CN115504503B - Niobium-doped cubic phase two-dimensional flaky strontium titanate material and preparation method thereof - Google Patents

Niobium-doped cubic phase two-dimensional flaky strontium titanate material and preparation method thereof Download PDF

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CN115504503B
CN115504503B CN202211174655.1A CN202211174655A CN115504503B CN 115504503 B CN115504503 B CN 115504503B CN 202211174655 A CN202211174655 A CN 202211174655A CN 115504503 B CN115504503 B CN 115504503B
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niobium
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秦毅
王子旭
黄锐
郗红艳
赵婷
朱建锋
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Shaanxi University of Science and Technology
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Abstract

The invention discloses a niobium-doped cubic phase two-dimensional flaky strontium titanate material and a preparation method thereof, comprising the following steps: synthesis of BaNb by vacuum solid phase reaction x Ti (1‑x) O 3 The method comprises the steps of carrying out a first treatment on the surface of the Wherein x=0 to 0.28, 8; with TiO 2 And BaNb x Ti (1‑x) O 3 Synthesizing flaky Ba by using molten salt method as raw material 6 Nb x Ti (17‑x) O 40 The method comprises the steps of carrying out a first treatment on the surface of the In BaCO 3 And sheet-like Ba 6 Nb x Ti (17‑x) O 40 As raw material, adopting molten salt method to synthesize cubic phase flaky BaNb x Ti (1‑x) O 3 The method comprises the steps of carrying out a first treatment on the surface of the By SrCl 2 And cubic photo-like BaNb x Ti (1‑x) O 3 As raw material, adopting molten salt method to synthesize cubic phase lamellar SrNb x Ti (1‑x) O 3 . The invention adopts a topological structure evolution process, and reserves the equiaxial crystal system structure of strontium titanate in the two-dimensional and semiconducting processes, thereby widening the application of the strontium titanate doped material.

Description

Niobium-doped cubic phase two-dimensional flaky strontium titanate material and preparation method thereof
Technical Field
The invention belongs to the field of inorganic metal oxide perovskite two-dimensional materials and thermoelectric materials in material disciplines, and relates to a niobium-doped cubic phase two-dimensional flaky strontium titanate material and a preparation method thereof.
Background
The thermoelectric material can convert heat energy into electric energy, improves the energy utilization rate, improves the energy crisis and the environmental problem, and is the best choice for directly utilizing the heat energy to generate electricity. ZT value for thermoelectric conversion efficiency (zt=s 2 sigma/K, S, sigma, K are Seebeck coefficient, electrical conductivity, thermal conductivity, respectively). Strontium titanate is used as a typical high-temperature oxide thermoelectric material, has higher Seebeck coefficient and excellent high-temperature stability, is easy to obtain from the nature, is nontoxic, does not contain rare earth elements, and can improve the conductivity by doping, so that the application prospect is very wide.
Because the cubic phase strontium titanate belongs to an equiaxed crystal system and has a perovskite structure, the cubic phase strontium titanate powder material prepared by the conventional method is equiaxed crystal particles with cubic block-shaped geometric shapes. However, thermoelectric material-related studies have shown that low-dimensionalization can greatly improve the electric transport property of materials, while bulk thermoelectric materials with orientation (i.e., bulk thermoelectric materials with textured structures) prepared from micro-nano powders with two-dimensional geometry can provide a large number of phonon scattering interfaces, thereby improving the heat transport property of bulk thermoelectric materials. Therefore, for preparing high-performance strontium titanate block thermoelectric materials, it is important to prepare powder of niobium-doped cubic phase strontium titanate and having lamellar two-dimensional geometric shape. At present, a lot of methods for preparing the strontium titanate doped with isometric crystal particles with cubic block geometry are usually adopted for preparation by adopting methods such as solid phase reaction, chemical coprecipitation, sol-gel technology, hydrothermal synthesis and the like, but no preparation method is available at present, so that the strontium titanate has a cubic crystal structure and a two-dimensional lamellar geometry, and meanwhile, the strontium titanate doped with the strontium titanate has the characteristic of doping semi-conductivity.
Disclosure of Invention
The invention aims to solve the problem that the two-dimensional shape of an isometric crystal system doped strontium titanate powder is difficult, and provides a niobium doped cubic phase two-dimensional flaky strontium titanate material and a preparation method thereof.
The invention is realized by the following technical scheme:
a preparation method of a niobium-doped cubic two-dimensional flaky strontium titanate material comprises the following steps:
s1, synthesizing BaNb by a vacuum solid phase reaction method x Ti (1-x) O 3 The method comprises the steps of carrying out a first treatment on the surface of the Wherein x=0-0.28;
s2, to obtain BaNb x Ti (1-x) O 3 With TiO 2 Synthesizing flaky Ba by using molten salt method as raw material 6 Nb x Ti (17-x) O 40 ；
S3, baCO 3 And the prepared flaky Ba 6 Nb x Ti (17-x) O 40 As a raw material by means of Ba 6 Nb x Ti (17-x) O 40 Is subjected to topological chemical transformation to obtain a cubic phase two-dimensional flaky BaNb x Ti (1-x) O 3 ；
S4, preparing the cubic phase two-dimensional flaky BaNb x Ti (1-x) O 3 And SrCl 2 By means of the preservation of phase structure and geometric shape, the cubic phase two-dimensional sheet SrNb is obtained through the exchange and evolution of Sr element and Ba element x Ti (1-x) O 3 。
Preferably, step S1 specifically includes: in BaCO 3 、TiO 2 And Nb (Nb) 2 O 5 The method comprises the steps of mixing, grinding and presintering to obtain niobium doped barium titanate presintering powder, and then carrying out embedding burning and grinding treatment on the niobium doped barium titanate presintering powder in an argon atmosphere to obtain BaNb x Ti (1-x) O 3 。
Preferably, in step S1, baNb x Ti (1-x) O 3 To analytically pure BaCO 3 、TiO 2 And Nb (Nb) 2 O 5 Is prepared from BaCO 3 、TiO 2 、Nb 2 O 5 The molar ratio is 1: (1-x): 0.5x. The presintering temperature is 1150 ℃; the burial firing specifically comprises the following steps: the niobium doped barium titanate presintered powder is transferred into a crucible, covered by an inverted crucible, and buried around the crucible by charcoal powder, so that the whole crucible and presintered powder are in a reduced state, and the burying and burning temperature is 1300 ℃.
Preferably, step S2 specifically includes: by BaNb synthesized in step S1 x Ti (1-x) O 3 And analytically pure TiO 2 As a raw material, naCl and KCl mixed salt with the purity of 99.5 percent are used as a fused salt sintering medium; mixing the raw materials with a fused salt sintering medium, grinding, sintering in the fused salt medium, cleaning to remove fused salt, and drying to obtain a flaky Ba 6 Nb x Ti (17-x) O 40 。
Preferably, baNb x Ti (1-x) O 3 With TiO 2 The molar ratio is 6:11, the mass ratio of the raw materials to the fused salt sintering medium is 1:2, the mass ratio of NaCl and KCl in the mixed salt is 1:2.
Preferably, in S3, in the topological structure evolution process, the cubic phase two-dimensional flaky BaNb x Ti (1-x) O 3 Is synthesized by two-dimensional flaky Ba 6 Nb x Ti (17-x) O 40 And analytically pure BaCO 3 As a raw material, naCl with a purity of 99.5% was added as a raw materialBaCO is used as a fused salt sintering medium 3 Mixing with NaCl, grinding, and adding sheet Ba 6 Nb x Ti (17-x) O 40 Mixing (post-adding Ba 6 Nb x Ti (17-x) O 40 The reason for mixing is that the damage of long-time grinding to the flaky structure is avoided), and sintering is carried out after mixing; dissolving the sintered product under heating, separating, and oven drying to obtain cubic photo-like BaNb x Ti (1-x) O 3 The method comprises the steps of carrying out a first treatment on the surface of the Wherein Ba is 6 Nb x Ti (17-x) O 40 And BaCO 3 The molar ratio of (2) is 1:12, the mass ratio of the raw materials to the molten salt sintering medium is 1:2.
preferably, in S4, the cubic phase is a two-dimensional sheet of SrNb x Ti (1-x) O 3 Is synthesized by cubic phase two-dimensional flaky BaNb x Ti (1-x) O 3 And analytically pure SrCl 2 Adding NaCl with the purity of 99.5% as a fused salt sintering medium into the raw material, and adding SrCl 2 Mixing with NaCl, grinding, and adding cubic photo-like BaNb x Ti (1-x) O 3 Mixing (post-addition of cubic phase sheet BaNb) x Ti (1-x) O 3 The reason for mixing is to avoid damage to the sheet structure by long-time grinding), and sintering is performed after mixing. Dissolving the sintered product under heating, separating, and oven drying to obtain niobium doped cubic phase two-dimensional sheet SrNb x Ti (1-x) O 3 The method comprises the steps of carrying out a first treatment on the surface of the Wherein, the cubic phase two-dimensional flaky BaNb x Ti (1-x) O 3 And SrCl 2 The molar ratio is 1:10, the mass ratio of the raw materials to the molten salt sintering medium is 1:1.
preferably, S1 specifically includes: mixing, grinding and presintering analytically pure barium carbonate, titanium dioxide and niobium pentoxide; grinding the presintered powder, burying and burning charcoal powder in a vacuum tube furnace under argon atmosphere, and grinding to obtain BaNb x Ti (1-x) O 3 And (3) powder.
Preferably, S2 specifically includes: baNb is carried out x Ti (1-x) O 3 Mixing the powder with titanium dioxide, sodium chloride and potassium chlorideGrinding and sintering; dissolving the sintered product under water bath heating, separating, and oven drying to obtain sheet Ba 6 Nb x Ti (17-x) O 40 Powder;
preferably, S3 specifically includes: mixing barium carbonate with sodium chloride, grinding, and mixing with Ba 6 Nb x Ti (17-x) O 40 Mixing and sintering the powder; dissolving the sintered product under water bath heating, separating, and oven drying to obtain sheet BaNb x Ti (1-x) O 3 Powder;
preferably, S4 specifically includes: mixing strontium chloride and sodium chloride, grinding, and mixing with sheet BaNb x Ti (1-x) O 3 Mixing and sintering; dissolving the sintered product under water bath heating, separating, and oven drying to obtain final product SrNb x Ti (1-x) O 3 。
Compared with the prior art, the invention has the following beneficial effects:
barium titanate and strontium titanate have similar crystal structures and atomic arrangement, are both cubic phases obtained by sintering under conventional conditions, and in the process of preparing the barium titanate, excessive titanium dioxide and the barium titanate form a lamellar second phase Ba 6 Ti 17 O 40 ，Ba 6 Ti 17 O 40 The (001) crystal face of the barium titanate is similar to the (111) crystal face atomic structure of the barium titanate, and based on the (001) crystal face atomic structure, the invention utilizes the evolution mechanism of the topological structure under the high temperature condition, and adds barium ions under the high temperature condition to enable lamellar second phase Ba 6 Ti 17 O 40 TiO in precursor 5 ]Pentahedron and [ TiO ] 6 ]The octahedron is changed from the common edge connection to the more stable common top connection, and on the basis of keeping the lamellar structure,<001>conversion of oriented precursor to<111>Oriented barium titanate (cubic phase barium titanate) to obtain a sheet-like BaTiO 3 Then by ABO 3 Cation element exchange at A position in perovskite structure is carried out by<111>Evolution of oriented barium titanate into<111>Oriented cubic two-dimensional platelet strontium titanate. Thereby realizing that the prepared strontium titanate has two-dimensional flaky shape under the condition of not changing the cubic phase crystal structure of the strontium titanateIs a geometric feature of (2).
Further, niobium doping is performed in the preparation process of precursor raw material barium titanate, and the niobium doping characteristic is kept in the topological structure evolution process, so that the semiconducting of cubic phase two-dimensional flaky strontium titanate is realized, the electric transport property of the cubic phase two-dimensional flaky strontium titanate is improved, the preparation method can be applied to the preparation of block strontium titanate thermoelectric materials with textured tissues, the preparation and application ideas of the strontium titanate materials are widened, and a material foundation is laid for the development of novel strontium titanate composite thermoelectric materials.
Drawings
FIG. 1 is a SEM topography photograph of examples 1,3,5, respectively;
FIG. 2 is an XRD pattern for example 3;
FIG. 3 is an EDS element distribution map of example 3;
fig. 4 is a graph showing the resistivity measurements and their trends with Nb doping levels for examples 1 to 5.
Detailed Description
For a further understanding of the present invention, the present invention is described below in conjunction with the following examples, which are provided to further illustrate the features and advantages of the present invention and are not intended to limit the claims of the present invention.
Example 1
Step one: preparation of BaNb x Ti (1-x) O 3
(1) Mixing barium carbonate, titanium dioxide and niobium pentoxide according to a molar ratio of 1:1:0 (i.e. x=0), grinding for 2 hours, presintering in a muffle furnace, presintering at 1150 ℃, and preserving heat for 4 hours;
(2) Grinding the presintered powder for 1 hour, burying in a tube furnace under argon atmosphere at 1300 ℃ for 5 hours to obtain BaNb x Ti (1-x) O 3 。
Step two: preparation of Ba 6 Nb x Ti (17-x) O 40
(1) BaNb after being buried and burned x Ti (1-x) O 3 Mixing the powder with titanium dioxide, sodium chloride and potassium chloride, grinding for 2 hours, sintering at 1150 ℃ and preserving heat for 5 hoursWhen in use; baNb (BaNb) x Ti (1-x) O 3 The mol ratio of the powder to the titanium dioxide is 6:11, and BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the titanium dioxide to the total amount of the sodium chloride and the potassium chloride is 1:2, and the mass ratio of the sodium chloride to the potassium chloride is 1:2;
(2) Dissolving the sintered product under heating in water bath, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain Ba 6 Nb x Ti (17-x) O 40 。
Step three: preparation of sheet BaNb x Ti (1-x) O 3
(1) Drying the dried Ba 6 Nb x Ti (17-x) O 40 Mixing the powder with barium carbonate and sodium chloride, grinding for 2 hours, and mixing with Ba 6 Nb x Ti (17-x) O 40 Mixing the powder in a mixer for 6 hours, sintering at 1150 ℃ for 4 hours; ba (Ba) 6 Nb x Ti (17-x) O 40 The mol ratio of the powder to the barium carbonate is 1:12, ba 6 Nb x Ti (17-x) O 40 The mass ratio of the total amount of the powder and the barium carbonate to the sodium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain sheet BaNb x Ti (1-x) O 3 。
Step four: preparation of sheet SrNb x Ti (1-x) O 3
(1) Drying the dried flaky BaNb x Ti (1-x) O 3 Mixing the powder with strontium chloride and sodium chloride, grinding for 2 hours, and mixing with sheet BaNb x Ti (1-x) O 3 Mixing in a mixer for 6 hours, sintering at 1100 ℃ for 5 hours; sheet BaNb x Ti (1-x) O 3 The mol ratio of the powder to the strontium chloride is 1:10, and the flaky BaNb is a flaky BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the strontium chloride to the sodium chloride is1:1；
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm separating core, and oven drying at 60deg.C to obtain final product sheet SrNb x Ti (1-x) O 3 。
Example 2
Step one: preparation of BaNb x Ti (1-x) O 3
(1) Mixing barium carbonate, titanium dioxide and niobium pentoxide according to a molar ratio of 1:0.8583:0.0708 (i.e. x=0.07), grinding for 2 hours, presintering in a muffle furnace, presintering at 1150 ℃ and preserving heat for 4 hours;
(2) Grinding the presintered powder for 1 hour, burying in a tube furnace under argon atmosphere at 1300 ℃ for 5 hours to obtain BaNb x Ti (1-x) O 3 。
Step two: preparation of Ba 6 Nb x Ti (17-x) O 40
(1) BaNb after being buried and burned x Ti (1-x) O 3 Mixing the powder with titanium dioxide, sodium chloride and potassium chloride, grinding for 2 hours, sintering at 1150 ℃ and preserving heat for 5 hours; baNb (BaNb) x Ti (1-x) O 3 The mol ratio of the powder to the titanium dioxide is 6:11, and BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the titanium dioxide to the total amount of the sodium chloride and the potassium chloride is 1:2, and the mass ratio of the sodium chloride to the potassium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl and KCl mixed salt, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain Ba 6 Nb x Ti (17-x) O 40 。
Step three: preparation of sheet BaNb x Ti (1-x) O 3
(1) Drying the dried Ba 6 Nb x Ti (17-x) O 40 Mixing the powder with barium carbonate and sodium chloride, grinding for 2 hours, and mixing with Ba 6 Nb x Ti (17-x) O 40 Mixing the powder in a mixer for 6 hours, sintering at 1150 ℃ for 4 hours; ba (Ba) 6 Nb x Ti (17-x) O 40 The mol ratio of the powder to the barium carbonate is 1:12, ba 6 Nb x Ti (17-x) O 40 The mass ratio of the total amount of the powder and the barium carbonate to the sodium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain sheet BaNb x Ti (1-x) O 3 。
Step four: preparation of sheet SrNb x Ti (1-x) O 3
(1) Drying the dried flaky BaNb x Ti (1-x) O 3 Mixing the powder with strontium chloride and sodium chloride, grinding for 2 hours, and mixing with sheet BaNb x Ti (1-x) O 3 Mixing in a mixer for 6 hours, sintering at 1100 ℃ for 5 hours; sheet BaNb x Ti (1-x) O 3 The mol ratio of the powder to the strontium chloride is 1:10, and the flaky BaNb is a flaky BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the strontium chloride to the sodium chloride is 1:1;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm separating core, and oven drying at 60deg.C to obtain final product sheet SrNb x Ti (1-x) O 3 。
Example 3
Step one: preparation of BaNb x Ti (1-x) O 3
(1) Mixing barium carbonate, titanium dioxide and niobium pentoxide according to a molar ratio of 1:0.7167:0.1417 (i.e. x=0.14), grinding for 2 hours, presintering in a muffle furnace, presintering at 1150 ℃ and preserving heat for 4 hours;
(2) Grinding the presintered powder for 1 hour, burying in a tube furnace under argon atmosphere at 1300 deg.C, and maintaining for 5 hoursObtaining BaNb x Ti (1-x) O 3 。
Step two: preparation of Ba 6 Nb x Ti (17-x) O 40
(1) BaNb after being buried and burned x Ti (1-x) O 3 Mixing the powder with titanium dioxide, sodium chloride and potassium chloride, grinding for 2 hours, sintering at 1150 ℃ and preserving heat for 5 hours; baNb (BaNb) x Ti (1-x) O 3 The mol ratio of the powder to the titanium dioxide is 6:11, and BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the titanium dioxide to the total amount of the sodium chloride and the potassium chloride is 1:2, and the mass ratio of the sodium chloride to the potassium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl and KCl mixed salt, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain Ba 6 Nb x Ti (17-x) O 40 。
Step three: preparation of sheet BaNb x Ti (1-x) O 3
(1) Drying the dried Ba 6 Nb x Ti (17-x) O 40 Mixing the powder with barium carbonate and sodium chloride, grinding for 2 hours, and mixing with Ba 6 Nb x Ti (17-x) O 40 Mixing the powder in a mixer for 6 hours, sintering at 1150 ℃ for 4 hours; ba (Ba) 6 Nb x Ti (17-x) O 40 The mol ratio of the powder to the barium carbonate is 1:12, ba 6 Nb x Ti (17-x) O 40 The mass ratio of the total amount of the powder and the barium carbonate to the sodium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain sheet BaNb x Ti (1-x) O 3 。
Step four: preparation of sheet SrNb x Ti (1-x) O 3
(1) Drying the dried flaky BaNb x Ti (1-x) O 3 Mixing the powder with strontium chloride and sodium chloride, grinding for 2 hours, and mixing with sheet BaNb x Ti (1-x) O 3 Mixing in a mixer for 6 hours, sintering at 1100 ℃ for 5 hours; sheet BaNb x Ti (1-x) O 3 The mol ratio of the powder to the strontium chloride is 1:10, and the flaky BaNb is a flaky BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the strontium chloride to the sodium chloride is 1:1;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm separating core, and oven drying at 60deg.C to obtain final product sheet SrNb x Ti (1-x) O 3 。
Example 4
Step one: preparation of BaNb x Ti (1-x) O 3
(1) Mixing barium carbonate, titanium dioxide and niobium pentoxide according to a molar ratio of 1:0.5750:0.2125 (i.e. x=0.21), grinding for 2 hours, presintering in a muffle furnace, presintering at 1150 ℃ and preserving heat for 4 hours;
(2) Grinding the presintered powder for 1 hour, burying in a tube furnace under argon atmosphere at 1300 ℃ for 5 hours to obtain BaNb x Ti (1-x) O 3 。
Step two: preparation of Ba 6 Nb x Ti (17-x) O 40
(1) BaNb after being buried and burned x Ti (1-x) O 3 Mixing the powder with titanium dioxide, sodium chloride and potassium chloride, grinding for 2 hours, sintering at 1150 ℃ and preserving heat for 5 hours; baNb (BaNb) x Ti (1-x) O 3 The mol ratio of the powder to the titanium dioxide is 6:11, and BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the titanium dioxide to the total amount of the sodium chloride and the potassium chloride is 1:2, and the mass ratio of the sodium chloride to the potassium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, and cleaning with deionized water for multiple times to remove residual NaCl and residual NaCl in the productSeparating KCl mixed salt with 5000 rpm separating core, and oven drying at 60deg.C to obtain Ba 6 Nb x Ti (17-x) O 40 。
Step three: preparation of sheet BaNb x Ti (1-x) O 3
(1) Drying the dried Ba 6 Nb x Ti (17-x) O 40 Mixing the powder with barium carbonate and sodium chloride, grinding for 2 hours, and mixing with Ba 6 Nb x Ti (17-x) O 40 Mixing the powder in a mixer for 6 hours, sintering at 1150 ℃ for 4 hours; ba (Ba) 6 Nb x Ti (17-x) O 40 The mol ratio of the powder to the barium carbonate is 1:12, ba 6 Nb x Ti (17-x) O 40 The mass ratio of the total amount of the powder and the barium carbonate to the sodium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain sheet BaNb x Ti (1-x) O 3 。
Step four: preparation of sheet SrNb x Ti (1-x) O 3
(1) Drying the dried flaky BaNb x Ti (1-x) O 3 Mixing the powder with strontium chloride and sodium chloride, grinding for 2 hours, and mixing with sheet BaNb x Ti (1-x) O 3 Mixing in a mixer for 6 hours, sintering at 1100 ℃ for 5 hours; sheet BaNb x Ti (1-x) O 3 The mol ratio of the powder to the strontium chloride is 1:10, and the flaky BaNb is a flaky BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the strontium chloride to the sodium chloride is 1:1;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm separating core, and oven drying at 60deg.C to obtain final product sheet SrNb x Ti (1-x) O 3 。
Example 5
Step one: preparation of BaNb x Ti (1-x) O 3
(1) Mixing barium carbonate, titanium dioxide and niobium pentoxide according to a molar ratio of 1:0.4334:0.2833 (i.e. x=0.28), grinding for 2 hours, presintering in a muffle furnace, presintering at 1150 ℃ and preserving heat for 4 hours;
(2) Grinding the presintered powder for 1 hour, burying in a tube furnace under argon atmosphere at 1300 ℃ for 5 hours to obtain BaNb x Ti (1-x) O 3 。
Step two: preparation of Ba 6 Nb x Ti (17-x) O 40
(1) BaNb after being buried and burned x Ti (1-x) O 3 Mixing the powder with titanium dioxide, sodium chloride and potassium chloride, grinding for 2 hours, sintering at 1150 ℃ and preserving heat for 5 hours; baNb (BaNb) x Ti (1-x) O 3 The mol ratio of the powder to the titanium dioxide is 6:11, and BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the titanium dioxide to the total amount of the sodium chloride and the potassium chloride is 1:2, and the mass ratio of the sodium chloride to the potassium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl and KCl mixed salt, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain Ba 6 Nb x Ti (17-x) O 40 。
Step three: preparation of sheet BaNb x Ti (1-x) O 3
(1) Drying the dried Ba 6 Nb x Ti (17-x) O 40 Mixing the powder with barium carbonate and sodium chloride, grinding for 2 hours, and mixing with Ba 6 Nb x Ti (17-x) O 40 Mixing the powder in a mixer for 6 hours, sintering at 1150 ℃ for 4 hours; ba (Ba) 6 Nb x Ti (17-x) O 40 The mol ratio of the powder to the barium carbonate is 1:12, ba 6 Nb x Ti (17-x) O 40 Powder and barium carbonate totalThe mass ratio of the amount to the sodium chloride is 1:2;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm/separating core, and oven drying at 60deg.C to obtain sheet BaNb x Ti (1-x) O 3 。
Step four: preparation of sheet SrNb x Ti (1-x) O 3
(1) Drying the dried flaky BaNb x Ti (1-x) O 3 Mixing the powder with strontium chloride and sodium chloride, grinding for 2 hours, and mixing with sheet BaNb x Ti (1-x) O 3 Mixing in a mixer for 6 hours, sintering at 1100 ℃ for 5 hours; sheet BaNb x Ti (1-x) O 3 The mol ratio of the powder to the strontium chloride is 1:10, and the flaky BaNb is a flaky BaNb x Ti (1-x) O 3 The mass ratio of the total amount of the powder and the strontium chloride to the sodium chloride is 1:1;
(2) Dissolving the sintered product under water bath heating, cleaning with deionized water for multiple times to remove residual NaCl in the product, separating with 5000 rpm separating core, and oven drying at 60deg.C to obtain final product sheet SrNb x Ti (1-x) O 3 。
The process parameters of the examples of the present invention are summarized in table 1.
The process parameters of the topology evolution process in the example of table 1;
characterization is carried out on the morphology, phase, composition and electric transport performance of the niobium-doped cubic two-dimensional flaky strontium titanate prepared in the embodiment, and fig. 1 is an SEM morphology graph of the niobium-doped cubic two-dimensional flaky strontium titanate powder prepared in the embodiments 1,3 and 5, wherein the powder with a two-dimensional flaky structure is observed in all samples, but the powder prepared in the embodiment 5 has higher purity (containing less unreacted and grown nano particles) and larger thickness-to-diameter ratio; XRD phase and EDS element composition analysis are carried out on the sample prepared in the example 3 at random, and as shown in fig. 2 and 3, the phase is a standard cubic phase, and the existence of Nb, sr, ti, O and other elements can be clearly observed in an EDS spectrum, so that the chemical composition of a target product is met. Meanwhile, the powder prepared in examples 1 to 5 was subjected to tabletting test for conductivity, and as shown in fig. 4, the conductivity of the niobium-doped cubic phase two-dimensional flaky strontium titanate was enhanced with the increase of the Nb doping amount, and the transition from the insulating state to the semiconductor state was exhibited, which completely meets the rule of enhancing the conductivity of the titanic acid with the increase of the doping amount, namely, the conductivity was controlled by the doping amount. In summary, the invention is feasible to prepare niobium-doped cubic-phase two-dimensional flaky strontium titanate through a topological structure evolution process.

Claims (10)

1. The preparation method of the niobium-doped cubic two-dimensional flaky strontium titanate material is characterized by comprising the following steps of:
s1, synthesizing BaNb by a vacuum solid phase reaction method x Ti (1-x) O 3 The method comprises the steps of carrying out a first treatment on the surface of the Wherein x=0 to 0.28;
s2, tiO 2 And BaNb synthesized in step S1 x Ti (1-x) O 3 Synthesizing flaky Ba by using molten salt method as raw material 6 Nb x Ti (17-x) O 40 The method comprises the steps of carrying out a first treatment on the surface of the Wherein, baNb x Ti (1-x) O 3 With TiO 2 The molar ratio of (2) is 6:11;
s3, baCO 3 And the flaky Ba synthesized in the step S2 6 Nb x Ti (17-x) O 40 As raw material, adopting molten salt method to synthesize cubic phase flaky BaNb x Ti (1-x) O 3 The method comprises the steps of carrying out a first treatment on the surface of the Wherein, the tablet Ba 6 Nb x Ti （17-x） O 40 And BaCO 3 The molar ratio of (2) is 1:12;
s4, srCl 2 And the cubic phase flaky BaNb synthesized in the step S3 x Ti (1-x) O 3 As raw material, adopting molten salt method to synthesize cubic phase lamellar SrNb x Ti (1-x) O 3 The method comprises the steps of carrying out a first treatment on the surface of the Wherein, the sheet BaNb x Ti (1-x) O 3 And SrCl 2 The molar ratio of (2) is 1:10.
2. the method for preparing the niobium-doped cubic two-dimensional sheet strontium titanate material according to claim 1, wherein the step S1 specifically comprises: in BaCO 3 、TiO 2 And Nb (Nb) 2 O 5 The method comprises the steps of mixing, grinding and presintering to obtain niobium doped barium titanate presintering powder, and then carrying out embedding burning and grinding treatment on the niobium doped barium titanate presintering powder in an argon atmosphere to obtain BaNb x Ti (1-x) O 3 。
3. The method for preparing a niobium-doped cubic two-dimensional sheet strontium titanate material according to claim 2, wherein in step S1, baCO 3 、TiO 2 And Nb (Nb) 2 O 5 The molar ratio is 1: (1-x): 0.5x; the burial firing specifically comprises the following steps: the niobium doped barium titanate presintered powder is transferred into a crucible, covered by an inverted crucible, and buried around the crucible by charcoal powder.
4. The method for preparing the niobium-doped cubic two-dimensional sheet strontium titanate material according to claim 1, wherein the step S2 specifically comprises: with TiO 2 And BaNb synthesized in step S1 x Ti (1-x) O 3 Taking NaCl and KCl mixed salt as a fused salt sintering medium as raw materials; mixing the raw materials with a fused salt sintering medium, grinding, sintering, cleaning to remove fused salt, and drying to obtain sheet Ba 6 Nb x Ti （17-x） O 40 。
5. The method for preparing the niobium-doped cubic two-dimensional flaky strontium titanate material according to claim 4, wherein in the step S2, the mass ratio of NaCl to KCl in the mixed salt is 1:2; the mass ratio of the raw materials to the fused salt sintering medium is 1:2.
6. The method for preparing the niobium-doped cubic two-dimensional flaky strontium titanate material according to claim 1, wherein the step S3 isThe method specifically comprises the following steps: in BaCO 3 And the sheet-like Ba synthesized in step S2 6 Nb x Ti (17-x) O 40 Taking NaCl as a fused salt sintering medium as a raw material, and BaCO 3 Mixing with NaCl, grinding, and adding sheet Ba 6 Nb x Ti （17-x） O 40 Mixing and sintering; cleaning the sintered product to remove molten salt, and oven drying to obtain cubic photo-like BaNb x Ti (1-x) O 3 。
7. The method for preparing the niobium-doped cubic-phase two-dimensional flaky strontium titanate material according to claim 6, wherein in the step S3, the mass ratio of the raw material to the molten salt sintering medium NaCl is 1:2.
8. The method for preparing the niobium-doped cubic two-dimensional sheet strontium titanate material according to claim 1, wherein the step S4 specifically comprises: by SrCl 2 And the cubic photo-like BaNb synthesized in step S3 x Ti (1-x) O 3 Taking NaCl as a fused salt sintering medium as a raw material, and SrCl 2 Mixing with NaCl, grinding, and adding cubic photo-like BaNb x Ti (1-x) O 3 Mixing, sintering, cleaning the sintered product to remove molten salt, and drying to obtain niobium doped cubic phase two-dimensional sheet SrNb x Ti (1-x) O 3 。
9. The method for preparing the niobium-doped cubic-phase two-dimensional flaky strontium titanate material according to claim 8, wherein in the step S4, the mass ratio of the raw material to the molten salt sintering medium NaCl is 1:1.
10. Niobium-doped cubic-phase two-dimensional flaky strontium titanate material obtained by adopting the preparation method of any one of claims 1-9.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106946566A (en) * 2017-03-23 2017-07-14 西北工业大学 A kind of preparation method of sheet barium-strontium titanate powder material
CN107673403A (en) * 2017-10-26 2018-02-09 陕西科技大学 A kind of preparation method of layered titanic acid strontium

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106946566A (en) * 2017-03-23 2017-07-14 西北工业大学 A kind of preparation method of sheet barium-strontium titanate powder material
CN107673403A (en) * 2017-10-26 2018-02-09 陕西科技大学 A kind of preparation method of layered titanic acid strontium

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