Infrared Emissivities and Microwave Absorption Properties of Perovskite La1-xCaxMnO3 (0≤x≤0.5)

2018 ◽  
Vol 914 ◽  
pp. 96-101 ◽  
Author(s):  
Jia Wei Liu ◽  
Jian Jiang Wang ◽  
Hai Tao Gao
Keyword(s):  
Electrical Conductivity ◽  
Sol Gel ◽  
Resistivity Measurement ◽  
Wave Band ◽  
Infrared Emissivity ◽  
Doping Amount ◽  
Microwave Absorbing Properties ◽  
Lanthanum Manganites ◽  
Microwave Absorbing ◽  
Perovskite Type

La1-xCaxMnO3(0≤x≤0.5) with perovskite-type structure has been successfully prepared by sol-gel method as a microwave and infrared multi-functional material. The effects of Ca incorporation on the stucture, electrical conductivity, infrared emissivity and microwave-absorbing properties were investigated in detail by XRD, 4-point probes resistivity measurement system,IR-2 infrared-emissivity analyzer and vector network analyzer. XRD results show that the perovskite structure of LaMnO3 is hardly changed when the doping concentration (x) of Ca2+ is less than or equal to 0.5. The incorporation of Ca in LaMnO3 leads to the decrease of electrical conductivity, while the infrared emissivities are decreased. Moreover, microwave-absorbing properties in the frequency range of 2-18 GHz are sensitive to Ca content. The optimal reflection loss calculated from the measured permittivity and permeability is 42 dB at 10.5 GHz with a thickness of 2.0 mm when the doping amount of Ca2+ is 0.1. It is possible to make Ca-doped lanthanum manganites achieve compatible camouflage capability for radar and infrared wave-band.

On the Sol-Gel Synthesis and Structure, Electronic and Ionic Conductivities and Impedance Behavior of Y, Fe Co-Doped SrTiO3 Mixed Conductor

2018 ◽  
Vol 281 ◽  
pp. 774-781
Author(s):  
Ke Shan ◽  
Feng Rui Zhai ◽  
Nan Li ◽  
Zhong Zhou Yi
Keyword(s):  
Electrical Conductivity ◽  
Ionic Conductivity ◽  
Ionic Conduction ◽  
Sol Gel ◽  
Ionic Conductivities ◽  
Wide Frequency Range ◽  
Mixed Conductor ◽  
Doping Amount ◽  
Impedance Characteristics ◽  
Sol Gel Synthesis

A single phase perovskite, YxSr1−xTi0.6Fe0.4O3-δ(x=0.06-0.09), was fabricated at 1350°C in air by sol-gel method. The effects of Y-and Fe-doping into SrTiO3on phase structure, electrical conductivity, ionic conductivity and its impedance behavior were investigated. The optimized Y0.07Sr0.93Fe0.4Ti0.6O3-δsample exhibits an electrical conductivity of 0.135 S·cm-1at 800 °C. Y-doping decreases the migration energy for oxygen ions, leading to a significant increase in ionic conductivity. The ionic conductivity of Y0.09Sr0.91Ti0.6Fe0.4O3-δsample varies from 0.0052 S· cm-1at 600°C to 0.02 S·cm-1at 800°C. Impedance characteristics over a wide frequency range of 0.01Hz-100 KHz reveal that the resistance of ionic conduction is predominantly influenced by grain boundary, the relaxation time of which decreases with increase of Y-doping amount.

Synthesis and microwave absorbing properties of La-doped Sr-hexaferrite nanopowders via sol–gel auto-combustion method

Rare Metals ◽  
2015 ◽  
Vol 36 (9) ◽  
pp. 704-710 ◽  
Author(s):  
Jun-Liang Liu ◽  
Peng Zhang ◽  
Xing-Kai Zhang ◽  
Qing-Qing Xie ◽  
Dong-Jun Pan ◽  
...  
Keyword(s):  
Sol Gel ◽  
Combustion Method ◽  
Microwave Absorbing Properties ◽  
Auto Combustion ◽  
Microwave Absorbing ◽  
La Doped

Microwave-absorbing properties of strontium ferrites prepared via sol-gel method

2017 ◽  
Vol 52 (5) ◽  
pp. 1700057 ◽  
Author(s):  
Liu Xing ◽  
Pan Shun-kang ◽  
Zhong Xing ◽  
Cheng Li-chun
Keyword(s):  
Sol Gel ◽  
Gel Method ◽  
Sol Gel Method ◽  
Microwave Absorbing Properties ◽  
Microwave Absorbing ◽  
Strontium Ferrites

Preparation, Microwave Absorption and Infrared Emissivity of Ni-doped ZnO/Al Powders by Coprecipitation Method in the GHz Range

NANO ◽  
2016 ◽  
Vol 11 (04) ◽  
pp. 1650047 ◽  
Author(s):  
Ruiwen Shu ◽  
Honglong Xing ◽  
Xiaoli Cao ◽  
Xiaoli Ji ◽  
Dexin Tan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Crystal Lattice ◽  
Photoelectron Spectroscopy ◽  
Impedance Match ◽  
Precipitation Method ◽  
Infrared Emissivity ◽  
X Ray ◽  
Microwave Absorbing Properties ◽  
Doped Zno ◽  
Microwave Absorbing

In this work, Ni-doped ZnO/Al composites were prepared by a facile chemical co-precipitation method. The morphology and structure of the as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that the flake-like Al powders were successfully coated by Ni-doped ZnO nanoparticles with slight aggregation and Ni[Formula: see text] was successfully doped into the crystal lattice of ZnO. Moreover, the effects of ZnO concentration and doped Ni concentration on the infrared emissivity of ZnO/Al composites at the waveband range of 8–14[Formula: see text][Formula: see text]m were studied. The results showed that the ZnO/Al composites exhibited the lowest infrared emissivity of 0.34 with 50[Formula: see text]wt.% ZnO concentration. Meanwhile, the electromagnetic parameters and microwave absorbing properties of Ni-doped ZnO/Al composites in the frequency range of 2–18[Formula: see text]GHz were explored. Significantly, 12[Formula: see text]mol.% Ni-doped ZnO/Al composites presented the lowest infrared emissivity of 0.37 and the maximum reflection loss reached [Formula: see text]32.5[Formula: see text]dB at 13.6[Formula: see text]GHz with a thickness of 4.5[Formula: see text]mm. The excellent microwave absorbing properties could be attributed to the good impedance match, crystal lattice defects and interfacial polarization. It was believed that the Ni-doped ZnO/Al composites could be used as potential infrared-microwave compatible stealth materials.

scholarly journals The low infrared emissivity of Ce1-xYxO2-x/2 samples at high-temperature contributed by enhanced conductivity

2018 ◽  
Vol 238 ◽  
pp. 03002
Author(s):  
Honghan Bu ◽  
Chuyang Liu ◽  
Guoyue Xu ◽  
Yong Jiang ◽  
Tengchao Guo ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Solid State Reaction Method ◽  
Potential Candidate ◽  
Aircraft Engines ◽  
Infrared Emissivity ◽  
Doping Amount ◽  
Reaction Method ◽  
Phase Structures ◽  
Increasing Temperature ◽  
Enhanced Conductivity

The Ce1-xYxO2-x/2 samples were synthesized with different doping amount by solid state reaction method. Phase structures of the samples were analyzed and characterized by XRD. The effects of different doping amount on infrared emissivity properties at 3-5µm wavebands were investigated systematically. It is found that the powder with doping molality of x=0.2 exhibits the lowest infrared emissivity value ca. 0.21 when the test temperature is 600 °C. The mechanism for the low infrared emissivity is explored thoroughly. The reduction of infrared emissivity with increasing temperature is ascribed to the enhancement of electrical conductivity. Our results suggest that Ce1-xYxO2-x/2 powder with x=0.2 is a potential candidate for stealth material of aircraft engines.

The microwave absorbing properties of La0.8K0.2MnO3 synthesized by sol–gel method

2016 ◽  
Vol 28 (2) ◽  
pp. 1168-1173 ◽  
Author(s):  
Shuang Zhao ◽  
Ji Zheng ◽  
Biao Shi ◽  
Lihua He ◽  
Zhongyi Liu
Keyword(s):  
Sol Gel ◽  
Gel Method ◽  
Sol Gel Method ◽  
Microwave Absorbing Properties ◽  
Microwave Absorbing

Comparison of Hollow-Porous and Solid Carbon Fibers as Microwave Absorbents

2010 ◽  
Vol 150-151 ◽  
pp. 1336-1342 ◽  
Author(s):  
Wei Xie ◽  
Hai Feng Cheng ◽  
Zeng Yong Chu ◽  
Zhao Hui Chen ◽  
Yong Jiang Zhou ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Carbon Fiber ◽  
Carbon Fibers ◽  
Porous Carbon ◽  
Fiber Composites ◽  
Carbon Fiber Composites ◽  
Solid Carbon ◽  
Microwave Absorbing Properties ◽  
Surface Electrical Conductivity ◽  
Microwave Absorbing

A series of polyacrylonitrile-based hollow-porous and solid carbon fibers were prepared by pyrolysis of polyacrylonitrile-based hollow-porous and solid fibers at the same condition. The microstructure, composition, surface electrical conductivity, electromagnetic parameters and reflectivity of carbon fibers were studied. The microwave absorbing properties of two kinds of carbon fibers as microwave absorbents were parallel investigated. Results show that the apparent density of the hollow-porous carbon fibers is lower than that of the solid carbon fibers due to their hollow-porous structure. The surface electrical conductivity of single solid carbon fiber is nearly 10 times that of the hollow-porous carbon fiber. The -10dB bandwidths of solid carbon fiber composites carbonized at 850 and 950°C are both 0GHz, while those of the corresponding hollow-porous carbon fiber composites are up to 3.05 and 2.62GHz, respectively. Results indicate that the microwave absorbing properties of the hollow-porous carbon fiber composites are better than those of solid carbon fiber composites.

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