Structural, cation distribution, thermal properties, and electrical resistivity of nano NiAlxFe2-xO4 synthesized by flash auto combustion method

2021 ◽  
pp. 131273
Author(s):  
Enas A. Arrasheed ◽  
Yamen A. Alibwaini ◽  
T.M. Meaz ◽  
Rizk Mostafa Shalaby ◽  
B.I. Salem ◽  
...  
2015 ◽  
Vol 29 (26) ◽  
pp. 1550151 ◽  
Author(s):  
B. Rajesh Babu ◽  
K. V. Ramesh ◽  
M. Sivaram Prasad ◽  
Y. Purushotham

Nanocrystalline Ni–Zn–Al spinel ferrite was synthesized via citrate-gel auto combustion method. The as-prepared powders have been separated into two batches in which one batch of powders were sintered at 1000[Formula: see text]C for 4 h and the other batch were pressed into pellets and were sintered at the same temperature. Sintering of the samples was done in air atmosphere followed by natural cooling to room temperature. The heat treated powders have then been characterized using TG–DTA, XRD, SEM and TEM for thermal, structural and microstructural aspects while the DC electrical resistivity measurements were carried out on the sintered pellets. The X-ray diffraction patterns displayed the formation of the spinel phase for all powders and the lattice parameter was obtained using Bragg’s law. The crystallite size for all compositions were found to be in nano dimensions and obtained from the Williamson–Hall method. TG–DTA analysis of the undoped [Formula: see text] indicated the formation of the spinel phase is around 400[Formula: see text]C while almost uniform microstructure with a more or less spherical grains has been noticed in the SEM micrograph. An enhancement in the DC electrical resistivity ([Formula: see text]-cm) has been observed in [Formula: see text] synthesized using this technique in comparison with that processed through conventional ceramic technique and a modification in the resistivity has been observed on substituting [Formula: see text] in place of [Formula: see text]. High electrical resistivity makes these ferrites suitable for high-frequency applications due to possible reduction of the eddy current losses. The observed variation in resistivity has been discussed on amendments in structure, microstructure and unavailability of [Formula: see text] ions with increasing [Formula: see text] ions in the light of existing understanding. The decrease in resistivity with increasing temperature confirms the semiconducting behavior of all samples. Activation energies for conduction were obtained from the slope of the log [Formula: see text] versus [Formula: see text] plots and observed to be in the range of 0.6–0.45 eV. The variation in the activation energy for conduction followed a similar trend as the DC resistivity. The drift mobility decreases with increasing [Formula: see text] ions concentration and increases with increasing temperature.


2020 ◽  
Vol 5 (3) ◽  
pp. 236-251
Author(s):  
Eshwara I. Naik ◽  
Halehatty S.B. Naik ◽  
Ranganaik Viswanath

Background: Various interesting consequences are reported on structural, optical, and photoluminescence properties of Zn1-xSmxO (x=0, 0.01, 0.03 and 0.05) nanoparticles synthesized by sol-gel auto-combustion route. Objective: This study aimed to examine the effects of Sm3+-doping on structural and photoluminescence properties of ZnO nanoparticles. Methods: Zn1-xSmxO (x=0, 0.01, 0.03 and 0.05) nanoparticles were synthesized by sol-gel auto combustion method. Results: XRD patterns confirmed the Sm3+ ion substitution through the undisturbed wurtzite structure of ZnO. The crystallite size was decreased from 24.33 to 18.46 nm with Sm3+ doping. The hexagonal and spherical morphology of nanoparticles was confirmed by TEM analysis. UV-visible studies showed that Sm3+ ion doping improved the visible light absorption capacity of Sm3+ iondoped ZnO nanoparticles. PL spectra of Sm3+ ion-doped ZnO nanoparticles showed an orange-red emission peak corresponding to 4G5/2→6HJ (J=7/2, 9/2 and 11/2) transition of Sm3+ ion. Sm3+ ion-induced PL was proposed with a substantial increase in PL intensity with a blue shift in peak upon Sm3+ content increase. Conclusion: Absorption peaks associated with doped ZnO nanoparticles were moved to a longer wavelength side compared to ZnO, with bandgap declines when Sm3+ ions concentration was increased. PL studies concluded that ZnO emission properties could be tuned in the red region along with the existence of blue peaks upon Sm3+ ion doping, which also results in enhancing the PL intensity. These latest properties related to Sm3+ ion-doped nanoparticles prepared by a cost-efficient process appear to be interesting in the field of optoelectronic applications, which makes them a prominent candidate in the form of red light-emitting diodes.


2015 ◽  
Vol 241 ◽  
pp. 226-236 ◽  
Author(s):  
Neha Solanki ◽  
Rajshree B. Jotania

Influence of Ca substitution on structural, magnetic and dielectric properties of Ba3Co2-xCaxFe24O41(where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), prepared by Sol-Gel auto-combustion method, has been investigated in present studies. The obtained powder was sintered at 950 oC for 4 hrs. in the static air atmosphere. Structural analysis of Ca-doped Ba3Co2-xCaxFe24O41powders revealed pure Z-type hexaferrite phase at low temperature. The frequency dependent dielectric constant (Єʹ) and magnetic properties such as remanent magnetization (Mr), saturation magnetization (Ms) and coercivity (Hc) were studied. It is observed that coercivity increased gradually with increase in calcium content. The real dielectric constant (Єʹ) and dielectric loss tangent (tan δ) were studied in the frequency range of 20Hz to 2MHz. The dielectric parameters for all samples show normal dielectric behavior as observed in hexaferrites. Contents of Paper


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