Motivation of research work
Recent research efforts have focused on its high density and even pure
BiFeO3 and research work has not enough achievement.
In the present work, we report on the effects of making glass and
crystalize BFO in glasses.
Purpose of a research talk
1.
To research about recent research efforts of Bismuth-Ferrite (BiFeO3 )
2.
To determine optimal parameters of being Bismuth-Ferrite
• To determine to depending on glass’s amorphous from Bi2O3 and
Fe2O3 components
• To determine critical temperature of annealing in BFO in silica glasses
Bismuth-Ferrite
Bismuth Ferrite (BiFeO3) is perhaps the only material that is both
magnetic and a strong ferroelectric at room temperature.
Bismuth ferrite (BiFeO3) is an inorganic chemical compound with
a perovskite structure. It is one of the most promising lead-free
piezoelectric materials by exhibiting multiferroic properties at room
temperature.
Multiferroic materials exhibit ferroelectric or antiferroelectric properties in
combination with ferromagnetic (or antiferromagnetic) properties in the
same phase.
Compositional phase diagram of
Bi2O3 and Fe2O3
Bismuth Ferrite is usually
prepared from equal parts of
Bi2O3 and Fe2O3.
Phase diagram of Bi2O3 and
Fe2O3 shows it.
Technology of extracting glass ceramic
BFO
Bi2O3
Fe2O3
SiO2
Mix powders
Melting at 11500С, 1 hour
Casting and glass formed
Annealing
Glass ceramic
BiFeO3
K2CO3
Bismuth Ferrite (BiFe03) Typical
Applications
1) Use in new high tech
magnetic tapes
2) Superconductivity
3) Environmental engineering
4) To enhance spontaneous
magnetization
Theoretical process?
Glass is metastable and will transform to the stable crystalline state if
enough thermal energy is available.
This transformation is called devitrification or crystallization, and
occurs by a two-step nucleation and crystal growth process. When the
temperature is increased high, crystal nuclei begin to form.
Crystallization makes glass opaque and does improve its other
properties such as strength and hardness.
Glass
Heat treatment/annealing/
Glass ceramic
Controlled or Uncontrolled crystallization?
Controlled crystallization
Criteria of controlled crystallization are:
High nucleation frequency, uniform
throughout the entire glass volume.
Very uniform crystal size
Very small crystallite
dimensions(usually only a few
micrometers)
Uncontrolled
crystallization
Uncontrolled crystallization is one
kind of defect.
Experimental procedure-I
(Melt a glass)
To prepare the BFO, molar percent of Bi2O3 and Fe2O3 should be equal. This
precursor was melted at 11500C by four versions: 25:25, 20:20, 15:15, 10:10.
Bi2O3 (mole %)
Fe2O3 (mole %)
Glass-J
25
25
Glass-G
20
20
Glass-I
15
15
Glass-H
10
10
Composition and raw materials calculation
(for glass J)
Raw
materials
g/mol
100g batch raw
materials
Bi2O3
465.93
60.6
Fe2O3
159.65
SiO2
60.07
K2CO3
138.18
M
[g/mol]
Mol %
Weight
in g
Weight
%
100g
batch
Bi2O3
465.93
25
116.48
60.6
60.6
Fe2O3
159.65
25
39.9
20.8
20.8
SiO2
60.07
33.33
20.02
10.42
10.42
K2O
94.19
16.67
15.7
8.2
8.2
20.8
10.4
12.054
XRD patterns of glasses
Fig. shows XRD patterns of glasses melted at 11500C by four versions: 25:25, 20:20, 15:15, 10:10 for 1 hour.
One of glasses was defect, it has uncontrolled crystallization(glass-J). Other 3 glasses were amorphous
Study of Atomic force microscope:
Bi2O3:Fe2O3=20:20
Glass-G’s surface nanostructure, AFM, it was not
uniform totally.
Appearance of Glass-G (20:20)
Study of Atomic force microscope:
Bi2O3:Fe2O3=15:15
Glass-I’s surface nanostructure, AFM, it was uniform
totally.
Appearance of Glass-I (15:15)
Study of Atomic force microscope:
Bi2O3:Fe2O3=10:10
Glass-H’s surface nanostructure, AFM, it wasn’t
uniform totally.
Appearance of Glass-H (10:10)
Experimental procedure-II
(Annealing of glasses)
After melting, we have annealed glasses by below condition. When we choose annealing
temperature 4000С and 5000С , based on pre research work.
Annealing condition, results
Glasses
Annealing
temperature, 0C
Annealing
time, h
Results
Glass-J,G,I,H
4000C
6
Crystallized
Glass-J,G,I,H
5000C
6
Crystallized
Annealing at 5000C
Fig. shows XRD patterns of BFO annealed at 5000C for 6 hours. The BFO was decomposed to
Bi2O3 and Fe2O3, it seems that temperature was high and not convenient to crystallize BFO.
Annealing at 4000C
(Bi2O3:Fe2O3=20:20)
Fig. shows XRD patterns of BFO annealed at 4000C for 6 hours. The BFO contained nonperovskite phase, such as Bi2Fe4O9, Bi2.88Fe5O12 , red is BiFeO3.
Annealing at 4000C
(Bi2O3:Fe2O3=15:15)
Fig. shows XRD patterns of BFO annealed at 4000C for 6 hours. The BFO contained nonperovskite phase, such as Bi2Fe4O9, Bi2.88Fe5O12 , red is BiFeO3.
Annealed samples
Bi2O3:Fe2O3=20:20
Bi2O3:Fe2O3=15:15
Conclusions
Glass-I was the most amorphous glass and glass-J was uncontrolled
crystallization.
All glasses crystallized at 4000C, annealing temperature 5000C was
inappropriate to glass ceramic BFO.
BFO started to form at 4000C and time was short, so should be
increase annealing time.
In recent work, we used Bi2O3 : Fe2O3 which were not high purity,
that’s why BFO contained non-perovskite phase.
References
Sven Bossuyt, California Institute of Technology Pasadena, California 2001
Peculiarities of a Solid-state synthesis of Multiferroic Polycrystalline BiFeO3, Matjaz
Valant, Anna-Karin Axelsson and Neil Alford, 2007
Materials Letter, 2008
Effects of Annealing Atmosphere on Crystallization and Electrical Properties in BiFeO3
thin films by chemical solution deposition. Kwi-Young YUN, Minoru Noda and
Masanori Okuyama, 2003
‘Microstructure of glass-ceramics and photosensitive glasses
’ Wiss. Ztschr.Friedrich-Schiller-University, Jena1979
Thanks for pay attention!