CN1384079A - Prepn and application of Li and Ti doped nickel oxide-base ceramic - Google Patents

Abstract

A preparation method and application of a lithium-titanium co-doped nickel oxide-based ceramic material, using a sol-gel method to prepare lithium-doped NiO precursor powder, and then mixing and sintering with _TiO2 to obtain a lithium-titanium co-doped oxide Nickel (Li-Ti-Ni-O) ceramics; the precursor powder prepared by sol-gel technology, the product particle size is small, the chemical uniformity is good, and it is easy to sinter, which is beneficial to improve the performance of the material. By adjusting the doping amount of lithium and titanium, the dielectric properties of the material can be obviously changed to meet different requirements. The system has an unusually high dielectric constant (ε>10 ⁴ , at =10～10MHz) and good temperature stability, and is a new type of lead-free giant dielectric constant material. In the field of thermoelectricity, it can be used in thermoelectric power generation (waste heat utilization) and thermoelectric refrigeration systems; in the field of dielectrics, it can be used in lasers, displays, solid state detection, etc. in addition to manufacturing high energy storage density capacitors.

Description

Preparation method and application of a lithium-titanium co-doped nickel oxide-based ceramic

technical field

The invention relates to an oxide ceramic material, in particular to a preparation method and application of a lithium-titanium co-doped nickel oxide-based ceramic material, belonging to the technical field of thermoelectric and dielectric materials.

Background technique

Palchik et al pointed out in their article (Nanostructured Materials.1999, 11(3), 415-420) that NiO is a very widely used material and can be used in the field of catalysis, fuel cell electrodes and gas sensors. Woosuck Shin et al pointed out in their article (Materials Letters.2000, 45, 302-306; Jpn.J.Appl.Phys.2000, 39(3), 145) that lithium-doped NiO or lithium-sodium co-doped Miscellaneous NiO ceramics can also be used as thermoelectric conversion materials.

The commonly used dielectric materials with high permittivity can be roughly divided into the following categories. One type is the high dielectric oxide or perovskite structure composite oxide represented by titanium and niobium mentioned in Tao Li et al.'s article (Materials Letters. 2000, 44, 1-5). Its dielectric constant value can reach hundreds, such as rutile porcelain, calcium titanate porcelain, magnesium titanate porcelain, titanium-zirconium series porcelain and titanium-magnesium-lanthanum series porcelain. The other is the sulfides, selenides, and tellurides represented by copper, silver, mercury, and thallium mentioned by Sun Rizhen in the book "Basics of Dielectric Physics" (South China University of Technology Press, 2000). The coefficient is about tens. Another class of materials is ferroelectric ceramics. Li Biaorong and others mentioned in the book "Inorganic Dielectrics" (Huazhong University of Science and Technology, 1995) that their dielectric coefficients are as high as 10 ³ to 10 ⁴ , and they are mainly barium titanate-based ceramics and lead-containing ferroelectric systems (PMN, PZN, PFW, PFN, PNN, etc.). All of the above materials have obvious disadvantages: (1) the dielectric constants of the first two types of materials are small, both less than 1000; (2) the dielectric constants of ferroelectric materials are unstable and change significantly with temperature; Ferroelectric materials with large electrical constants are generally Pb-containing materials (PZN, PFW, PFN, PNN, etc.), which cause great pollution during preparation and use, which is not conducive to environmental protection requirements.

In summary, there is no report on the application of NiO-doped ceramics in the field of dielectric materials, and it is a new type of dielectric material.

As we all know, the preparation process is the basis of material technology. Even if the composition is the same, different preparation processes will lead to great changes in the properties of materials. Doping nickel oxide is generally prepared by solid phase method (Woosuck Shin, et al. Materials Letters. 2000, 45, 302-306; Jpn. J. Appl. Phys. 2000, 39 (3), 145) at present. This traditional method takes a long time to sinter, consumes a lot of energy, and the uniformity of the obtained material is poor, resulting in a decline in performance.

Contents of the invention

The purpose of the present invention is to solve many problems existing in the synthesis of doped nickel oxide ceramics in the traditional solid-state method, to provide a lithium-titanium co-doped nickel oxide-based ceramic material and its preparation method, that is, to use the "sol-gel method" To reduce the reaction temperature and shorten the reaction time, the obtained material can not only be used in the field of thermoelectricity, but also can be used as a dielectric material.

Technical scheme of the present invention is as follows:

A lithium-titanium co-doped nickel oxide-based ceramic material is characterized in that it has the following chemical formula:

Li _A Ti _B Ni _CO

Among them: A is 0.05～0.3

B is 0.02～0.05

C should satisfy: 1-A-B

The above-mentioned lithium-titanium co-doped nickel oxide-based ceramic material can be prepared according to the following steps:

(1). Weigh Ni(NO ₃ ) ₂ , LiNO ₃ and TiO ₂ with a molar ratio of 0.93～0.65:0.05～0.3:0.02～0.05 respectively;

(2). First dissolve Ni(NO ₃ ) ₂ and LiNO _a in deionized water to form a transparent solution with a concentration of 0.5-1mol/L, and then add 1.3-2 times the inorganic salt Ni(NO ₃ ) ₂ The molar amount of citric acid is stirred at 70°C to 80°C until a transparent and viscous sol is formed;

(3). Dry the sol at 110°C to 130°C to obtain a gel, take out the dry gel, grind it, and pre-calcine at 400°C to 600°C for 1 hour to 2 hours to obtain a black Li-Ni-O precursor powder;

(4). Mix the Li-Ni-O precursor powder prepared in step (3) with the weighed TiO ₂ powder by ball milling, dry press at 4Mpa to 6Mpa, and sinter at 1100°C to 1300°C for 4 hours. After 8 hours, a bulk Li-Ti-Ni-O based ceramic material was obtained.

The lithium-titanium co-doped nickel oxide series ceramic material prepared by the invention can be used as a dielectric material.

Because the present invention adopts the solution chemical method (sol-gel method), the reaction temperature is reduced, the reaction time is shortened, and a nanoscale precursor compound with uniform chemical composition is obtained. The particle size of the precursor powder is small, and the chemical uniformity is good. The temperature is low, the time is short, and the sintering process can be carried out at a lower temperature, thereby saving energy. (Li-Ti-Ni-O)-based ceramic material obtained by co-doping nickel oxide with lithium and titanium, which has an unusually high dielectric constant (ε>10 ⁴ , at =10-10MHz) and stable temperature It is a lead-free system; changing the doping amount of lithium and titanium can obviously change the dielectric properties of the material, and can also change the spectrum of the dielectric constant of the material. The characteristics and temperature dependence make it meet different industrial use requirements (such as X7R characteristics), and it is a new type of lead-free dielectric material. The lithium-titanium co-doped nickel oxide ceramic material synthesized by the invention is widely used in engineering technology. In the field of thermoelectricity, it can be used in thermoelectric power generation (waste heat utilization) and thermoelectric refrigeration systems; in the field of dielectrics, it can be used in laser, display, solid state detection, etc. in addition to manufacturing high energy storage density capacitors.

Description of drawings

Figure 1: XRD patterns of samples with different lithium and titanium doping contents.

Figure 2: Typical powder TEM images.

Figure 3: SEM image of Li _0.05 Ti _0.02 Ni _0.93 O sample.

Figure 4: SEM image of Li _0.1 Ti _0.02 Ni _0.88 O sample.

Figure 5: SEM image of Li _0.2 Ti _0.04 Ni _0.76 O sample.

Figure 6: SEM image of Li _0.3 Ti _0.02 Ni _0.68 O sample.

Figure 7: SEM image of Li _0.1 Ti _0.05 Ni _0.85 O sample.

Figure 8: Relative permittivity as a function of frequency at different temperatures (Li _0.1 Ti _0.05 Ni _0.85 O).

Figure 9: Relative permittivity as a function of temperature at a fixed frequency (Li _0.1 Ti _0.05 Ni _0.85 O).

Figure 10: Relative permittivity as a function of temperature at a fixed frequency (Li _0.05 Ti _0.02 Ni _0.93 O).

Figure 11: Relative permittivity as a function of frequency at different temperatures (Li _0.05 Ti _0.02 Ni _0.93 O).

Figure 12: Relative permittivity as a function of frequency at room temperature (Li _0.1 Ti _0.02 Ni _0.88 O).

Figure 13: Relative permittivity as a function of frequency at room temperature (Li _0.2 Ti _0.04 Ni _0.76 O).

Figure 14: Relative permittivity as a function of frequency at room temperature (Li _0.3 Ti _0.02 Ni _0.68 O).

Figure 15: Effect of the doping amount of lithium (left, Ti content 0.02) and titanium (right, Li content 0.1) on the dielectric constant of the material.

Detailed ways

All chemicals were commercially available and of analytical grade without further purification.

Example 1

Ni(NO ₃ ) ₂ (0.093mol) and LiNO ₃ (0.005mol) were dissolved in 250ml of deionized water and stirred to obtain a transparent solution. Dissolve 0.121mol of citric acid in the above solution and stirred at 70°C for about 3 hours to obtain a viscous sol , put the sol in an oven, dry at 110°C for about 12 hours to obtain a xerogel, grind it, and pre-calcine at 400°C for 2 hours to obtain a black Li-Ni-O precursor powder. The powder was mixed with TiO ₂ (0.002mol) powder, ball milled, dried, dry-pressed at 4Mpa, and sintered at 1300°C for 4 hours to obtain a bulk Li _0.05 Ti _0.02 Ni _0.93 O ceramic material. At room temperature, the relative permittivity ε = 12190 (10000Hz). The characterization and performance of the material are shown in Figure 1, Figure 3, Figure 10 and Figure 11; the precursor is a spherical particle with a size of about 30 nanometers (see Figure 2).

Example 2

Ni(NO ₃ ) ₂ (0.088mol) and LiNO ₃ (0.01mol) were dissolved in 250ml of deionized water, stirred to obtain a transparent solution, 0.176mol of citric acid was dissolved in the above solution, and stirred at 80°C for about 3 hours to obtain a viscous sol , put the sol in an oven, dry at 130°C for about 12 hours to obtain dry gel, grind it, and pre-calcine at 600°C for 1 hour to obtain black Li-Ni-O precursor powder. The powder was mixed with TiO ₂ (0.002mol) powder, ball milled, dried, dry-pressed at 5 MPa, and sintered at about 1100°C for 8 hours to obtain a bulk Li _0.1 Ti _0.02 Ni _0.88 O ceramic material. At room temperature, the relative permittivity ε = 52280 (10000Hz). The characterization and properties of the materials are shown in Figure 1, Figure 4 and Figure 12.

Example 3

Dissolve Ni(NO ₃ ) ₂ (0.076mol) and LiNO ₃ (0.02mol) in 250ml of deionized water and stir to obtain a transparent solution. Dissolve 0.128mol of citric acid in the above solution and stir at 70°C for about 3 hours to obtain a viscous sol , Put the sol in an oven, dry at 120°C for about 12 hours to obtain a dry gel, grind it, and pre-calcine at 450°C for 1 hour to obtain a black precursor powder. The powder was mixed with TiO ₂ (0.004mol) powder, ball milled, dried, dry-pressed at 5 MPa, and sintered at about 1280°C for 6 hours to obtain a bulk Li _0.2 Ti _0.04 Ni _0.76 O ceramic material. At room temperature, relative permittivity ε = 200850 (10000Hz). The characterization and properties of the materials are shown in Figure 1, Figure 5 and Figure 13.

Example 4

Ni(NO ₃ ) ₂ (0.068mol) and LiNO ₃ (0.03mol) were dissolved in 250ml of deionized water, stirred to obtain a transparent solution, 0.126mol of citric acid was dissolved in the above solution, and stirred at 60°C for about 3 hours to obtain a viscous sol , put the sol in an oven, dry at 110°C for about 12 hours to obtain dry gel, grind it, and pre-calcine at 450°C for 1 hour to obtain black LiNiO precursor powder. Mix LiNiO powder and TiO ₂ (0.002mol) powder, ball mill, dry, dry press at 4MPa, and sinter at 1280°C for 4 hours to obtain a bulk Li _0.3 Ti _0.02 Ni _0.68 O ceramic material. At room temperature, the relative permittivity ε = 559800 (10000Hz). The characterization and properties of the materials are shown in Figure 1, Figure 6 and Figure 14.

Example 5

Ni(NO ₃ ) ₂ (0.085mol) and LiNO ₃ (0.01mol) were dissolved in 250ml of deionized water and stirred to obtain a transparent solution. Dissolve 0.130mol of citric acid in the above solution and stirred at 70°C for about 3 hours to obtain a viscous sol , put the sol in an oven, dry at 120°C for about 12 hours to obtain dry gel, grind it, and pre-calcine at 500°C for 1 hour to obtain black LiNiO precursor powder. Mix LiNiO powder and TiO ₂ (0.005mol) powder, ball mill, dry, dry press at 5Mpa, and sinter at 1280°C for 8 hours to obtain bulk Li _0.1 Ti _0.05 Ni _0.85 O ceramic material. At room temperature, the relative permittivity ε = 9329 (10000Hz). The characterization and properties of the materials are shown in Figure 1, Figure 7, Figure 8 and Figure 9.

The effect of the doping amount of lithium and titanium on the dielectric constant of the material is shown in Figure 15.

Claims (3)

1. Li and Ti doped nickel oxide-base ceramic material is characterized in that having following chemical formula:

Li _ATi _BNi _CO

Wherein: A is 0.05～0.3

B is 0.02～0.05

C should satisfy: 1-A-B

2. prepare the method for Li and Ti doped according to claim 1 nickel oxide-base ceramic material, this method is carried out as follows:

(1) weighing is 0.93～0.65: 0.05～0.3: 0.02～0.05 Ni (NO in molar ratio respectively ₃) ₂, LiNO ₃And TiO ₂

(2) earlier with Ni (NO ₃) ₂And LiNO ₃Be dissolved in the deionized water, forming concentration is the clear solution of 0.5～1mol/L, adds 1.3～2 times again to adding inorganic salt Ni (NO ₃) ₂The citric acid of molar weight is 70 ℃～80 ℃ stirrings, till forming transparent heavy-gravity colloidal sol;

(3) colloidal sol is made gel in 110 ℃～130 ℃ following dryings, take out xerogel, grind,, obtain presoma black Li-Ni-O powder 400 ℃～600 ℃ pre-burnings 1 hour～2 hours;

(4) with the presoma Li-Ni-O powder that makes in the step (3) and the TiO of weighing ₂The powder ball milling mixes, and is dry-pressing formed under 4Mpa～6Mpa, and 1100 ℃～1300 ℃ sintering 4 hours～8 hours obtain block Li-Ti-Ni-O stupalith.

3. a kind of Li and Ti doped nickel oxide-base ceramic material as claimed in claim 1 is characterized in that using as dielectric substance.

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