CN109734441A

CN109734441A - A kind of narrow band gap bismuth layered intergrowth structure ferroelectric material and preparation method thereof

Info

Publication number: CN109734441A
Application number: CN201811542101.6A
Authority: CN
Inventors: 张发强; 刘志甫; 李永祥
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2018-12-17
Filing date: 2018-12-17
Publication date: 2019-05-10

Abstract

The present invention relates to a kind of low energy gap bismuth stratiform symbiotic structure ferroelectric material and preparation method thereof, the molecular formula of the low energy gap bismuth stratiform symbiotic structure ferroelectric material is Bi₄Ti₃O₁₂‑Bi₅Ti₃FeO₁₅；The low energy gap bismuth stratiform symbiotic structure ferroelectric material has the BiT-BTF superperiod structure of long-range order, Bi in the superperiod structure₄Ti₃O₁₂Single layer and Bi₅Ti₃FeO₁₅Single layer edgecAxis is alternately arranged.

Description

A kind of low energy gap bismuth stratiform symbiotic structure ferroelectric material and preparation method thereof

Technical field

The present invention relates to a kind of low energy gap bismuth stratiform symbiotic structure ferroelectric materials and preparation method thereof, belong to photoelectron material Material, catalysis material, Ferro-Electric Material and Element field.

Background technique

As the transition of the non-renewable energy resources such as petroleum, natural gas, coal consumes, Energy restructuring is sent out as human society Open up very important project of vital and lasting importance, the exploitation of renewable energy based on luminous energy, using technology increasingly by the concern of the whole society. Photovoltaic effect and photocatalysis are two kinds of leading forms that the mankind directly utilize solar energy, the former can directly convert luminous energy For electric energy, and the latter can realize hydrogen manufacturing using decomposing water with solar energy, and can apply to sewage treatment, therefore grind in new energy technology Occupy comparable status in hair.Research and development new material is the important directions of solar energy industry development, and forbidden bandwidth appropriate Then to evaluate the most key one of the index of associated materials, usually require that the forbidden bandwidth of material be preferably ranged from 1.0~1.8eV it Between.

As a kind of important functional material, ferroelectric material in information storage, is led to its distinctive spontaneous polarization properties The multiple fields such as news, pressure sensing, thermal imaging are widely used.The application of optoelectronic areas is that ferroelectric material is studied in recent years Another forward position direction, internal to there is very big internal electric field due to ferroelectric spontaneous polarization, size even compares p-n junction Built in field in photovoltaic cell wants big 1~2 magnitude, this characteristic makes ferroelectric material have separation light induced electron-sky The ability in cave pair, and show far the photovoltage output characteristics of super forbidden bandwidth and excellent photocatalysis performance.However, ferroelectricity The forbidden bandwidth of material usually in 2.5~3eV or more, needs ultraviolet light that can just inspire corresponding performance, thus light-use Rate is low, becomes the bottleneck of ferroelectric material related application.

Summary of the invention

In view of the above-mentioned problems, the limitation the present invention overcomes traditional ferroelectric material in forbidden bandwidth, provides a kind of narrow Bismuth stratiform symbiotic structure ferroelectric material of forbidden band and preparation method thereof.

On the one hand, the present invention provides a kind of low energy gap bismuth stratiform symbiotic structure ferroelectric material, the low energy gap bismuth stratiforms The molecular formula of symbiotic structure ferroelectric material is Bi₄Ti₃O₁₂-Bi₅Ti₃FeO₁₅；The low energy gap bismuth stratiform symbiotic structure ferroelectric material BiT-BTF superperiod structure with long-range order, Bi in the superperiod structure₄Ti₃O₁₂Single layer and Bi₅Ti₃FeO₁₅Single layer edge C-axis is alternately arranged.

Preferably, the Curie temperature of the low energy gap bismuth stratiform symbiotic structure ferroelectric material is 730~750 DEG C, material Forbidden bandwidth is 0.8~0.9eV；Preferably, the curie point of the low energy gap bismuth stratiform symbiotic structure ferroelectric material is 745 DEG C, Forbidden bandwidth is 0.87eV.

On the other hand, the present invention provides a kind of preparation method of above-mentioned low energy gap bismuth stratiform symbiotic structure ferroelectric material, Include:

(1) Bi is weighed according to molar ratio 9:12:1₂O₃Powder, TiO₂Powder, Fe₂O₃Powder simultaneously mixes, and obtains solid mixture；

(2) it after being pre-sintered obtained solid mixture 4~8 hours at 750~820 DEG C, then is crushed, obtains intermediate powder 1；

(3) it after calcining powder 1 among gained 12~24 hours at 900~1050 DEG C, then is crushed, obtains intermediate powder 2；

(4) powder 2 among gained is repeated into step (3) at least 1 time (preferably at least 2 times), obtains BiT-BTF structure powder；

(5) it is granulated simultaneously compression moulding after mixing gained BiT-BTF structure powder, binder, obtains biscuit；

(6) by gained biscuit after dumping, after being sintered 1~6 hour at 1050~1150 DEG C, the low energy gap bismuth stratiform is obtained Symbiotic structure ferroelectric material.

In the disclosure, Bi is weighed₂O₃Powder, TiO₂Powder, Fe₂O₃Powder (according to molar ratio 9:12:1) simultaneously mixes, and obtains Solid mixture after being then pre-sintered 4~8 hours at 750~820 DEG C, then is crushed, obtains intermediate powder 1, straight to prevent Connect the volatilization of Bi caused by high-temperature calcination.Then after powder 1 among gained being calcined 12~24 hours at 900~1050 DEG C, then It is crushed, obtains intermediate powder 2, continue to repeat this step at least 1 time (preferably 2~3 times), utilize crushing (such as ball repeatedly Mixer mill) and calcination process promote the homogenization of mi-crochemistry composition, so that obtaining has long-range order BiT-BTF coexisting phase BiT-BTF structure powder.It is granulated simultaneously compression moulding after finally mixing gained BiT-BTF structure powder, binder, then through arranging Glue, and after being sintered 1~6 hour at 1050~1150 DEG C, obtain the low energy gap bismuth stratiform symbiotic structure ferroelectric material.

Preferably, in step (1), the Bi₂O₃The partial size of powder is 50nm~2 μm；The TiO₂The partial size of powder is 50nm~1 μm；The Fe₂O₃The partial size of powder is 50nm~1 μm.

Preferably, weighing the Bi in step (1)₂O₃Excessive 1~5mol% when powder.

Preferably, the mode of the crushing is ball milling mixing in step (2) and step (3)；The revolving speed of the ball milling mixing It is 400~1000 revs/min, the time is 6~12 hours.

Preferably, the binder is PVAC polyvinylalcohol, polyvinyl formal PVB and polymerized thylene carbonate in step (4) At least one of third rouge PPC, additional amount are 5~10wt% of BiT-BTF structure powder quality.

Preferably, in step (5), the mode of the compression moulding be it is dry-pressing formed, the dry-pressing formed pressure is 10 ~240MPa.

Preferably, the temperature of the dumping is 550~650 DEG C in step (6), the time is 1~2 hour.

Preferably, the temperature of the calcining of the intermediate powder 2 is stepped up according to the number of calcining, to promote micro components With the homogenization of structure.

The bismuth stratiform symbiotic structure material of above method preparation of the present invention, molecular formula Bi₄Ti₃O₁₂-Bi₅Ti₃FeO₁₅, The material be it is single-phase, with long-range order symbiotic structure (BiT-BTF superperiod structure), crystal grain is in the form of sheets；And the material has There is apparent ferroelectric properties, Curie temperature is up to 745 DEG C；Simultaneously as heterogeneous interface absorbs between BiT layers and BTF layers, above-mentioned length The symbiotic structure of Cheng Youxu also makes its forbidden bandwidth be 0.87eV, is a kind of well below the forbidden bandwidth of conven-tional ferroelectric body Multifunctional material with bright prospects, especially ferroelectricity photovoltaic, in terms of application.

Detailed description of the invention

Fig. 1 is the XRD diagram piece of intermediate powder 2 and BiT-BTF structure powder in the embodiment of the present invention 1；

Fig. 2 a is the SEM figure of BiT-BTF ceramics in embodiment 1；

Fig. 2 b is the TEM High-Resolution Map of intermediate powder 2 in embodiment 1, intermediate powder 3 and BiT-BTF ceramics；

Fig. 3 a is the ferroelectric hysteresis loop of BiT-BTF ceramics in embodiment 1；

Fig. 3 b is dielectric constant, the dielectric loss temperature spectrogram of BiT-BTF ceramics in embodiment 1；

Fig. 4 is the reflectance spectrum of BiT-BTF ceramics in embodiment 1.

Specific embodiment

The present invention is further illustrated below by way of following embodiments, it should be appreciated that following embodiments are merely to illustrate this Invention, is not intended to limit the present invention.

In the disclosure, the molecular formula of low energy gap bismuth stratiform symbiotic structure ferroelectric material is Bi₄Ti₃O₁₂-Bi₅Ti₃FeO₁₅ (BiT-BTF), composition is single-phase, has ferroelectric properties, and BiT single layer and BTF single layer are alternately arranged along c-axis by 1:1 in structure, brilliant Grain is in the form of sheets.The material has ferroelectric properties, and Curie temperature is 730~750 DEG C, and the forbidden bandwidth of material is 0.8~0.9eV, Far below traditional ferroelectric material, absorption can be generated to infrared light.

In an embodiment of the present invention, using the Bi of multistep sintering synthetic method preparation pure phase₄Ti₃O₁₂- Bi₅Ti₃FeO₁₅Low energy gap bismuth stratiform symbiotic structure ferroelectric material.Illustrate to following exemplary low energy gap bismuth stratiform symbiotic structure iron The preparation method of electric material.

At room temperature, stoichiometrically 9:12:1 weighs powdered Bi₂O₃Powder, TiO₂Powder, Fe₂O₃Powder simultaneously mixes, Obtain solid mixture.In alternative embodiments, Bi₂O₃The partial size of powder can be 50nm~2 μm.TiO₂The partial size of powder It can be 50nm~1 μm.Fe₂O₃The partial size of powder can be 50nm~1 μm.Wherein, Bi₂O₃Excessive 1~5mol% is to make up high temperature burning The volatilization of Bi during knot.As an example, stoichiometrically 7:14:1 weighs powdered Bi₂O₃、TiO₂、Fe₂O₃Later, Addition ethyl alcohol, ball milling 6~12 hours (revolving speed is 400~1000 revs/min), and dried in 100 ± 10 DEG C, obtain solid mixing Object.

Solid mixture is pre-sintered 4~8 hours at 750~820 DEG C, obtains blocky Bi₄Ti₃O₁₂(BiT) and Bi₅Ti₃FeO₁₅(BTF) mixture.By blocky Bi₄Ti₃O₁₂(BiT) and Bi₅Ti₃FeO₁₅(BTF) mixture is broken, crosses 40 meshes, Ethyl alcohol is added, ball milling 6~12 hours (revolving speed is 400~1000 revs/min), is dried later in 100 DEG C, obtains intermediate powder 1.

By intermediate powder 1 respectively at 900~1050 DEG C after multiple (at least 2 times) " calcining+ball milling ", intermediate powder is obtained 2,3,4 ... .. are until obtain pure BiT-BTF structure powder.It should be noted that the BiT-BTF through repeatedly sintering pre-synthesis long-range order During structure powder, fine grinding is carried out to powder before calcining every time, ball mill revolves 400~1000 revs/min of revolving speed, the time It is 6~12 hours.In addition, intermediate powder 2, intermediate powder 3, intermediate powder 4 ... .. calcining temperature according to calcining number Gradually increase between 900~1050 DEG C, to promote the homogenization of micro components and structure.

After BiT-BTF structure powder and binder appropriate (for example, PVA, PVB, PPC etc.) mixing granulation, in 10- It is tabletted under 200Mpa pressure, obtain sheet sample (biscuit).

Sheet sample is fitted into crucible to be placed in Muffle furnace, in 600 ± 50 DEG C of dumping 1h, is warming up to 1100 ± 50 DEG C later Sintering 1~6 hour, Temperature fall, finally obtaining molecular formula is Bi₄Ti₃O₁₂-Bi₅Ti₃FeO₁₅Long-range order bismuth stratiform it is total Raw structure ferroelectric material.

Enumerate embodiment further below with the present invention will be described in detail.It will similarly be understood that following embodiment is served only for this Invention is further described, and should not be understood as limiting the scope of the invention, those skilled in the art is according to this hair Some nonessential modifications and adaptations that bright above content is made all belong to the scope of protection of the present invention.Following examples are specific Technological parameter etc. is also only an example in OK range, i.e. those skilled in the art can be done properly by the explanation of this paper In the range of select, and do not really want to be defined in hereafter exemplary specific value.

Embodiment 1

Specific embodiment of the invention conventional solid-state method synthesizes Bi by 5 pre-burnings₄Ti₃O₁₂-Bi₅Ti₃FeO₁₅After powder, Bismuth stratiform symbiotic structure Bi is produced in sintering₄Ti₃O₁₂-Bi₅Ti₃FeO₁₅Ceramics, comprising the following steps:

(1) at room temperature, Bi is weighed by afore mentioned chemical metering ratio₂O₃(99.9%) powder, TiO₂(99.6%) powder, Fe₂O₃It is (pure Spend 99.0%) powder, wherein Bi₂O₃Powder excess 5mol% is to make up the volatilization of Bi in high-temperature sintering process.Later, second is added Alcohol ball milling 12 hour, obtained liquid mixture is dried in 100 DEG C, obtains solid mixture；

(2) aforesaid solid is blended in 800 DEG C to be pre-sintered 7 hours, obtains blocky intermediate product；

(3) aforementioned block is crushed, excessively 40 meshes, addition ethyl alcohol, ball milling 12 hours, 450 revs/min of ball mill revolution speed.It Obtained liquid mixture is dried in 100 DEG C afterwards, obtains intermediate powder 1；

(4) aforementioned intermediate powder 1 is calcined 12~24 hours at 900 DEG C, obtains blocky intermediate product；

(5) blocky intermediate product obtained by step (4) is repeated into abovementioned steps (3), obtains intermediate powder 2；

(6) aforementioned intermediate 2 body of powder is calcined 12~24 hours at 940 DEG C, obtains blocky intermediate product；

(7) blocky intermediate product obtained by step (6) is repeated into abovementioned steps (3), obtains intermediate powder 3；

(8) aforementioned intermediate powder 3 is calcined 12~24 hours at 980 DEG C, obtains blocky intermediate product；

(9) blocky intermediate product obtained by step (8) is repeated into abovementioned steps (3), obtains intermediate powder 4；

(10) aforementioned intermediate 4 body of powder is calcined 12~24 hours at 1020 DEG C, obtains block product, which has long-range order Symbiotic structure feature；

(11) block product obtained by step (10) is repeated into abovementioned steps (3), obtains the BiT-BTF structure powder of long-range order；

(12) tabletted under 10-200Mpa pressure by after aforementioned BiT-BTF structure powder and PVA mixing granulation appropriate. Sheet sample is fitted into crucible to be placed in Muffle furnace, the dumping 1h at 600 DEG C, it is small to be warming up to 1100 ± 50 DEG C of sintering 1~6 later When, Temperature fall, finally obtaining molecular formula is Bi₄Ti₃O₁₂-Bi₅Ti₃FeO₁₅Long-range order bismuth stratiform symbiotic structure ferroelectricity pottery Porcelain sample (BiT-BTF ceramics sample).

The ceramic structure for using the above method to prepare is single-phase, the microcosmic upper symbiotic structure feature with long-range order, BiT Layer (Bi₄Ti₃O₁₂Layer) and BTF layers of (Bi₅Ti₃FeO₁₅Layer) it is alternately arranged along c-axis, crystal grain is grown in the form of sheets.Sample is ferroelectricity material Material has the forbidden bandwidth far below conven-tional ferroelectric body, is a kind of ferroelectric type photoelectron with broad prospect of application, photocatalysis Material.

Using the XRD of intermediate powder 2 obtained in embodiment and BiT-BTF structure powder as shown in Figure 1, due to it is microcosmic at Divide and homogenization has not yet been reached in structure, the superperiod diffraction of long-range order BiT-BTF coexisting phase is not observed in intermediate powder 2 Peak, through there is superperiod diffraction maximum in ball milling repeatedly, sintered BiT-BTF structure powder, and without other miscellaneous peaks.

SEM spectrum using BiT-BTF ceramics sample obtained in embodiment is as shown in Figure 2 a, and grain growth is good, table Reveal the typical strip-like features of bismuth stratified material.Fig. 2 b gives intermediate powder 2, intermediate powder 3 and BiT-BTF ceramics sample and hangs down Directly in the TEM high resolution picture in superperiod direction, as can be seen from the figure: there are apparent ingredient and structure are uneven for intermediate powder 2 It is even；The homogeneity of ingredients of intermediate powder 3 is taken on a new look, it can be seen that there are Bi₄Ti₃O₁₂Single layer and Bi₅Ti₃FeO₁₅Single layer is along c-axis It is alternately arranged, but still it is observed that the structure entanglement of part；BiT-BTF structure powder is able to observe that the BiT- of long-range order BTF superperiod, BiT single layer are alternately arranged with BTF single layer along c-axis.

Fig. 3 a gives the ferroelectric hysteresis loop figure of BiT-BTF ceramics sample, is observed that apparent hysteresis on figure, says Bright material is a kind of ferroelectric material.Fig. 3 b is the dielectric constant and loss thermogram of BiT-BTF ceramics sample, can be seen on spectrogram Two abnormal Dielectric peaks are observed, the structural adjustment that low temperature peak is BiT layers, high temperature peak corresponds to Curie transition, therefore the Curie of material Point is 745 DEG C, is a kind of high-Curie-point ferroelectric material.

Optical absorption characteristics using BiT-BTF ceramics sample made from embodiment are as shown in Figure 4, it can be seen that material exists There are three apparent ABSORPTION EDGEs in test scope, the forbidden bandwidth of long wave position respective material, magnitude 0.87eV, the value is remote Far below the forbidden bandwidth of 2.5~3eV of conven-tional ferroelectric material.

Finally it is noted that the above specific embodiment is only used to illustrate the technical scheme of the present invention rather than is limited, Although being described the invention in detail referring to preferred embodiment, those skilled in the art should understand that, it can be right Technical solution of the present invention is modified or replaced equivalently, without departing from the spirit and scope of the technical solution of the present invention, It is intended to be within the scope of the claims of the invention.

Claims

1. a narrow band gap bismuth layered intergrowth structure ferroelectric material, is characterized in that, the molecular formula of the narrow band gap bismuth layered intergrowth structure ferroelectric material is Bi ₄ Ti ₃ O ₁₂ -Bi ₅ Ti ₃ FeO ₁₅ ; The narrow band gap bismuth layered intergrowth structure ferroelectric material has a long _- range ordered _BiT _- BTF superperiodic structure, and the _Bi4Ti3O12 monolayer and the _Bi5Ti3FeO15 monolayer in the superperiodic structure are along _c The axes are arranged alternately.

2 . The ferroelectric material with a narrow forbidden band bismuth layered intergrowth structure according to claim 1 , wherein the Curie temperature of the narrow forbidden band bismuth layered intergrowth structure ferroelectric material is 730-750° C. The forbidden band width is 0.8-0.9 eV; preferably, the Curie point of the narrow band gap bismuth layered intergrowth structure ferroelectric material is 745° C., and the forbidden band width is 0.87 eV.

3. a preparation method of narrow band gap bismuth layered intergrowth structure ferroelectric material as claimed in claim 1 or 2, is characterized in that, comprising:

(1) Weigh and mix Bi ₂ O ₃ powder, TiO ₂ powder and Fe ₂ O ₃ powder according to the molar ratio of 9:12:1 to obtain a solid mixture;

(2) Pre-sintering the obtained solid mixture at 750-820° C. for 4-8 hours, and then pulverizing to obtain Intermediate Powder 1;

(3) after calcining the obtained intermediate powder 1 at 900-1050° C. for 12-24 hours, and then pulverizing to obtain the intermediate powder 2;

(4) repeating step (3) at least once with the obtained intermediate powder 2 to obtain a BiT-BTF structure powder;

(5) Mixing the obtained BiT-BTF structure powder and the binder, granulating and pressing to obtain a green body;

(6) After the obtained green body is debonded and sintered at 1050-1150° C. for 1-6 hours, the narrow-gap bismuth layered intergrowth structure ferroelectric material is obtained.

4 . The preparation method according to claim 3 , wherein in step (1), the particle size of the Bi ₂ O ₃ powder is 50 nm to 2 μm; the particle size of the TiO ₂ powder is 50 nm to 2 μm. 5 . 1 μm; the particle size of the Fe ₂ O ₃ powder is 50 nm to 1 μm.

The preparation method according to claim 3 or 4, characterized in that, in step (1), the Bi ₂ O ₃ powder is weighed in excess of 1-5 mol%.

6. The preparation method according to any one of claims 3-5, characterized in that, in steps (2) and (3), the pulverizing method is ball milling mixing; the rotation speed of the ball milling mixing is 400-1000 rpm rev/min, and the time is 6 to 12 hours.

7. The preparation method according to any one of claims 3-6, wherein in step (4), the binder is polyvinyl alcohol PVA, polyvinyl formal PVB and polypropylene carbonate PPC At least one of them is added in an amount of 5-10wt% of the mass of the BiT-BTF structure powder.

8 . The preparation method according to claim 3 , wherein, in step (5), the pressing method is dry pressing, and the pressure of the dry pressing is 10-240 MPa. 9 .

9 . The preparation method according to claim 3 , wherein in step (6), the temperature of the debinding is 550-650° C. and the time is 1-2 hours. 10 .

10 . The preparation method according to claim 3 , wherein the calcination temperature of the intermediate powder 2 is gradually increased according to the number of calcinations, so as to promote the homogenization of microscopic components and structures. 11 .