Study of microstructure, impedance and dc electrical properties of RuO2-spinel based screen printed ‘green’ NTC thermistor

Shweta Jagtap,Sunit Rane,Rohini Aiyer,Suresh Gosavi,Dinesh Amalnerkar 한국물리학회 2010 Current Applied Physics Vol.10 No.4

The NTC powder materials were prepared chemically using acetates of (Mn–Co–Ni), as precursor materials. The sintering of the powders shows the existence of spinel phases at comparatively low temperature,i.e. 800 ℃. ‘Green’ thick films were prepared by admixing of the spinel powder, RuO2, lead free glass frit and the organic vehicle. Synthesized powders as well as the thermistor films were characterised by FTIR spectroscopy, TG/DTA, XRD and SEM. The electrical parameters like sheet resistance, thermistor constant,temperature co-efficient of resistance of the thick film thermistors are presented. The impedance of the thermistor films was measured and it has been correlated with the theoretical model and its equivalent circuit using the ‘Cole–Cole’ plots.

Nondegenerate n-type doping phenomenon on molybdenum disulfide (MoS₂) by zinc oxide (ZnO)

Kang, D.H.,Hong, S.T.,Oh, A.,Kim, S.H.,Yu, H.Y.,Park, J.H. Pergamon Press 2016 Materials research bulletin Vol.82 No.-

<P>In this paper, we have demonstrated nondegenerate n-type doping phenomenon of MoS2 by ZnO. The ZnO doping effects were systematically investigated by Raman spectroscopy and electrical/optical measurements (I-D-V-G with/without exposure to 520, 655, 785, and 850 nm laser sources). The ZnO doping improved the performance parameters of MoS2-based electronics (Ion up arrow, mu(FE)up arrow, n up arrow) owing to reduction of the effective barrier height between the source and the MoS2 channel. We also monitored the effects of ZnO doping during exposure to air; reduction in Delta V-TH of about 75% was observed after 156 h. In addition, the optoelectronic performance of the MoS2 photodetector was enhanced due to the reduction of the recombination rate of photogenerated carriers caused by ZnO doping. In our results, the highest photoresponsivity (about 3.18 x 10(3) A/W) and detectivity (5.94 x 10(12) Jones) of the ZnO-doped photodetector were observed for 520 nm laser exposure. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Graphene oxide/poly(2-methylaniline) composite particle suspension and its electro-response

Sim, Bomi,Zhang, Wen Ling,Choi, Hyoung Jin Elsevier 2015 Materials chemistry and physics Vol.153 No.-

<P><B>Abstract</B></P> <P>Graphene oxide (GO)/poly(2-methylaniline) (P2MAN) composite particles were prepared by chemical oxidation polymerization and adopted as an electrorheological (ER) material. Because of its electrical conductivity originating from both semi-conducting P2MAN and GO, it could be tuned finely using P2MAN for ER applications. The morphology and chemical structure of the composite were examined by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The ER properties of the GO/P2MAN composite particles dispersed in silicone oil were examined with and without an applied electric field. The fibrillation phenomenon of this GO/P2MAN-based electro-responsive fluid was also observed by optical microscopy under an electric field. The flow curves and dynamic modulus of the GO/P2MAN suspension were measured by rotational rheometry under a range of electric field strengths, exhibiting typical ER characteristics and a slope of the dynamic yield stress of 1.5. GO appeared to improve the compatibility of the composite particles within the medium, which resulted in improved sedimentation stability compared to that of the P2MAN-based ER fluid.</P> <P><B>Highlights</B></P> <P> <UL> <LI> GO/P2MAN composite was fabricated by Hummers method and oxidation polymerization. </LI> <LI> The composite particles based fluid exhibited typical electrorheological properties. </LI> <LI> The fluid was correlated to conduction model and showed solid-like characters. </LI> <LI> GO was helpful to improve stability of fluid due to large surface area and compatibility. </LI> </UL> </P>

Surface characterization and material migration during surface modification of die steels with silicon, graphite and tungsten powder in EDM process

Anirban Bhattacharya,Ajay Batish,Naveen Kumar 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.1

The present study reports the results of an experimental work carried out to evaluate the improvement in machined surface properties of die steels machined using powder mixed electric discharge machining (PMEDM) process. Two surface responses, surface finish and microhardness were analyzed for changes when machined with Si, W and graphite powders mixed in dielectric fluid. The machined surfaces were subsequently analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to study the element migration from powder, dielectric and the tool. The powder mixed with dielectric and its concentration, current and pulse on time were identified as the significant factors affecting surface finish. Brass electrode and tungsten powder resulted in good surface finish. Amongst the dielectrics used, kerosene provided a better cooling effect whereas EDM oil resulted in better surface finish. The microhardness of the machined surface was also affected by powder and its concentration, current, pulse on time and electrode material. W-Cu electrode and W powder resulted in a higher microhardness. The SEM and EDS analysis showed significant migration of material from the suspended powder, electrode and dielectric to the machined surface.

Tetragonal-structural changes influenced the magnetic and ferroelectric properties of (Y, Fe)-codoped BaTiO3 ceramics

Choi Y.J.,Kim S.W.,Phan T.L.,Lee B.W.,Yang D.S. 한국물리학회 2023 Current Applied Physics Vol.53 No.-

We present a detailed study on the structural characterization, electronic structure, and magnetic/electric-polarization properties of Ba1-xYxTi1-xFexO3 (BYxTFxO, x = 0–0.1) ceramic samples. These samples mainly crystalized in a tetragonal structure, and a small amount of a YFeO3-related secondary phase constituted as x ≥ 0.08. With increasing x, the lattice constant a increases while c decreases. Such structural changes reduce rapidly the intensity of characteristic Raman modes. Magnetization data have proved all BYxTFxO samples exhibiting ferromagnetism at room temperature. Both the saturation magnetization and coercivity tend to increase with increasing x. This is ascribed to an enhanced exchange interaction between Fe3+ ions, and the YFeO3-phase formation. Herein, the Fe3+ presence has been confirmed upon analyzing X-ray absorption spectra. Though all the samples exhibit ferroelectricity, the electric-polarization slightly decreases with increasing x. This is associated with an increased symmetry due to the changes in the lattice parameters towards the cubic structure.

Investigation of AlInN HEMT structures with different AlGaN buffer layers grown on sapphire substrates by MOCVD

O. Kelekci,P. Tasli,S.S. Cetin,M. Kasap,S. Ozcelik,E. Ozbay 한국물리학회 2012 Current Applied Physics Vol.12 No.6

We investigate the structural and electrical properties of AlxIn1-xN/AlN/GaN heterostructures with AlGaN buffers grown by MOCVD, which can be used as an alternative to AlInN HEMT structures with GaN buffer. The effects of the GaN channel thickness and the addition of a content graded AlGaN layer to the structural and electrical characteristics were studied through variable temperature Hall effect measurements, high resolution XRD, and AFM measurements. Enhancement in electron mobility was observed in two of the suggested AlxIn1-xN/AlN/GaN/Al0.04Ga0.96N heterostructures when compared to the standard AlxIn1exN/AlN/GaN heterostructure. This improvement was attributed to better electron confinement in the channel due to electric field arising from piezoelectric polarization charge at the Al0.04Ga0.96N/GaN heterointerface and by the conduction band discontinuity formed at the same interface. If the growth conditions and design parameters of the AlxIn1-xN HEMT structures with AlGaN buffers can be modified further, the electron spillover from the GaN channel can be significantly limited and even higher electron mobilities, which result in lower two-dimensional sheet resistances, would be possible. We investigate the structural and electrical properties of AlxIn1-xN/AlN/GaN heterostructures with AlGaN buffers grown by MOCVD, which can be used as an alternative to AlInN HEMT structures with GaN buffer. The effects of the GaN channel thickness and the addition of a content graded AlGaN layer to the structural and electrical characteristics were studied through variable temperature Hall effect measurements, high resolution XRD, and AFM measurements. Enhancement in electron mobility was observed in two of the suggested AlxIn1-xN/AlN/GaN/Al0.04Ga0.96N heterostructures when compared to the standard AlxIn1exN/AlN/GaN heterostructure. This improvement was attributed to better electron confinement in the channel due to electric field arising from piezoelectric polarization charge at the Al0.04Ga0.96N/GaN heterointerface and by the conduction band discontinuity formed at the same interface. If the growth conditions and design parameters of the AlxIn1-xN HEMT structures with AlGaN buffers can be modified further, the electron spillover from the GaN channel can be significantly limited and even higher electron mobilities, which result in lower two-dimensional sheet resistances, would be possible.

Indigenous materials revolution: Synthesizing porcelain alumina ceramic insulators for sustainable electrical systems in Indonesia

W. Garinas,A. Fauzi,H. Hidayaturrahman,Q.N. Madra,Subari,D.M. Nurjaman,W. Hidayat,Y. Sudiyanto,N.V. Permatasari,Zulfahmi,Yurohman 한양대학교 청정에너지연구소 2024 Journal of Ceramic Processing Research Vol.25 No.2

The modern electrical industry in Indonesia faces escalating energy demands, projected to reach 1,413 Terawatt Hours by2060. Meeting these demands necessitates enhancing the quality of electrical transmission systems, particularly insulators, witha focus on local materials to reduce dependency on imports. Porcelain Alumina Ceramic Insulators (PACI) offer promisingalternatives due to their high resistivity and mechanical strength. This study investigates PACI synthesis using locally sourcedmaterials: kaolin, ball clay, alumina, and feldspar. Chemical analysis confirms alumina as the primary component (99.7%Al2O3), while other materials contribute to silica content. Fabrication involves crushing, drying, grinding, sieving, and sinteringat 1280 °C, yielding specimens (K1S, K2S, K3S). Material characterization employs XRD, XRF, SEM and electrical testsreveals phase compositions, morphological changes, and electrical properties. K3S, rich in feldspar, exhibits superior materialstrength (74.62 N/mm²) and hardness (190 N/mm²) with limited conductivity. Utilizing local resources for PACI productionpromises economic benefits and reduces import dependence. This study illuminates the interplay between material compositionand resulting properties, offering insights into ceramic synthesis for improved electrical infrastructure.

Electrical Properties of Dense and Nanocrystalline Sm^(3+)-Doped Ce_(1-x)Sm_xO_(2-δ) (0.05 ≤ x ≤ 0.3) Electrolytes for IT-SOFCs

K. Park,H. K. Hwang 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.3

Sm^(3+)-doped Ce_(1-x)Sm_xO_(2-δ) (0.05 ≤ x ≤ 0.3) nano-sized powders for solid electrolytes were synthesized by a solution combustion method, using aspartic acid as a combustion fuel. The calcined Ce_(1-x)Sm_xO_(2-δ) powders were a ceria-based single phase with a cubic fluorite structure. The nano-sized Ce_(1-x)Sm_xO_(2-δ) powders provided a high density, ultra-fine grain size, and high electrical conductivity even at a low sintering temperature of 1400 °C. The grain size and relative density of the Ce_(1-x)Sm_xO_(2-δ_ pellets ranged from 329 nm to 496 nm and from 91.9 % to 99.2 %, respectively. The grain size and density of the Ce_(1-x)Sm_xO_(2-δ) pellets decreased with an increase of Sm^(3+) content. The electrical conductivity of the Ce_(1-x)Sm_xO_(2-δ) increased with an increase of Sm^(3+) content up to x = 0.25 and then decreased with higher Sm^(3+) content. The maximal electrical conductivity (0.105 Scm^(−1)) was obtained with Ce_0.75Sm_0.25O_(2-δ) at 800 °C.

Effect of annealing temperature on the electrical and structural properties of V/p-GaN Schottky structures

Padma, R.,Nagaraju, G.,Rajagopal Reddy, V.,Choi, Chel-Jong Elsevier 2016 THIN SOLID FILMS - Vol.598 No.-

<P><B>Abstract</B></P> <P>The electrical and structural properties of V/p-GaN Schottky barrier diode (SBD) have been investigated as a function of annealing temperature. The Schottky barrier height (SBH) of the as-deposited contact is found to be 0.82eV (<I>I–V</I>) and 1.10eV (<I>C–V</I>). However, it is noted that the SBH increases for the contact annealed at 400°C and the values are 0.94eV (<I>I–V</I>) and 1.21eV (<I>C–V</I>). Further, with increasing annealing temperature up to 500°C, the SBH decreases to 0.92eV (<I>I–V</I>) and 1.19eV (<I>C–V</I>). Also, the rectification ratio of the V/p-GaN SBD is evaluated for as-deposited and annealed contacts. The electrical parameters of the V/p-GaN SBD are also discussed with Cheung's and Norde functions. It is noted that the interface state density decreases upon annealing at 400°C and then slightly increases after annealing at 500°C. Results reveal that the superior electrical characteristics are obtained for the contact annealed at 400°C. The electrical results are also correlated with the interfacial microstructure of the contacts. The AES and XRD results reveal that the formation of nitride phases at the interface may be the reason for the increase of SBH after annealing at 400°C. The formation of gallide phases at the interface may be reason for the decrease in the SBH.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Annealing effects on electrical and structural properties of V/p-GaN SBD are studied. </LI> <LI> Maximum barrier height is obtained on V/p-GaN SBD upon annealing at 400°C. </LI> <LI> Interface state density decreases with increasing annealing temperature up to 400°C. </LI> <LI> Electrical results are correlated with the interfacial microstructure of the contacts. </LI> <LI> Nitride interfacial phases are responsible for increase in BH after annealing at 400°C. </LI> </UL> </P>

Electrical properties of (Na_0.5Bi_0.5)(Zr_0.75Ti_0.25)O₃ ceramic

Lily, Lily,Yadav, K.L.,Prasad, K. Techno-Press 2013 Advances in materials research Vol.2 No.1

Lead-free compound $(Na_{0.5}Bi_{0.5})(Zr_{0.75}Ti_{0.25})O_3$ was prepared using conventional ceramic technique at $1070^{\circ}C$/4h in air atmosphere. X-ray diffraction analysis showed the formation of single-phase orthorhombic structure. Permittivity data showed low temperature coefficient of capacitance ($T_{CC}{\approx}5%$) up to $100^{\circ}C$. Complex impedance studies indicated the presence of grain boundary effect, non-Debye type dielectric relaxation and evidences of a negative temperature coefficient of resistance. The ac conductivity data were used to evaluate the density of states at Fermi level and apparent activation energy of the compound.