1. THE PREPARATION OF BiFeO3 TACTILE SENSOR
Date : 2017/05/28
THE PREPARATION OF BiFeO3 TACTILE SENSOR
Reporter : Jia Yun Kuo

2. Outline 1 2 3 4 5 Introduction Experiment Results & Discussion
Conclusions
Reference 1 2 3 4 5

3. Introduction
The piezoelectricity was discovered in 1880 by Pierre Curie and Jacques Curie. They found the electrical potential difference when the mechanical stress was applied on the quartz and this voltage was proportional to the stress. [1]

4. Piezoelectricity
The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry .
Schematic of direct piezoelectric effect; (a) piezoelectric material, (b) energy generation under tension, (c) energy generation under compression
Figure 1. Schematic of direct piezoelectric effect.[2]

5. Piezoelectric film
The piezoelectric film is a kind of force feedback materials, but the traditional type is leaded and ceramic.
Therefore, the purpose of this research is to develop a lead-free and flexible piezoelectric film for an effective response detection of tactile devices.

6. Piezoelectricity applications
Currently, industrial manufacturing is the largest applied market for piezoelectric devices, especially the automotive industry.
Furthermore, amount of demands also come from medical instruments as well as surgical instruments.

7. BiFeO3
BiFeO3, one of the most promising multiferroic materials, is well studied in literature.
There are numerous methods for deposition of BiFeO3 thin film such as sol-gel process, spray pyrolysis, pulse laser deposition, photo chemical deposition, molecular beam epitaxy, chemical vapor deposition and sputtering, etc.

8. Measurement

9. SEM
The SEM mode is detection of secondary electrons emitted by atoms excited by the electron beam.
The electron beam is generally scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image.
Figure 2. Scanning Electron Microscope.

10. XRD
X-ray crystallography is a technique used for determining the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of incident X-rays to diffract into many specific directions.
Figure 3. Scanning Electron Microscope.

11. Fabrication

12. Flow chart of fabrication
Sol-gel preparation
High temperature furnace at 500℃ for 20 mins
Atmospheric plasma
Crystallization by XRD,SEM No
Spin coating 450rpm for 10s, then 3000rpm 30s
Enough layers
Yes
Insufficient layers
Force-feedback voltage testing
Heating at 250℃ for 3mins
This is my Flow chart of fabrication.
These are about BiFeO3 film how to prepare.
I will describe in detail on the next page.
If the film can’t observe the crystal by SEM and XRD.
We will return to prepare the thin film.
If the film can observe the crystal by SEM and XRD.
We will do Force-feedback voltage testing and scaling.
Force-feedback voltage scaling
High temperature furnace at 350℃ for 10 mins

13. Solution parameters Fe(NO3)3∙9H2O 0.3 mol Bi(NO3)3∙5H2O 0.33 mol
Acetic acid
15 ml
Ethylene glycol
Acetyl acetone
30 ml
BiFeO3 solution
0.3 mol/L
This table can see need how many chemicals to prepare BiFeO3 solution.  
Iron nitrate nonahydrate and Bismuth nitrate, pentahydrate mole ratio is one to one point one.
Acetic acid, ethylene glycol and acetyl acetone volume ratio is one to one to two.
Final BiFeO3 solution will be zero point three molarity.
Table 1. The parameters of BiFeO3 solution.[3]

14. Process parameters Temperature Time Spin coating Room temperature
450 rpm 10s
3000 rpm 30s
Heating
250 ℃
3 mins
High temperature furnace
350 ℃
10 mins
Final high temperature furnace
500 ℃
20 mins
This table can see the process steps need how much time and temperature.
Spin coating at Room temperature.
First use slow speed 450 rpm (Revolution per Minute) for 10s then fast 3000rpm (Revolution per Minute) for 30s.
Heating at 250℃ for 3 mins.
High temperature furnace at 350℃ for 10 mins.
Final High temperature furnace at 500℃ for 20 mins.
Table 2. The parameters of BiFeO3 process.

15. Solution preparation by sol-gel method
Fe(NO3)3∙9H2O Bi(NO3)3∙5H2O
Powder preparation
Acetic acid
Ethylene glycol
First, Iron nitrate nonahydrate and Bismuth nitrate pentahydrate powder preparation then add in Acetic acid and ethylene glycol stirring for 8 hours.
After 8 hours, add in acetyl acetone and ethanolamine stirring for 12 hours.
Finally, solution deposition of 24 hours.
And then can be prepared thin film.
Deposition for 24hrs
Acetylacetone
Ethanolamine
Stirring for 12hrs
Stirring for 8hrs

16. Thin film production Atmospheric plasma
Spin coating 450 rpm for 10s, then 3000 rpm 30s
At 250 ℃ for 3 mins
First step, clean substrate by atmospheric plasma.
Second step, the sol-gel need coated 450 rpm (Revolution per Minute) for 10s then 3000rpm (Revolution per Minute) for 30s by spin coating then heating at 250 degree for 3mins.
Next step put in high temperature furnace at 350 degree for 10 mins.
Repeat second to forth step until need layers.
Finally, put in high temperature furnace at 500 degree for 20 mins.
High temperature furnace at 500 ℃ for 20 mins
High temperature furnace at 350 ℃ for 10 mins

17. Schematic Diagram
This is schematic diagram of tactile sensor based on BiFeO3 thin film.
We use polyimide substrate and is a square 10mm on a side.
Then deposition BiFeO3 sol-gel form thin film.
Figure 4. The schematic diagram of tactile sensor based on BiFeO3 thin film.

18. Products
These two figures are BiFeO3 thin film. This is 0.3 mol% of 3 layers at 500 degrees. Another is 0.3 mol% of 3 layers at 400 degrees.
Figure 5. BiFeO3 thin film of 0.3 mol% of 3 layers at 500℃.
Figure 6. BiFeO3 thin film of 0.3 mol% of 3 layers at 400℃.

19. Results & Discussion

20. The crystallization of BiFeO3
This figure x axis is incident angle of incident light and y axis is arbitrary unit strength.
The first peak is BiFeO3 lattice growth direction (101).
The second peak is other phase of Bismuth ferrite, because pure phase synthesis was difficult.
The peak of annealing temperature at 400 degrees and 500 degrees more than other strength.
Figure 11. The XRD of BiFeO3 thin film with 0.3 mol% and different annealing temperature.

21. The SEM photograph to compare different annealing temperature with concentration in 0.3 mol%(1/2)
The annealing temperature at 350℃ and 400℃.
We can see the thin film have small particles, but it Very few.
Figure 7. BiFeO3 thin film at 350 ℃.
Figure 8. BiFeO3 thin film at 400 ℃.

22. The SEM photograph to compare different annealing temperature with concentration in 0.3 mol%(2/2)
The annealing temperature at 450℃, also have few small particles.
These thin film only have few particle, because these temperatures cannot crystallize.
But the annealing temperature at 500℃.
We can see the thin film has many particles, and it is distributed.
So, we choose the temperature at 500 degrees to do experiment.
Because, the sem figure not good at 400 degrees, therefore we didn’t use this annealing temperature.
Figure 9. BiFeO3 thin film at 450 ℃.
Figure 10. BiFeO3 thin film at 500 ℃.

23. Experimental results for different annealing temperatures
Figure 12. BiFeO3 thin film with 0.3 mol% of 3 layers and different annealing temperature.
We can see the 500 degree more than other annealing temperature better.
Although, more than 500 degrees will be better, but limit material cannot bear higher temperature.
Figure 12. BiFeO3 thin film with 0.3 mol% of 3 layers and different annealing temperature.

24. Experimental results for different layers with 1.5N
Figure 13. BiFeO3 thin film with 0.15 mol%, 0.3 mol% and annealing temperature at 500℃.
We use force is 1.5 NewtonWe can see 3 layers with 0.3 mol% is better.This voltage is 41 mv.But, the molarity in 0.15 mol% more than 6 layers maybe will be better.So, we will do more layers experiments to compare.
Figure 13. BiFeO3 thin film with mol% ,0.3 mol% and annealing temperature at 500℃.

25. Conclusions
BiFeO3 particles are homogeneously dispersed as the annealing temperature is at 500℃. In addition, it will build a better force feedback film.
Based on the force-feedback analysis, a higher voltage could be attained for the multilayer coatings, which might be related to the crystal structure.[4]

26. References
[1]P. Curie, J. Curie,” Développement par compression de l’électricité polaire dans les cristaux hémièdres à faces inclinées”, Comptes rendus de l'Académie des sciences, 01, , 1880.
[2] perspective/alternative-resources-for-renewable-energy-piezoelectric-and- photovoltaic-smart-structures
[3]T.Y. Lei, Y.Y. Sun, H. Ren, Y. Zhang, W. Cai, C.L. Fu,” Research Progress in the Sol-Gel Preparation and Electrical Properties of Bismuth Ferrite Thin Films”, Surface technology, 43, , 2014.
[4]S.W. Yu, J.Y. Cai, Y.F. Yan, J.R. Cheng,” BiFeO3 Thin Films Fabricated by Sol-gel Method and Its Thickness Dependence”, Journal of shanghai university (natural science edition), 14, 509–513, 2008. 19

27. Thank you for your attention