Motivation of research work

Recent research efforts have focused on its high density and even pure BiFeO 3 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 (BiFeO 3 ) 2.

To determine optimal parameters of being Bismuth-Ferrite • To determine to depending on glass’s amorphous from Bi 2 O 3 Fe 2 O 3 components and • To determine critical temperature of annealing in BFO in silica glasses

Bismuth-Ferrite

Bismuth Ferrite (BiFeO 3 ) is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature.

Bismuth ferrite (BiFeO 3 ) 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 Bi 2 O 3 and Fe 2 O 3

Bismuth Ferrite is usually prepared from equal parts of Bi 2 O 3 and Fe 2 O 3 .

Phase diagram of Bi 2 O 3 Fe 2 O 3 shows it.

and

Technology of extracting glass ceramic BFO

Bi 2 O 3 Fe 2 O 3 SiO 2 K 2 CO 3 Mix powders Melting at 1150 0 С, 1 hour Casting and glass formed Annealing Glass ceramic BiFeO 3

Bismuth Ferrite (BiFe0 3 ) 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 Bi 2 O 3 and Fe 2 O 3 should be equal. This precursor was melted at 1150 0 C by four versions: 25:25, 20:20, 15:15, 10:10.

Glass-J Glass-G Glass-I Glass-H Bi 2 O 3 (mole %)

25 20 15 10

Fe 2 O 3 (mole %)

25 20 15 10

Composition and raw materials calculation (for glass J)

Raw materials Bi 2 O 3 g/mol

465.93

Fe 2 O SiO 2 3

159.65

60.07

K 2 CO 3

138.18

100g batch raw materials

60.6

20.8

10.4

12.054

Bi 2 O 3 Fe 2 O 3 SiO 2 K 2 O M [g/mol] Mol % Weight in g Weight % 100g batch

465.93

159.65

60.07

94.19

25 25 33.33

16.67

116.48

39.9

20.02

15.7

60.6

20.8

10.42

8.2

60.6

20.8

10.42

8.2

XRD patterns of glasses

Fig. shows XRD patterns of glasses melted at 1150 0 C 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: Bi 2 O 3 :Fe 2 O 3 =20:20

Glass-G’s surface nanostructure, AFM, it was not uniform totally.

Appearance of Glass-G (20:20)

Study of Atomic force microscope: Bi 2 O 3 :Fe 2 O 3 =15:15

Glass-I’s surface nanostructure, AFM, it was uniform totally.

Appearance of Glass-I (15:15)

Study of Atomic force microscope: Bi 2 O 3 :Fe 2 O 3 =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 400 0 С and 500 0 С , based on pre research work.

Annealing condition, results

Glasses Annealing temperature, 0 C Annealing time, h Results Glass-J,G,I,H Glass-J,G,I,H 400 0 C 500 0 C 6 6 Crystallized Crystallized

Annealing at 500 0 C

Fig. shows XRD patterns of BFO annealed at 500 0 C for 6 hours. The BFO was decomposed to Bi 2 O 3 and Fe 2 O 3 , it seems that temperature was high and not convenient to crystallize BFO.

Annealing at 400 0 C (Bi 2 O 3 :Fe 2 O 3 =20:20)

Fig. shows XRD patterns of BFO annealed at 400 0 C for 6 hours. The BFO contained non perovskite phase, such as Bi 2 Fe 4 O 9 , Bi 2.88

Fe 5 O 12 ,

red is BiFeO 3

.

Annealing at 400 0 C (Bi 2 O 3 :Fe 2 O 3 =15:15)

Fig. shows XRD patterns of BFO annealed at 400 0 C for 6 hours. The BFO contained non perovskite phase, such as Bi 2 Fe 4 O 9 , Bi 2.88

Fe 5 O 12 ,

red is BiFeO 3

.

Annealed samples

Bi 2 O 3 :Fe 2 O 3 =20:20 Bi 2 O 3 :Fe 2 O 3 =15:15

Conclusions

Glass-I was the most amorphous glass and glass-J was uncontrolled crystallization. All glasses crystallized at 400 0 C, annealing temperature 500 0 C was inappropriate to glass ceramic BFO. BFO started to form at 400 0 C and time was short, so should be increase annealing time.

In recent work, we used Bi 2 O 3 : Fe 2 O 3 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 BiFeO 3 , Matjaz Valant, Anna-Karin Axelsson and Neil Alford, 2007 Materials Letter, 2008 Effects of Annealing Atmosphere on Crystallization and Electrical Properties in BiFeO 3 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

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