CN112062552A - A kind of preparation method of lead-free thin film material using phase transition induction - Google Patents

Abstract

The invention relates to a preparation method of lead-free thin film material induced by phase transition, and belongs to the technical field of chemical engineering. A method for preparing a lead-free thin film material utilizing phase transition induction, firstly preparing a BCT-BMT precursor solution, and spin-coating the obtained BCT-BMT precursor solution on a Pt(111)/TiO _x /SiO ₂ /Si(100) substrate , to obtain a wet film; the obtained wet film is dried, pyrolyzed, and annealed to obtain a layer of BCT-BMT thin film; the above steps are repeated to prepare a multi-layer BCT-BMT thin film. The preparation method of the invention is relatively simple, and is a convenient and quick preparation technology.

Description

A kind of preparation method of lead-free thin film material using phase transition induction

technical field

The invention relates to a preparation method of lead-free thin film material induced by phase transition, and belongs to the technical field of chemical engineering.

Background technique

Ferroelectric/antiferroelectric thin-film or thick-film materials with large positive/negative electric card effects play a crucial role in the design of commercial chip-scale refrigeration devices. In recent years, breakthroughs in the large positive card effect in ferroelectric thin films have been reported frequently in many composition systems, generally in lead-based ferroelectric or antiferroelectric thin film materials represented by lead zirconate titanate (PZT). For the positive electric card effect, the change of the electric card refrigeration temperature or entropy generally increases with the increase of the electric field. In contrast, the negative electric card effect reported so far is generally obtained under a moderate electric field. When the electric field exceeds a certain electric field, the absolute value of the electric card refrigeration temperature change will decrease with the increase of the electric field, thus limiting and causing Its total absolute value is low, far smaller than the positive electric card effect value reported so far.

Over the past decade, the electric card effect has been extensively studied due to its potential application in commercial solid-state refrigeration units. Since 2006, it has been observed that the positive galvanic effect of lead-based materials increases significantly from 12K to 40K, but the negative galvanic effect still remains at a very low level around 10K, which limits further improvements in cooling efficiency, especially when we try to operate in a When combining negative and positive electrical card effects during a cooling cycle. Due to the toxicity of lead, people are always looking for lead-free materials to replace lead-containing materials.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of lead-free thin film material using phase transition induction. BCT-BMT is a ferroelectric material with a huge electric card effect, which was prepared on a Pt(111)/TiO _x /SiO ₂ /Si(100) (0<x<10) substrate by a sol-gel synthesis method. The BCT-BMT lead-free relaxor ferroelectric thin film material has a huge negative electric card effect. Using this huge negative electric card effect combined with the positive electric card effect will make the ferroelectric thin film material in chip-level electronic components (such as CPU, etc.). ) and other solid-state refrigeration technologies have greatly improved the refrigeration efficiency, and the direction of the electric field applied in a single refrigeration cycle does not need to be changed alternately; alternating electric field. The breakthrough of this research achievement will provide a new technical path for the design and preparation of solid-state electric card refrigeration devices, and is expected to solve the problem of performance degradation and deterioration of electronic components due to their heating problems.

The object of the present invention is achieved through the following technical solutions:

A method for preparing a lead-free thin film material utilizing phase transition induction, comprising the following steps:

1) Prepare a BCT-BMT precursor solution, the general formula of the BCT-BMT is n(Ba _x Ca _(1-x) )TiO ₃ -(1-n)Bi(Mg _y Ti _(1-y) )O ₃ , where 0<x<1, 0<y<1, 0<n<1;

2) spin-coating the BCT-BMT precursor solution obtained in step 1) on the Pt(111)/TiO _x /SiO ₂ /Si(100) substrate to obtain a wet film;

3) drying, pyrolyzing and annealing the wet film obtained in step 2) to obtain a layer of BCT-BMT film, the annealing temperature is 700-800° C., the annealing time is 20-30 min, and the annealing environment is an air atmosphere;

4) Repeat steps 2) and 3) to prepare multilayer BCT-BMT films.

Preferably, the BCT-BMT precursor solution in step 1) is prepared by the following method: mixing Bi(CH ₃ COO) ₃ , Ca(CH ₃ COO) ₂ and Ba(CH ₃ COO) ₂ at 60-100 ℃ dissolved in a mixed liquid of glacial acetic acid and deionized water, while Mg(OC ₂ H ₅ ) ₂ , Ti(OCH(CH ₃ ) ₂ ) ₄ were dissolved in CH ₃ OCH ₂ -CH ₂ OH and CH ₃ COCH ₂ In the mixed liquid of COCH ₃ , the two obtained mixed liquids were stirred and mixed again at room temperature for 30 min, and left for 20-30 h to obtain a BCT-BMT precursor solution with a concentration of 0.2-0.3 M.

Preferably, the rotational speed of the spin coating in step 2) is 4000-6000 rpm, and the spin coating time is 30-40 s.

Preferably, in step 3), the drying temperature is 100-300°C, and the drying time is 3-10min; the pyrolysis temperature is 350-500°C, and the pyrolysis time is 3-10min.

Preferably, 8 layers of BCT-BMT films are obtained in step 4).

The beneficial effects of the invention are as follows: obtaining a film with the advantages of high purity, good compactness, small average grain size, high electric field breakdown strength, large electric card effect and the like; the preparation method of the invention is relatively simple, and is a convenient and fast preparation technology.

Description of drawings

Fig. 1 is the electric card performance map of BCT-BMT film under different electric field intensities obtained in Example 1 of the present invention;

Figure 2 is a schematic diagram of the mechanism of phase transition induction in the present invention.

Detailed ways

The present invention will be described in further detail below with reference to specific examples, but the embodiments of the present invention are not limited to the scope represented by the examples. These examples are only used to illustrate the present invention, but not to limit the scope of the present invention. In addition, after reading the content of the present invention, those skilled in the art can make various modifications to the present invention, and these equivalent changes also fall within the scope defined by the appended claims of the present invention.

Example 1

A method to achieve a giant negative charge card effect using phase transition-induced lead-free thin film materials, specifically n(Ba _x Ca _(1-x) )TiO ₃ –(1-n)Bi(Mg _y Ti _(1-y) ) O ₃ (BCT-BMT) ferroelectric thin film, where x=0.8, y=0.5, n=0.5, i.e. 0.5(Ba _0.8 Ca _0.2 )TiO ₃ -0.5Bi(Mg _0.5 Ti _0.5 )O ₃ ferroelectric thin film, which The preparation method includes the following specific steps:

(1) According to the molar ratio (1.05×0.5):(0.5×0.2):(0.5×0.8):(1.05×0.5×0.5):(0.5+0.5×0.5), respectively weigh the Bi(CH) of 5% excess Bi Preparation of BCT-BMT Precursors by 3COO) ₃ , Ca(CH ₃ COO) ₂ , Ba(CH ₃ COO) ₂ , Mg(OC ₂ H ₅ ) ₂ and Ti(OCH(CH ₃ ) ₂ ) ₄ in ₅ % excess Mg body solution;

Bi(CH ₃ COO) ₃ , Ca(CH ₃ COO) ₂ and Ba(CH ₃ COO) ₂ containing excess Bi were dissolved in a mixed liquid of glacial acetic acid and deionized water at 60°C, while the excess Mg containing Mg(OC ₂ H ₅ ) ₂ , Ti(OCH(CH ₃ ) ₂ ) ₄ were dissolved in the mixed liquid of CH ₃ OCH ₂ -CH ₂ OH and CH ₃ COCH ₂ COCH ₃ , and finally the first two mixed liquids were mixed again Stir at room temperature for 30 min, and place for 20 h to obtain a BCT-BMT precursor solution with a concentration of 0.2 M;

(2) The BCT-BMT precursor solution obtained in step (1) was spin-coated on the Pt(111)/TiO ₂ /SiO ₂ /Si(100) substrate at a speed of 4000 rpm for 30 s using a glue spinner to obtain a wet film ;

(3) The wet film obtained in step (2) was first dried at 100° C. for 3 minutes, then pyrolyzed at 350° C. for 3 minutes, and finally annealed at 700° C. in an air atmosphere for 20 minutes. A layer of BCT-BMT film was obtained;

(4) Repeating step (2) and step (3) 8 times to obtain an 8-layer BCT-BMT film.

Example 2

A method to achieve a giant negative charge card effect using phase transition-induced lead-free thin film materials, specifically n(Ba _x Ca _(1-x) )TiO ₃ –(1-n)Bi(Mg _y Ti _(1-y) ) O ₃ (BCT-BMT) ferroelectric thin film, where x=0.5, y=0.8, n=0.5, i.e. 0.5(Ba _0.5 Ca _0.5 )TiO ₃ -0.5Bi(Mg _0.8 Ti _0.2 )O ₃ ferroelectric thin film, which The preparation method includes the following specific steps:

(1) According to the molar ratio (1.05×0.5):(0.5×0.5):(0.5×0.5):(1.05×0.5×0.8):(0.5+0.5×0.2), respectively weigh the Bi(CH) of 5% excess Bi Preparation of BCT-BMT Precursors by 3COO) ₃ , Ca(CH ₃ COO) ₂ , Ba(CH ₃ COO) ₂ , Mg(OC ₂ H ₅ ) ₂ and Ti(OCH(CH ₃ ) ₂ ) ₄ in ₅ % excess Mg body solution;

Dissolve excess Bi(CH ₃ COO) ₃ , Ca(CH ₃ COO) ₂ and Ba(CH ₃ COO) ₂ in a mixed liquid of glacial acetic acid and deionized water at 80°C, while Mg(CH 3 COO) containing excess Mg( OC ₂ H ₅ ) ₂ and Ti(OCH(CH ₃ ) ₂ ) ₄ were dissolved in the mixed liquid of CH ₃ OCH ₂ -CH ₂ OH and CH ₃ COCH ₂ COCH ₃ , and finally the first two mixed liquids were mixed again at room temperature Under stirring for 30min, and placed for 25h to obtain a BCT-BMT precursor solution with a concentration of 0.23M;

(2) The BCT-BMT precursor solution obtained in step (1) was spin-coated on the Pt(111)/TiO ₂ /SiO ₂ /Si(100) substrate at a speed of 4500 rpm for 33 s using a glue spinner to obtain a wet film ;

(3) The wet film obtained in step (2) was first dried at 110° C. for 5 minutes, then pyrolyzed at 450° C. for 7 minutes, and finally annealed at 750° C. in an air atmosphere for 22 minutes. A layer of BCT-BMT film was obtained;

(4) Repeating step (2) and step (3) 8 times to obtain an 8-layer BCT-BMT film.

Example 3

A method to achieve a giant negative charge card effect using phase transition-induced lead-free thin film materials, specifically n(Ba _x Ca _(1-x) )TiO ₃ –(1-n)Bi(Mg _y Ti _(1-y) ) O ₃ (BCT-BMT) ferroelectric thin film, where x=0.5, y=0.8, n=0.5, i.e. 0.5(Ba _0.5 Ca _0.5 )TiO ₃ -0.5Bi(Mg _0.8 Ti _0.2 )O ₃ ferroelectric thin film, which The preparation method includes the following specific steps:

(1) According to the molar ratio (1.05×0.5):(0.5×0.5):(0.5×0.5):(1.05×0.5×0.8):(0.5+0.5×0.2), respectively weigh the Bi(CH) of 5% excess Bi Preparation of BCT-BMT Precursors by 3COO) ₃ , Ca(CH ₃ COO) ₂ , Ba(CH ₃ COO) ₂ , Mg(OC ₂ H ₅ ) ₂ and Ti(OCH(CH ₃ ) ₂ ) ₄ in ₅ % excess Mg body solution;

Bi(CH ₃ COO) ₃ , Ca(CH ₃ COO) ₂ and Ba(CH ₃ COO) ₂ containing excess Bi were dissolved in a mixed liquid of glacial acetic acid and deionized water at 100 °C, while the excess Mg containing Mg(OC ₂ H ₅ ) ₂ , Ti(OCH(CH ₃ ) ₂ ) ₄ were dissolved in the mixed liquid of CH ₃ OCH ₂ -CH ₂ OH and CH ₃ COCH ₂ COCH ₃ , and finally the first two mixed liquids were mixed again Stir at room temperature for 30 min and stand for 30 h to obtain a BCT-BMT precursor solution with a concentration of 0.3 M;

(2) The BCT-BMT precursor solution obtained in step (1) was spin-coated on the Pt(111)/TiO ₂ /SiO ₂ /Si(100) substrate at a speed of 6000 rpm for 40 s using a glue spinner to obtain a wet film ;

(3) The wet film obtained in step (2) was first dried at 300° C. for 10 minutes, then pyrolyzed at 500° C. for 10 minutes, and finally annealed at 800° C. in an air atmosphere for 30 minutes. A layer of BCT-BMT film was obtained;

(4) Repeating step (2) and step (3) 8 times to obtain an 8-layer BCT-BMT film.

Claims (5)

1. A method for preparing a lead-free film material by utilizing phase change induction is characterized by comprising the following steps:

1) preparing a precursor solution of BCT-BMT having the general formula n (Ba)_xCa_(1-x))TiO₃-(1-n)Bi(Mg_yTi_(1-y))O₃Wherein x is more than 0 and less than 1, y is more than 0 and less than 1, and n is more than 0 and less than 1;

2) spin coating the BCT-BMT precursor solution obtained in the step 1) on Pt (111)/TiO_x/SiO₂a/Si (100) substrate to obtain a wet film;

3) drying, pyrolyzing and annealing the wet film obtained in the step 2) to obtain a layer of BCT-BMT film, wherein the annealing temperature is 700-800 ℃, the annealing time is 20-30min, and the annealing environment is air atmosphere;

4) and (3) repeating the step 2) and the step 3) to obtain the multilayer BCT-BMT film.

2. The method for preparing a lead-free thin film material using phase transition induction according to claim 1, wherein the BCT-BMT precursor solution of step 1) is prepared by: adding Bi (CH)₃COO)₃、Ca(CH₃COO)₂And Ba (CH)₃COO)₂Dissolving in mixed liquid of glacial acetic acid and deionized water at 60-100 deg.C while adding Mg (OC)₂H₅)₂、Ti(OCH(CH₃)₂)₄Is dissolved in CH₃OCH₂-CH₂OH and CH₃COCH₂COCH₃And stirring the two mixed solutions at room temperature for 30min, standing for 20-30h to obtain BCT-BMT precursor solution with the concentration of 0.2-0.3M.

3. The method as claimed in claim 1, wherein the spin-coating speed in step 2) is 4000-6000rpm, and the spin-coating time is 30-40 s.

4. The method as claimed in claim 1, wherein the drying temperature in step 3) is 100-300 ℃, and the drying time is 3-10 min; the pyrolysis temperature is 350-500 ℃, and the pyrolysis time is 3-10 min.

5. The method for preparing a lead-free thin film material using phase transition induction according to claim 1, wherein the 8-layer BCT-BMT thin film is prepared in the step 4).

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