scholarly journals Electrical properties of Nb/Al-doped CuO-based ceramics for NTC thermistors

2020 ◽  
Vol 14 (1) ◽  
pp. 47-55
Author(s):  
Xianchi Wang ◽  
Zhicheng Li ◽  
Weiqin Yan ◽  
Pinji Wang ◽  
Hong Zhang
Keyword(s):  
Electrical Properties ◽  
Photoelectron Spectroscopy ◽  
Boundary Effect ◽  
Sol Gel ◽  
Complex Impedance ◽  
Negative Temperature ◽  
Impedance Analysis ◽  
B Value ◽  
Polaron Hopping ◽  
Ntc Thermistors

Nb/Al-modified CuO ceramics (yNb/0.02Al-CuO, 0 ? y ? 0.07, denoted as NACO) were synthesized using sol-gel method for applications in negative temperature coefficient (NTC) thermistors. The phase structure, microstructure and electrical properties of the ceramics were investigated. XRD investigation reveals that the NACO ceramics has the main phase with monoclinic crystalline structure. The analysis of X-ray photoelectron spectroscopy proved the existence of Cu2+/Cu+ and Nb5+/Nb4+ ions. Temperature dependence of the resistivity indicated that the NACO ceramics present typical NTC characteristic. The NTC materials? constant, B value, can be adjusted from 2430K to 3805K by changing the Nb-concentration in the Al-doped CuO ceramics. Among four applied calibration equations the Hoge-3 equation is the most effective one for the resistancetemperature calibration of the prepared NTC thermistors. The complex impedance analysis was performed and revealed that both grain effect and grain boundary effect similarly contribute to the electrical conductive behaviour and NTC feature of the NACO ceramics. The band conduction and polaron hopping conduction are proposed as the conduction mechanisms in the NACO thermistors.

Grain boundary effects in NTC-PTC composite thermistor materials

1999 ◽  
Vol 14 (1) ◽  
pp. 120-123 ◽  
Author(s):  
D. J. Wang ◽  
J. Qiu ◽  
Y. C. Guo ◽  
Z. L. Gui ◽  
L. T. Li
Keyword(s):  
Energy Level ◽  
Grain Boundary ◽  
Boundary Effect ◽  
Complex Impedance ◽  
Negative Temperature ◽  
Impedance Analysis ◽  
Composite Effect ◽  
Complex Impedance Analysis ◽  
Temperature Coefficient Of Resistivity ◽  
Grain Boundary Effect

Yttrium-doped (Sr0.45Pb0.55)TiO3 ceramics have been studied by complex impedance analysis. As a sort of NTC-PTC composite thermistor, it exhibited a significantly large negative temperature coefficient of resistivity below Tc in addition to the ordinary PTC characteristics above Tc. It is found that the NTC effect in NTC-PTC materials was not originated from the deep energy level of donor (bulk behavior), but from the electrical behavior of the grain boundary. Therefore, the NTC-PTC composite effect was assumed to be a grain boundary effect, and yttrium was a donor at shallow energy level. The NTC-PTC ceramics were grain boundary controlled materials.

Synthesis, Structure and Electrical Properties of Pr-Doped Apatite-Type Lanthanum Silicates

2015 ◽  
Vol 1094 ◽  
pp. 155-159
Author(s):  
Li Peng Tian ◽  
Zhi Hua Ren
Keyword(s):  
Electrical Properties ◽  
Sol Gel ◽  
Complex Impedance ◽  
Impedance Analysis ◽  
Total Conductivity ◽  
X Ray Diffraction ◽  
Complex Impedance Analysis ◽  
Sol Gel Process ◽  
Lanthanum Silicates ◽  
Apatite Type

Apatite-type lanthanum silicates doped with Pr3+ at the La site, La10-xPrxSi6O27 (x = 0, 1, 2, 3, 4, 4.5), were synthesized via sol-gel process. Thermal behavior of the dried gel of La10-xPrxSi6O27 sample was studied using TG/DTA. X-ray diffraction, SEM and complex impedance analysis were used to investigate the microstructure and electrical properties of La10-xPrxSi6O27 ceramics. The XRD results indicated the maximum doping quantity of Pr3+ is x = 4.5. Lanthanum silicates doped with Pr3+ cations have a higher total conductivity than that of undoped lanthanum silicates. The enhanced total conductivity depends on the improved density of La10-xPrxSi6O27 (x = 0, 1, 2, 3, 4, 4.5). At 973K, the highest total conductivity is 1.36×10-3S.cm-1 for La9PrSi6O27 ceramic.

scholarly journals Impedance spectroscopy studies on lead free (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 ceramics

2012 ◽  
Vol 6 (4) ◽  
pp. 201-207 ◽  
Author(s):  
Ahcène Chaouchi ◽  
Sadia Kennour
Keyword(s):  
High Temperature ◽  
Impedance Spectroscopy ◽  
Grain Boundary ◽  
Boundary Effect ◽  
Complex Impedance ◽  
Negative Temperature ◽  
Polycrystalline Sample ◽  
Impedance Analysis ◽  
Wide Frequency Range ◽  
Nyquist Plot

The AC complex impedance spectroscopy technique has been used to obtain the electrical parameters of polycrystalline sample of (Ba0.85Ca0.15) (Ti0.9Zr0.1)O3 in a wide frequency range at different temperatures. This sample was prepared by a high temperature solid-state reaction technique and single phase formation was confirmed by X-ray diffraction technique. This study was carried out by the means of simultaneous analysis of impedance, modulus, and electrical conductivity. The Cole-Cole (Nyquist) plots suggest that the grains and grain boundaries are responsible in the conduction mechanism of the material at high temperature. The Cole- Cole (Nyquist) plot studies revealed the presence of grain and grain boundary effect at 485 ?C. On the other hand, it showed only the presence of grain boundary component of the resistivity at 535 ?C. Complex impedance analysis indicated the presence of non-Debye type dielectric relaxation. The bulk resistance of the material decreases with rise in temperature similar to a semiconductor, and the Cole-Cole (Nyquist) plot showed the negative temperature coefficient of resistance (NTCR) character of (Ba0.85Ca0.15 )(Ti0.9Zr0.1 )O3. The value of activation energy is found to be 0.7433 eV, which suggests that the conduction may be the result of defect and charge carriers present in the materials.

STRUCTURAL AND IMPEDANCE CHARACTERISTICS OF KPb2V5O15

2011 ◽  
Vol 25 (28) ◽  
pp. 3745-3753
Author(s):  
P. S. DAS ◽  
P. K. CHAKRABORTY ◽  
BANARJI BEHERA ◽  
R. N. P. CHOUDHARY
Keyword(s):  
Boundary Effect ◽  
Complex Impedance ◽  
Negative Temperature ◽  
Polycrystalline Sample ◽  
Homogeneous Distribution ◽  
Orthorhombic Crystal ◽  
Ac Electrical Conductivity ◽  
Orthorhombic Crystal Structure ◽  
Impedance Characteristics ◽  
Sem Micrograph

The polycrystalline sample of KPb 2 V 5 O 15 was prepared by a mixed-oxide method relatively at low temperature (i.e., 550°C). X-ray diffraction studies of the compound showed the formation of single phase orthorhombic crystal structure at room temperature. SEM micrograph showed the homogeneous distribution of grains throughout the sample. Electric properties were analyzed using the complex impedance spectroscopy. The modulus plot showed the presence of both the grain and grain boundary effect. The bulk impedance evaluated from the Nyquist plots was observed to decrease with the rise in temperature, showing a negative temperature coefficient of resistance. The variation of AC electrical conductivity (σ AC ) was measured in a wide temperature (30–500°C) and frequency (102–106 Hz) range. The activation energy of the compound calculated from both the impedance and modulus spectrum was found to be the same.

scholarly journals The Effect of Fe and Mn Substitution on Structural and Electrical Properties of LaCoO3 Nanoparticles

2019 ◽  
Vol 8 (6) ◽  
pp. 3213-3217
Keyword(s):  
Chemical Composition ◽  
Electrical Properties ◽  
Sol Gel ◽  
Impedance Analysis ◽  
Structure And Morphology ◽  
Edax Analysis ◽  
Structural And Electrical Properties ◽  
Fe And Mn ◽  
Mn Substitution ◽  
Mn Doped

Pure and Fe, Mn doped LaCoO3 nanoparticles are primed by sol gel ignition method, and their electrical properties are studied. All the materials were characterized to study the structure and morphology. The chemical composition of the samples was analysed by EDAX analysis revealing that La, Co, O (Mn, Fe) compounds were present. Electrical properties were identified in impedance analysis and the conductivity of the materials was calculated. And it is found that Fe doped LaCoO3 possesses higher conductivity than all others

scholarly journals Effect of Heat Treatment on Structural, Magnetic and Electrical Properties of La2FeMnO6

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7501
Author(s):  
Djoko Triyono ◽  
Y Yunida ◽  
Rifqi Almusawi Rafsanjani
Keyword(s):  
Heat Treatment ◽  
Electrical Properties ◽  
Calcination Temperature ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Phonon Modes ◽  
Magnetic Exchange ◽  
X Ray ◽  
Treatment Conditions ◽  
Magnetic And Electrical Properties

In this study, the effect of heat treatment on the structural, magnetic and electrical properties of La2FeMnO6 prepared via the sol–gel and sintering method were investigated. The heat-treatment conditions, i.e., the calcination temperature (1023 K and 1173 K), sintering temperature and time (1273 K for 1 and 3 h) were carried out. X-ray diffraction (XRD) revealed orthorhombic pnma (62) symmetry without any impurity phase for all samples. X-ray photoelectron spectroscopy confirmed the presence of Fe2+–Fe3+–Fe4+ and Mn3+–Mn4+ mixed states, and lanthanum and oxygen vacancies resulting in various magnetic exchange interactions. Furthermore, the magnetisation hysteresis showed enhanced hysteresis loops accompanied by an increase in magnetisation parameters with calcination temperature. The Raman phonon parameters induced a redshift in the phonon modes, alongside an increase in the intensity and compression of the linewidth, reflecting a decrease in lattice distortion, which was confirmed by XRD. The temperature-dependent conductivity showed that the conduction mechanism is dominated by p-type polaron hopping, and the lowest activation energy was approximately 0.237 ± 0.003 eV for the minimum heat-treatment conditions. These results show that varying heat-treatment conditions can significantly affect the structural, magnetic and electrical properties of the La2FeMnO6 system.

scholarly journals Grain boundary effects on piezoelectric properties of the core–shell-structured BaTiO3@TiO2 ceramics

2018 ◽  
Vol 08 (06) ◽  
pp. 1850044 ◽  
Author(s):  
Xixi Li ◽  
Zhonghua Yao ◽  
Juan Xie ◽  
Zongxin Li ◽  
Hua Hao ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Boundary Effect ◽  
Ferroelectric Properties ◽  
Critical Role ◽  
Impedance Analysis ◽  
Ferroelectric Materials ◽  
Boundary Effects ◽  
Grain Boundary Effects ◽  
Grain Boundary Effect

Grain boundary effect on BaTiO3 has been widely investigated for several decades. However, all of them tailored the grain boundary by grain size of BaTiO3. In this case, a direct way was introduced to modify the grain boundary by coating technique to investigate the role of grain boundary in ferroelectric materials. Nonferroelectric phase TiO2 was employed to investigate grain boundary effects on the electrical properties of BaTiO3 piezoelectric ceramics. TiO2 coating can result in the reduction of piezoelectric and ferroelectric properties and the annealing process in oxygen can increase piezoelectric behavior of pure BaTiO3 due to valence state of Ti ions while that remains for Ti-modified composition possibly due to the increased grain boundary effect by impedance analysis. Compared with ferroelectric grain, grain boundary plays a critical role to impact the electrical properties of perovskite-type ferroelectric materials.

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