الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
During the last decade ABO3 manganites with
perovskite structure exhibit a widely studying due to its
physical, magnetic and electric properties that improve
their various applications like sensors, catalysts electrode
materials for solid-oxide fuel cell. This work concerns on
studying: 1) the effect of various cation substitution such
as Ca and Sr cations on phase and microstructural of
LaMnO3 phase and 2) the role of these cation on
changing electrical, physical and magnetic properties of
such material. Two different ways of preparation have
been applied i.e. a hydrothermal method and mechanical
activation method in this work. In hydrothermal
synthesis, the crystalline powder can be prepared in one
step from solutions of metal salts at a temperature of 230
°C in 48 h. On other hand, the mechanical activation
method are carried out by preparation the metal oxides
depending on using manganese oxide that were extracted
from low-grade ores by using glucose as a reducing agent
in dilute nitric acid. Then the prepration of perovskite
manganite samples by milling and mixing the reactant
metal oxides with the extracted MnO2 has been carried
out and then added to other various oxides to prepare
manganite compounds. In all the samples the Perovskite
manganites have been prepared in a general formula
LaxCa1-xMnO3 and LaxSr1-xMnO3 (x = 0.1, 0.3, 0.5 and
1.00) and then sintered at different temperatures ranging
from 1100oC to 1450oC. The powder characteristics of
metal-doped lanthanum manganites are characterized
utilizing x-ray diffraction to elucidate the phase
transformation, scanning electron microscopy (SEM),
transmission electron microscopy (TEM) and selected
area electron diffraction (SAED) were used to elucidate
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the size and morphology of the particles and crystalline
structure of these powders. For hydrothermal procedures
the results revealed that the maximum sintering
temperature for LCMO is 1400oc while for LSMO is
1450oc. XRD patterns show that the pervoskite phase is
detected at 2θ at 33-34. By addition of Ca2+ and Sr2+ the
peaks are shifted to lower 2θ. SEM micrographs of all
grains are rod like shape. The magnetic properties of
hydrothermally prepared samples are detected, where the
magnetization of perovskite samples is improved by the
addition of Ca2+ and Sr2 and the highest results are
observed for La0.5Ca0.5MnO3 and La0.5Sr0.5MnO3. For
mechanical activation method, MnO2 is obtained by
leaching method at 95ºC and characterized by XRD.
Studying the bulk density and apparent porosity show that
the sintering temperature of LCMO samples is 1300 oC
while for LMO and LSMO is 1350oC. TEM images of an
individual La0.1Ca0.9MnO3 nanoparticles and
La0.1Sr0.9MnO3 nanoparticles exhibits single-crystalline
particles. XRD results for sintered samples prepared by
mechanosynthesis show that perovskite phases are
prepared after 8 h of milling with sharp peaks at 2θ
ranged between 32-34 that shifted to lower 2θ values by
the substitution of La 3+ with Ca2+ and Sr2+. Scanning
electron microscopy (SEM) morphology for the sintered
samples appears in spherical shapes. The grain sizes are
different for LCMO and LSMO samples according to x
values. For magnetic properties, LSMO samples have
higher magnetization than LMO and LCMO samples.
La0.5Sr0.5MnO3 exhibits higher magnetization than the
others. The electrical resistivity for both producers shows
that LCMO samples are higher than LSMO samples due
to their different atomic size, while LaMnO3 exhibits the
highest resistivity