Summary of the invention
The present invention is directed to sol-gel method and prepare BiFeO
3problems existing and defect in film, provide a kind of BiFeO
3the preparation method of film, film obtained by this method does not have dephasign, and even structure is fine and close, and the rectangular degree of ferroelectric hysteresis loop is higher, and residual polarization is comparatively large, and ferroelectric properties is more excellent.
A kind of BiFeO of the present invention
3the feature of the preparation method of film is: raw material is Fe (NO
3)
39H
2o and Bi (NO
3)
35H
2o, mol ratio is 1:1.1, solvent is glacial acetic acid and ethylene glycol, volume ratio is 1:1, sequestrant is methyl ethyl diketone, the consumption of methyl ethyl diketone be itself and glacial acetic acid and ethylene glycol volume ratio be (1 ~ 4): 1:1, part is thanomin, the consumption of thanomin is the volume ratio of itself and glacial acetic acid is (0.01 ~ 0.04): 1, and the concentration of gained precursor solution is 0.2mol/L ~ 0.4 mol/L.
As a preferred embodiment of the present invention, the consumption of described methyl ethyl diketone be itself and glacial acetic acid and ethylene glycol volume ratio be 2:1:1, the consumption of described thanomin is the volume ratio of itself and glacial acetic acid is 0.01:1, and the concentration of described precursor solution is 0.3mol/L.
A kind of BiFeO of the present invention
3the preparation method of film, is characterized in that: comprise the following steps:
Step 1: the preparation of precursor solution: with Bismuth trinitrate Bi (NO
3)
35H
2o and iron nitrate Fe (NO
3)
39H
2o is raw material, and with ethylene glycol and glacial acetic acid for solvent, being sequestrant with methyl ethyl diketone, take thanomin as part, according to BiFeO
3stoichiometric ratio accurately takes Fe (NO
3)
39H
2o and Bi (NO
3)
35H
2o powder, wherein Bi (NO
3)
35H
2o need have suitably excessive, be dissolved in the mixed solution of glacial acetic acid and ethylene glycol after both are mixed, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, add appropriate part thanomin again, the pH value of regulator solution is between 1 ~ 2, mixed solution is at room temperature stirred 12 hours, the solution that final formation is certain density, even, transparent, stable, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: the pre-treatment of substrate: by ITO/glass substrate successively with each ultrasonic cleaning of acetone, dehydrated alcohol and deionized water 15 minutes to remove some organic pollutant and particle contamination, after having cleaned, the moisture on substrate is got rid of with sol evenning machine, then the hot plate being placed in 250 DEG C dries 180s, finally put into quick anneal oven pre-treatment 180 seconds under 450 DEG C of conditions, to remove the unrelieved stress existed in substrate material, the substrate handled well is placed in clean culture dish, notes keeping dry and cleaning;
Step 3: the preparation of film: precursor solution step 1 obtained utilizes sol evenning machine spin-coating to the substrate surface of step 2 gained, film terminates the rear hot plate being placed in 250 DEG C is fast dried, time is 60s, film after oven dry is put into quick anneal oven anneal, annealing process is first at 350 DEG C of pre-treatment 180s, 450 DEG C of insulation 60s, then at 550 DEG C of annealing 300s;
Step 4: repeating step 3 until obtain needed for film thickness after, obtained film is moved back 1200s 550 DEG C of ends in quick anneal oven.
In above-mentioned preparation method, for making up the volatilization of Bi under high temperature, Bi (NO
3)
35H
2o calculates by excessive 10mol%.
In above-mentioned preparation method, the even glue speed of sol evenning machine is 3000r/min, and spin coating time is 30s, and the film thickness after each even glue is 80nm.
BiFeO prepared by sol-gel method of the present invention
3film has the following advantages: precursor solution stable performance, and preparation technology is simple, and equipment cost is low, is beneficial to large-scale industrial production, is easy to the bismuth ferrite thin film preparing surperficial even compact, and does not have dephasign to generate in preparation process.
Embodiment
Embodiment 1
Step 1: according to BiFeO
3stoichiometric ratio accurately takes the Fe (NO that mol ratio is 1:1.1
3)
39H
2o and Bi (NO
3)
35H
2o powder, the glacial acetic acid that volume ratio is 1:1 is dissolved in after both being mixed, in the mixed solution of ethylene glycol, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, methyl ethyl diketone and glacial acetic acid, the volume ratio of ethylene glycol is 1:1:1, add part thanomin again, the volume ratio of thanomin and glacial acetic acid is 0.01:1, the pH value of regulator solution is 1, mixed solution is at room temperature stirred 12 hours, final formation is even, transparent, stable solution, strength of solution is 0.3 mol/L, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: ITO/glass substrate is cut into 2cm × 2cm specification, successively with each ultrasonic cleaning of acetone, dehydrated alcohol and deionized water 15 minutes to remove some organic pollutant and particle contamination, after having cleaned, the moisture on substrate is got rid of with sol evenning machine, then the hot plate being placed in 250 DEG C dries 180s, finally put into quick anneal oven at 450 DEG C of pre-treatment 180s, remove the unrelieved stress existed in substrate material, the substrate handled well is placed in clean culture dish, notes keeping dry;
Step 3: precursor solution step 2 obtained utilizes sol evenning machine spin-coating to the substrate surface of step 1 gained, even glue speed is 3000r/min, spin coating time is 30s, film terminates the rear hot plate being placed in 250 DEG C is fast dried, time is 60s, the film after oven dry is put into quick anneal oven and anneals, and annealing process is first at 350 DEG C of pre-treatment 180s, 450 DEG C of insulation 60s, then at 550 DEG C of annealing 300s;
Step 4: repeating step 3 until obtain needed for film thickness after, obtained film is moved back 1200s 550 DEG C of ends in quick anneal oven.
As Fig. 1, through x-ray diffractometer (German Brooker, D8) to the BiFeO obtained under the present embodiment condition
3film carries out structured testing, and the crystalline property prepared by discovery is good, and crystal phase structure is better, does not find dephasign.
Embodiment 2
Step 1: according to BiFeO
3stoichiometric ratio accurately takes the Fe (NO that mol ratio is 1:1.1
3)
39H
2o and Bi (NO
3)
35H
2o powder, the glacial acetic acid that volume ratio is 1:1 is dissolved in after both being mixed, in the mixed solution of ethylene glycol, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, methyl ethyl diketone and glacial acetic acid, the volume ratio of ethylene glycol is 2:1:1, add part thanomin again, the volume ratio of thanomin and glacial acetic acid is 0.01:1, the pH value of regulator solution is 1, mixed solution is at room temperature stirred 12 hours, final formation is even, transparent, stable solution, strength of solution is 0.3 mol/L, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: consistent with the step 2 in embodiment 1.
Step 3: consistent with the step 3 in embodiment 1.
Step 4: consistent with the step 4 in embodiment 1.
As Fig. 2, through x-ray diffractometer (German Brooker, D8) to the BiFeO obtained under the present embodiment condition
3film carries out structured testing, and the crystalline property prepared by discovery is good, and crystal phase structure is good, does not find dephasign.Utilize ferroelectric test macro (Precision Pro. Radiant Technologies) to gained BiFeO
3the ferroelectric hysteresis loop of film characterizes, and as shown in Figure 3, find that the rectangular degree of ferroelectric hysteresis loop is higher, residual polarization (2Pr) can reach 74 μ C/cm
2.Fig. 4 is for utilizing scanning electron microscope to gained BiFeO
3the sign of the film surface appearance that film carries out, the film surface flat smooth as can be seen from the figure prepared, does not observe tiny crack and pore, and the membrane structure even compact of preparation is described, grain size is more even.Above test result shows, prepared BiFeO
3film has excellent crystalline structure and surface topography, and ferroelectric properties is better.
Embodiment 3
Step 1: according to BiFeO
3stoichiometric ratio accurately takes the Fe (NO that mol ratio is 1:1.1
3)
39H
2o and Bi (NO
3)
35H
2o powder, the glacial acetic acid that volume ratio is 1:1 is dissolved in after both being mixed, in the mixed solution of ethylene glycol, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, methyl ethyl diketone and glacial acetic acid, the volume ratio of ethylene glycol is 3:1:1, add part thanomin again, the volume ratio of thanomin and glacial acetic acid is 0.01:1, the pH value of regulator solution is 1, mixed solution is at room temperature stirred 12 hours, final formation is even, transparent, stable solution, strength of solution is 0.3 mol/L, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: consistent with the step 2 in embodiment 1.
Step 3: consistent with the step 3 in embodiment 1.
Step 4: consistent with the step 4 in embodiment 1.
As can be seen from Figure 5, gained BiFeO
3film crystal structure is good, and does not occur dephasign in film.
Embodiment 4
Step 1: according to BiFeO
3stoichiometric ratio accurately takes the Fe (NO that mol ratio is 1:1.1
3)
39H
2o and Bi (NO
3)
35H
2o powder, the glacial acetic acid that volume ratio is 1:1 is dissolved in after both being mixed, in the mixed solution of ethylene glycol, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, methyl ethyl diketone and glacial acetic acid, the volume ratio of ethylene glycol is 4:1:1, add part thanomin again, the volume ratio of thanomin and glacial acetic acid is 0.01:1, the pH value of regulator solution is 1, mixed solution is at room temperature stirred 12 hours, final formation is even, transparent, stable solution, strength of solution is 0.3 mol/L, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: consistent with the step 2 in embodiment 1.
Step 3: consistent with the step 3 in embodiment 1.
Step 4: consistent with the step 4 in embodiment 1.
As can be seen from Figure 6, gained BiFeO
3film crystal structure is good, and does not occur dephasign in film.
Embodiment 5
Step 1: according to BiFeO
3stoichiometric ratio accurately takes the Fe (NO that mol ratio is 1:1.1
3)
39H
2o and Bi (NO
3)
35H
2o powder, the glacial acetic acid that volume ratio is 1:1 is dissolved in after both being mixed, in the mixed solution of ethylene glycol, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, methyl ethyl diketone and glacial acetic acid, the volume ratio of ethylene glycol is 2:1:1, add part thanomin again, the volume ratio of thanomin and glacial acetic acid is 0.01:1, the pH value of regulator solution is 1, mixed solution is at room temperature stirred 12 hours, final formation is even, transparent, stable solution, strength of solution is 0.2 mol/L, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: consistent with the step 2 in embodiment 1.
Step 3: consistent with the step 3 in embodiment 1.
Step 4: consistent with the step 4 in embodiment 1.
As can be seen from Figure 7, gained BiFeO
3film crystal structure is good, and does not occur dephasign in film.
Embodiment 6
Step 1: according to BiFeO
3stoichiometric ratio accurately takes the Fe (NO that mol ratio is 1:1.1
3)
39H
2o and Bi (NO
3)
35H
2o powder, the glacial acetic acid that volume ratio is 1:1 is dissolved in after both being mixed, in the mixed solution of ethylene glycol, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, methyl ethyl diketone and glacial acetic acid, the volume ratio of ethylene glycol is 2:1:1, add part thanomin again, the volume ratio of thanomin and glacial acetic acid is 0.01:1, the pH value of regulator solution is 1, mixed solution is at room temperature stirred 12 hours, final formation is even, transparent, stable solution, strength of solution is 0.4 mol/L, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: consistent with the step 2 in embodiment 1.
Step 3: consistent with the step 3 in embodiment 1.
Step 4: consistent with the step 4 in embodiment 1.
As can be seen from Figure 8, gained BiFeO
3film crystal structure is good, and does not occur dephasign in film.
Embodiment 7
Step 1: according to BiFeO
3stoichiometric ratio accurately takes the Fe (NO that mol ratio is 1:1.1
3)
39H
2o and Bi (NO
3)
35H
2o powder, the glacial acetic acid that volume ratio is 1:1 is dissolved in after both being mixed, in the mixed solution of ethylene glycol, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, methyl ethyl diketone and glacial acetic acid, the volume ratio of ethylene glycol is 2:1:1, add part thanomin again, the volume ratio of thanomin and glacial acetic acid is 0.025:1, the pH value of regulator solution is 1.5, mixed solution is at room temperature stirred 12 hours, final formation is even, transparent, stable solution, strength of solution is 0.3 mol/L, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: consistent with the step 2 in embodiment 1.
Step 3: consistent with the step 3 in embodiment 1.
Step 4: consistent with the step 4 in embodiment 1.
As can be seen from Figure 9, gained BiFeO
3film crystal structure is good, and does not occur dephasign in film.
Embodiment 8
Step 1: according to BiFeO
3stoichiometric ratio accurately takes the Fe (NO that mol ratio is 1:1.1
3)
39H
2o and Bi (NO
3)
35H
2o powder, the glacial acetic acid that volume ratio is 1:1 is dissolved in after both being mixed, in the mixed solution of ethylene glycol, at room temperature dissolve completely up to powder with magnetic stirrer 8 is little, then sequestrant methyl ethyl diketone is added in the solution, methyl ethyl diketone and glacial acetic acid, the volume ratio of ethylene glycol is 2:1:1, add part thanomin again, the volume ratio of thanomin and glacial acetic acid is 0.04:1, the pH value of regulator solution is 2, mixed solution is at room temperature stirred 12 hours, final formation is even, transparent, stable solution, strength of solution is 0.3 mol/L, by gained solution at 25 DEG C aging 24 hours, obtain required precursor solution.
Step 2: consistent with the step 2 in embodiment 1.
Step 3: consistent with the step 3 in embodiment 1.
Step 4: consistent with the step 4 in embodiment 1.
As can be seen from Figure 10, gained BiFeO
3film crystal structure is good, and does not occur dephasign in film.
The foregoing is only one embodiment of the present invention, it not whole or unique embodiment, the conversion of those of ordinary skill in the art by reading specification sheets of the present invention to any equivalence that technical solution of the present invention is taked, is claim of the present invention and contains.