Electrocatalytic performance of Pb−Ru pyrochlore prepared by the amorphous citrate precursor method for bifunctional air electrodes

2002 ◽  
Vol 8 (2) ◽  
pp. 215-219 ◽  
Author(s):  
Churl Kyoung Lee ◽  
Hun-Joon Sohn
Keyword(s):  
Precursor Method ◽  
Electrocatalytic Performance ◽  
Citrate Precursor ◽  
Citrate Precursor Method

COMPARATIVE STUDY OF DIELECTRIC BEHAVIOR OF Mn0.4Zn0.6Fe2O4 NANOFERRITE BY CITRATE PRECURSOR METHOD

2008 ◽  
Vol 22 (16) ◽  
pp. 2537-2544 ◽  
Author(s):  
PREETI MATHUR ◽  
ATUL THAKUR ◽  
M. SINGH
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Comparative Study ◽  
Average Particle Size ◽  
Dielectric Behavior ◽  
Average Particle ◽  
Oxidizing Agent ◽  
Precursor Method ◽  
Citrate Precursor ◽  
Citrate Precursor Method

In the present work, comparative study of the dielectric behavior of Mn 0.4 Zn 0.6 Fe 2 O 4 ferrite synthesized with and without H 2 O 2 (hydrogen peroxide) has been presented. The dc resistivity has been improved by the citrate precursor method as compared to the ceramic method, and it is further improved by the addition of H 2 O 2, which acts as a strong oxidizing agent. We have shown by means of X-ray diffraction that the resulting ferrite is made up of nanocrystallites and the average size of these nanocrystallites–calculated by Scherrer's formula–depends on the polarizer. The average particle size was found to be ~70 nm with H 2 O 2 and ~88 nm without H 2 O 2. The particle size is further confirmed by scanning electron microscopy. Both the results are found to be in good agreement. The decrease in dielectric constant and dielectric loss factor by addition of oxidizing agent is justified by inverse proportionality between the resistivity and dielectric constant. Possible mechanisms contributing to these processes have been discussed.

STRUCTURAL AND MAGNETIC PROPERTIES OF (R0.5A0.5)NIO3 PEROVSKITES (R = GD, YB AND A = CE, TH)

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3443-3447
Author(s):  
J. W. CHEN ◽  
H. M. LIU ◽  
H.-C. I. KAO ◽  
H. S. SHEU ◽  
J. F. LEE ◽  
...  
Keyword(s):  
Grain Size ◽  
Room Temperature ◽  
Unit Cell Volume ◽  
Bond Angle ◽  
Mixed Valence ◽  
Monoclinic Symmetry ◽  
Precursor Method ◽  
Structural And Magnetic Properties ◽  
Citrate Precursor ◽  
Citrate Precursor Method

Four perovskite compounds with nominal compositions of ( Gd 0.5 Th 0.5) NiO 3, ( Gd 0.5 Ce 0.5) NiO 3, ( Yb 0.5 Th 0.5) NiO 3 and ( Yb 0.5 Ce 0.5) NiO 3 were prepared by a polymeric citrate precursor method. They were either slow-cooled in the furnace or quenched to room temperature. All of them have monoclinic symmetry. Quenched samples have a slightly bigger unit cell volume and longer Ni-O bond length, and a smaller grain size than that of the furnace-cooled compounds. All samples are paramagnetic insulators in the range of 2 K to 300 K. The Th containing compounds have larger tolerance factor and Ni (1)– O (1)– Ni (2) bond angle than that of the Ce containing compounds. No mixed valence of Ce, Th and Ni is observed in these samples.

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