Microstructure, Magnetic and Electrical Properties of La0.67(Sr1-Xbax)0.33 Mn1-Ytiyo3
A study on the microstructure, magnetic and electrical properties of La0.67Sr0.33MnO3 substituted with Ba at Sr site and Ti at Mn site have been performed. Samples of La0.67(Sr1-xBax)0.33 Mn1-yTiyO3 (LSBMT) with x = 0.00, 0.25, 0.50, 0.75 and 1.00; and y = 0.00, 0.05, 0.10, 0.15, 0.20, 0.40 and 0...
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my-upm-ir.75512013-05-27T07:35:33Z Microstructure, Magnetic and Electrical Properties of La0.67(Sr1-Xbax)0.33 Mn1-Ytiyo3 2009 Zainuddin, Zalita A study on the microstructure, magnetic and electrical properties of La0.67Sr0.33MnO3 substituted with Ba at Sr site and Ti at Mn site have been performed. Samples of La0.67(Sr1-xBax)0.33 Mn1-yTiyO3 (LSBMT) with x = 0.00, 0.25, 0.50, 0.75 and 1.00; and y = 0.00, 0.05, 0.10, 0.15, 0.20, 0.40 and 0.60 were prepared using solid state reaction method. Quantitative compositional percentage data of the elements results confirmed the expected La:Sr:Ba:Mn:Ti ratios for the prepared samples. X-ray Diffractometer (XRD) spectrum showed single phase compounds, except for samples with y = 0.60 which have La2Ti2O7 peaks. Sr substitution with Ba changed the rhombohedral R-3c structure to cubic Pm3m, however Mn substitution with Ti only increased the lattice parameters values, without changing the whole structure. Scanning Electron Microscope (SEM) images showed a few porous structured samples, with coarse and fine grains while the others showed large closely packed grains with clear shapes and grain boundaries. The magnetization studies showed that samples with y = 0.00 exhibited a transition from the ferromagnetic to the paramagnetic phase as temperature increased and the Curie temperature, TC decreased from 371 K to 341 K when x increased from 0.00 to 1.00. TC also decreased when y increased. Magnetization versus field patterns did not differ much with x composition. The ferromagnetic behaviour for 0.00 ≤ y ≤ 0.15 change to paramagnetic when y ³ 0.20. Resistivity versus temperature study showed that samples with y = 0.00 had metal-like behaviour. Nearly all samples with 0.00 < y < 0.20 showed metallic and semiconducting-like behaviour. LSBMT with y ³ 0.20 exhibited only semiconducting behaviour. The metal-insulator transition temperature, TP decreased with increment of x and/or y. At T < TP the resistivity curves can be fitted with the r = r0 + r2T2 relations. For T > Tp the curves can be fitted with the variable range hopping (VRH) model and small polaron hopping (SPH) model. The density of states at Fermi level, N(EF) values were between 1018 to 1022 eV-1cm-3. Polaron activation energy, Ep increased with y ranging from 47 meV to 210 meV. Magnetoresistance (MR) measurement showed an increment of the MR % when the magnetic field increased and temperature decreased. The maximum MR % was ~34 % for LSBMT with x = 0.00 and y = 0.15 at 100 K and 1.0 Tesla. Samples with y £ 0.10 showed low field magnetoresistance (LFMR) effect. At 1000 Hz LSBMT with x = 0.00, 0.25 and 0.75 exhibit a ferroelectric-paraelectric transition peak at 200 K, 250 K and 225 K respectively, with the highest e' value of 6.54 x 105 when x = 0.25, y = 0.20. The Nyquist plots of Z" versus Z' showed depressed semicircles contributed by the grain, grain boundary and/or electrode effect. Two relaxation processes occurred in the AC conductivity curve due to the grain and grain boundary. Materials with very high dielectric constant ~ 105 at 1000 kHz were successfully synthesized with x £ 0.75; y = 0.20 and all samples with y = 0.40. Samples with y = 0.40 have wide range of nearly frequency and temperature independent high dielectric constant. These samples are excellent for capacitors fabrication. Perovslate - Case studies 2009 Thesis http://psasir.upm.edu.my/id/eprint/7551/ http://psasir.upm.edu.my/id/eprint/7551/1/ABS_---__FS_2009_33.pdf application/pdf en public phd doctoral Universiti Putra Malaysia Perovslate - Case studies Faculty of Science English |
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Universiti Putra Malaysia |
| collection |
PSAS Institutional Repository |
| language |
English English |
| topic |
Perovslate - Case studies |
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Perovslate - Case studies Zainuddin, Zalita Microstructure, Magnetic and Electrical Properties of La0.67(Sr1-Xbax)0.33 Mn1-Ytiyo3 |
| description |
A study on the microstructure, magnetic and electrical properties of La0.67Sr0.33MnO3
substituted with Ba at Sr site and Ti at Mn site have been performed. Samples of
La0.67(Sr1-xBax)0.33 Mn1-yTiyO3 (LSBMT) with x = 0.00, 0.25, 0.50, 0.75 and 1.00;
and y = 0.00, 0.05, 0.10, 0.15, 0.20, 0.40 and 0.60 were prepared using solid state
reaction method. Quantitative compositional percentage data of the elements results
confirmed the expected La:Sr:Ba:Mn:Ti ratios for the prepared samples. X-ray
Diffractometer (XRD) spectrum showed single phase compounds, except for samples
with y = 0.60 which have La2Ti2O7 peaks. Sr substitution with Ba changed the
rhombohedral R-3c structure to cubic Pm3m, however Mn substitution with Ti only
increased the lattice parameters values, without changing the whole structure.
Scanning Electron Microscope (SEM) images showed a few porous structured
samples, with coarse and fine grains while the others showed large closely packed
grains with clear shapes and grain boundaries. The magnetization studies showed
that samples with y = 0.00 exhibited a transition from the ferromagnetic to the
paramagnetic phase as temperature increased and the Curie temperature, TC
decreased from 371 K to 341 K when x increased from 0.00 to 1.00. TC also decreased when y increased. Magnetization versus field patterns did not differ much
with x composition. The ferromagnetic behaviour for 0.00 ≤ y ≤ 0.15 change to
paramagnetic when y ³ 0.20. Resistivity versus temperature study showed that
samples with y = 0.00 had metal-like behaviour. Nearly all samples with 0.00 < y <
0.20 showed metallic and semiconducting-like behaviour. LSBMT with y ³ 0.20
exhibited only semiconducting behaviour. The metal-insulator transition temperature,
TP decreased with increment of x and/or y. At T < TP the resistivity curves can be
fitted with the r = r0 + r2T2 relations. For T > Tp the curves can be fitted with the
variable range hopping (VRH) model and small polaron hopping (SPH) model. The
density of states at Fermi level, N(EF) values were between 1018 to 1022 eV-1cm-3.
Polaron activation energy, Ep increased with y ranging from 47 meV to 210 meV.
Magnetoresistance (MR) measurement showed an increment of the MR % when the
magnetic field increased and temperature decreased. The maximum MR % was ~34
% for LSBMT with x = 0.00 and y = 0.15 at 100 K and 1.0 Tesla. Samples with y £
0.10 showed low field magnetoresistance (LFMR) effect. At 1000 Hz LSBMT with x
= 0.00, 0.25 and 0.75 exhibit a ferroelectric-paraelectric transition peak at 200 K, 250
K and 225 K respectively, with the highest e' value of 6.54 x 105 when x = 0.25, y =
0.20. The Nyquist plots of Z" versus Z' showed depressed semicircles contributed by
the grain, grain boundary and/or electrode effect. Two relaxation processes occurred
in the AC conductivity curve due to the grain and grain boundary. Materials with
very high dielectric constant ~ 105 at 1000 kHz were successfully synthesized with x
£ 0.75; y = 0.20 and all samples with y = 0.40. Samples with y = 0.40 have wide
range of nearly frequency and temperature independent high dielectric constant.
These samples are excellent for capacitors fabrication. |
| format |
Thesis |
| qualification_name |
Doctor of Philosophy (PhD.) |
| qualification_level |
Doctorate |
| author |
Zainuddin, Zalita |
| author_facet |
Zainuddin, Zalita |
| author_sort |
Zainuddin, Zalita |
| title |
Microstructure, Magnetic and Electrical Properties of
La0.67(Sr1-Xbax)0.33 Mn1-Ytiyo3 |
| title_short |
Microstructure, Magnetic and Electrical Properties of
La0.67(Sr1-Xbax)0.33 Mn1-Ytiyo3 |
| title_full |
Microstructure, Magnetic and Electrical Properties of
La0.67(Sr1-Xbax)0.33 Mn1-Ytiyo3 |
| title_fullStr |
Microstructure, Magnetic and Electrical Properties of
La0.67(Sr1-Xbax)0.33 Mn1-Ytiyo3 |
| title_full_unstemmed |
Microstructure, Magnetic and Electrical Properties of
La0.67(Sr1-Xbax)0.33 Mn1-Ytiyo3 |
| title_sort |
microstructure, magnetic and electrical properties of
la0.67(sr1-xbax)0.33 mn1-ytiyo3 |
| granting_institution |
Universiti Putra Malaysia |
| granting_department |
Faculty of Science |
| publishDate |
2009 |
| url |
http://psasir.upm.edu.my/id/eprint/7551/1/ABS_---__FS_2009_33.pdf |
| _version_ |
1747810699377115136 |