good electrical properties of the modified KNLNTS ceramics makes them good candidates for lead-free applications to replace Pb-based ceramics.
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Simple and Effective Design Concept for Constructing In-Situ Soil Dielectric Property Sensor with Dual Low-Cost COTS Microwave Modules
(2022-01-01)
Leekul, Prapan
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Mgawe, Bonny
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Kazema, Twahir
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Dao, Hoang Nam
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Sirisuk, Phaophak
This paper presents a compact sensor system for estimating the dielectric properties of materials based on commercial, off-the-shelf (COTS) modules. The dielectric constant and conductivity of a material under test can be determined from the measurement of the microwave reflected from the material. By using dual microwave sensor modules with a slightly different radio frequency, an identical intermediate frequency at the mixers of the modules was obtained. The intermediate frequency was chosen such that the associated microwave and data processing components could be easily obtainable, leading to a practical realization of the sensor system. Synchronization of the two microwave sensor modules was achieved using electronically controlled relays that simultaneously switch on the power supplies of both modules. Two microcontrollers were used to capture the corresponding signals. The sensor was designed at a 10 GHz band for measuring reflected waves from various kinds of materials, especially soils with different moisture and fertilizer contents. The evaluation results indicate a good agreement between the measured results from the proposed sensor and the ones from a network analyzer, verifying that the proposed sensor is fully functional for monitoring variation in the dielectric properties of materials, including soil. The average sensitivity for the dielectric constant of moist soil is 0.26/% moisture content and the error rate for dielectric constant measurement is 4.83%.
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Phase evolution, microstructure and electrical response of KNNT ceramics with Li+ substitution and doping
(2022-01-01)
Yotthuan, Surirat
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Udeye, Thanya
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Prasertpalichat, Sasiphon
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Pulphol, Phieraya
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Vittayakorn, Naratip
Lead-free (K<inf>0.5</inf>Na<inf>0.5</inf>)(Nb<inf>0.7</inf>Ta<inf>0.3</inf>)O<inf>3</inf> (KNNT) ceramics with Li+ substitution (KN<inf>0.5-x</inf>Li<inf>x</inf>NT) and direct (KNNT-xLi) doping at x = 0, 0.01, 0.02, 0.03 and 0.04 mol% were synthesized by the solid-state combustion route. The phase, microstructure, dielectric and ferroelectric properties of the ceramics were examined. The XRD pattern of the ceramics revealed orthorhombic and tetragonal phases in all specimens. The Rietveld refinement procedure showed that increasing either the Li+ substitution or doping levels enhanced the amount of the tetragonal phase. It was found that Li+ doping, either substitutional or additional, enhanced the Curie temperature (T <inf>C</inf>) by increasing the tetragonal distortion, while the dielectric constant (ε <inf>C</inf>) decreased. The good remanent P-E loops of the KN<inf>0.5-x</inf>Li<inf>x</inf>NT ceramics were found with x = 0.01 (P <inf>r</inf>∼10.89 µC/cm2 and E <inf>C</inf>∼13.09 kV/cm), while for KNNT-xLi ceramics, it was obtained with x = 0.02 (P <inf>r</inf>∼15.65 µC/cm2 and E <inf>C</inf>∼11.46 kV/cm), which were confirmed by remanent P-E hysteresis measurements.
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Improvement of phase structure and energy storage properties of [(0.72-x)Bi0.5Na0.5TiO3-0.28SrTiO3-xBaZr0.05Ti0.95O3] lead-free ceramics
(2022-01-01)
Panpho, Phakakorn
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Thongmee, Navavan
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Mathrmool, Krailas
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Unruan, Muangjai
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Vitayakorn, Narathip
Lead-free [(0.72-x)Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf>-0.28SrTiO<inf>3</inf>-xBaZr<inf>0.05</inf>Ti<inf>0.95</inf>O<inf>3</inf>] ceramics (abbreviated as BNT-ST-xBZT), x = 0, 0.03, 0.05, 0.07, 0.10, and 0.15 wt.%, were prepared by conventional solid-state reaction method. The effect of x(BZT) content on phase structure, microstructure, dielectric, ferroelectric, and energy storage properties of BNT-BT-x(BST) ceramics was studied. The samples of the study were analyzed through X-ray diffraction (XRD). The XRD patterns were analyzed using Rietveld refinement. The XRD revealed a single-phase perovskite for all the samples with coexisting rhombohedral and tetragonal phases. It shows the increasing of x(BZT) content and, more tetragonal distortion of the phase. The scanning electron micrographs (SEM) of all the samples displayed spherical-like morphology. The grain growth inhibited by increasing of x(BZT) content. The average of grain size decreased from 2.74 µm to 0.65 µm with BZT content. The highest density (ρ = 5.31 ± 0.11 g/cm3), recoverable energy storage density (W <inf>rec</inf> = 0.234 J/cm3), and energy storage efficiency (η = 90%) at 30 kV/cm were found in the composition of x(BZT) = 0.05 wt.%.
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Wideband dielectric properties of silicon and glass substrates for terahertz integrated circuits and microsystems
(2021-05-01)
Chudpooti, Nonchanutt
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Duangrit, Nattapong
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Burnett, Andrew D.
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Freeman, Joshua R.
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Gill, Thomas B.
This paper presents a comprehensive study of the optical and electrical dielectric material properties of six commonly-used silicon and glass substrates at terahertz (THz) frequencies, including refractive index, absorption coefficient, dielectric constant and loss factor. The material characterization techniques used in this paper feature THz time-domain transmission and reflection spectroscopy with the measurement frequencies from 0.5 THz up to a maximum of 6.5 THz. Of the six selected dielectric and semiconductor substrates, two are silicon wafers with resistivities ranging from 0.001 to 0.02 Ω-cm. From the measurement results, loss tangents of the selected silicon wafers range from 0.680 to 5.455 and the dielectric constants are from 1.079 to 17.735. The four other wafers are all glass-based substrates: D263 glass, Borofloat 33 glass, fused silica and Sapphire. From the measurements, it is found that the THz dielectric properties vary considerably between the substrate samples e.g. dielectric constants range from 1.925 to 3.207 while loss tangents are from 0.042 × 10-3 to 0.127. Most of the selected silicon and glass-based substrates are quite useful for many THz applications, e.g., THz integrated circuits (THz ICs), THz microsystem technologies (THz MSTs) and THz system-on-a-chip (THz SoC) and system-on-substrate (SiP).
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Effect of BFCO Doping on Phase Structure, Microstructure, Electric and Magnetic Properties of BNKLT Ceramics Prepared by the Combustion Method
(2021-01-01)
Thawong, Pichittra
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Bongkarn, Theerachai
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Jantasurin, Jirawat
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Pinitsoontorn, Supree
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Charoonsuk, Thitirat
Lead free solid solution Bi<inf>0.5</inf>(Na<inf>0.68</inf>K<inf>0.22</inf>Li<inf>0.10</inf>)<inf>0.5</inf>TiO<inf>3</inf>-xmol%Bi<inf>2</inf>FeCrO<inf>6</inf> (BNKLT-xBFCO), with x = 0, 0.004, 0.007, 0.013 and 0.019, ceramics were calcined at 750 °C and sintered at 1150 °C for 2 h using the solid state combustion technique. The effect of the x content on the phase formation, microstructure, electric and magnetic properties of the produced ceramics were investigated. All samples exhibited a pure perovskite phase with the co-existence of rhombohedral and tetragonal phases. The doping of BFCO enhanced the density and dielectric properties of the BNKLT ceramics. The BNKLT-0.013BFCO ceramics showed the highest density (5.87 g/cm3), excellent dielectric properties (ε <inf>R</inf> ∼1390, tan δ <inf>R</inf> ∼0.039, ε <inf>m</inf> ∼4986 and tan δ <inf>m</inf> ∼0.075) and the highest piezoelectric constant (d<inf>33</inf>∼194 pC/N). The sample with x = 0 showed diamagnetic behavior, while the samples with 0.004-0.019 content exhibited paramagnetic behavior with higher magnetization at higher x content.
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Synthesis and Characterization of KNN Modified BNT-ST Ceramics for Energy Storage Applications
(2021-01-01)
Thongmee, Navavan
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Klaytae, Thanawat
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Vittayakorn, Naratip
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Bongkarn, Theerachai
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Sumang, Rattiphorn
Lead-free [(0.76-x)Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf>–0.24SrTiO<inf>3</inf>–x(K<inf>0.5</inf>Na<inf>0.5</inf>)NbO<inf>3</inf>; BNT-ST-KNN] ceramics with x = 0, 0.03, 0.05, 0.07, 0.10, 0.15 wt.% were synthesized by using a solid-state reaction method. The effect of x content on phase, microstructure electrical and energy density properties was investigated. The samples were analyzed by X-ray diffraction (XRD) and the XRD patterns were fitted using the Rietveld refinement. The grain growth is obviously inhibited and smaller grains are formed in the ceramic samples at a high concentration of x. Dielectric study confirmed relax or nature with a drastic decrease of T <inf>max</inf> with the increase of x content in BNT-ST-KNN system. The maximum density (ρ = 5.42 (Formula presented.) 0.13 g/cm3), highest dielectric constant (ε<inf>r</inf> =3300) with tanδ∼0.05, high recoverable energy storage density (W <inf>rec</inf>=0.16 J/cm3) with energy storage efficiency of (η = 64) were obtained in x = 0.03 wt.% ceramic samples, which suggested its usefulness for energy-storage capacitor applications.
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Effect of Firing Conditions on Phase Formation, Microstructure, and Electrical Properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 Ceramics Synthesized by Solid-State Combustion Method
(2020-10-01)
Yotthuan, Surirat
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Charoonsuk, Thitirat
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Vittayakorn, Naratip
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Thountom, Sarawut
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Suriwong, Tawat
The effect of the firing conditions on the phase formation, microstructure, and electrical properties of (K<inf>0.5</inf>Na<inf>0.5</inf>)(Nb<inf>0.7</inf>Ta<inf>0.3</inf>)O<inf>3</inf> (KNNT) ceramics synthesized by the solid-state combustion technique using glycine as fuel has been investigated. All samples were calcined at 600°C to 800°C for 2 h and sintered at 1150°C to 1190°C for 2 h to 5 h. Pure KNNT powders were produced after calcination at 600°C for 2 h. The average particle size increased when the calcination temperature was increased. The KNNT powder calcined at 600°C for 2 h showed rather square morphology with average particle size of ∼ 160 nm. The x-ray diffraction (XRD) analysis results for the ceramics revealed the presence of orthorhombic (O) and tetragonal (T) phases in all samples. When sintering at 1150°C for 4 h, the O:T ratio was 50:50, as verified by the Rietveld refinement technique. The average grain size, density values, and dielectric properties tended to increase when the dwell time was increased from 2 h to 4 h, but then degraded. The KNNT ceramic produced at the optimum firing condition (1150°C for 4 h) showed good crystalline morphology, the highest density (ρ = 5.28 g/cm3), the highest dielectric constant (ε<inf>C</inf> = 5002), and good ferroelectric behavior (P<inf>r</inf> = 18.50 μC/cm2 and E<inf>c</inf> = 9.04 kV/cm).

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