CN107540402B - Preparation method of porous copper calcium titanate film - Google Patents

Abstract

The invention discloses porous calcium copper titanate CaCu₃Ti₄O₁₂A CCTO film is prepared from LaNiO₃The (LNO for short) is used as a buffer layer, and a CCTO wet film is coated on a substrate covered by the LNO by adopting a solution chemical method; and (4) obtaining the CCTO film with a porous structure through heat treatment. The invention does not need a template, can prepare the CCTO film material with the surface appearance presenting a porous structure under the process condition of lower cost, and has wide application prospect in the fields of porous ceramics, high-density energy storage and the like.

Description

A kind of preparation method of porous copper calcium titanate film

technical field

The invention belongs to the technical field of preparation of inorganic non-metallic materials, in particular to a preparation method of a calcium copper titanate thin film material, which refers to a method for preparing porous calcium copper titanate thin films on various substrates by a solution chemical method.

technical background

The development of porous ceramics began in the 1870s, initially only as a material for bacterial filtration and uranium purification. With the continuous improvement of the level of material preparation and the diversification of processes, various new materials and high-performance porous ceramic materials continue to emerge, and their application fields and scopes are also expanding and developing. Due to the bonding of covalent bonds and complex ionic bonds and the complex crystal structure of porous ceramics, it has the characteristics of high temperature resistance, corrosion resistance and thermal stability. Moreover, when the fluid flows through the pores, various physicochemical effects (such as capillary siphon effect, etc.) will occur on the inner and outer surfaces of the porous ceramic material. Porous ceramics have attracted great attention in the world of materials due to their many excellent properties such as low density, high permeability, large specific surface area, corrosion resistance, low thermal conductivity, and high temperature resistance. This material is widely used in catalyst carrier, industrial sewage treatment, molten metal filtration, automobile exhaust gas treatment, thermal insulation and sound insulation materials and many other aspects. With the development of science and technology, the application of porous ceramics has expanded to the field of electronics, environmental protection, biochemistry, medical materials and aviation.

With the rapid development of the information technology industry and electronics and power-related industries, electronic ceramic materials with high dielectric constant and low dielectric loss have become the focus of the industry. This type of material is mainly used in the production of high-power capacitors, so it is required to have the characteristics of light weight, high energy storage density and strong stability, which requires the material to have the characteristics of low density and large dielectric constant. Around 2000, scientists discovered CaCu ₃ Ti ₄ O ₁₂ (referred to as CCTO) material, which has a very high dielectric constant, low loss and high thermal stability, which has attracted widespread attention. Its good comprehensive properties make it expected to be used in electronic ceramic components such as high-density energy storage and high-dielectric capacitors. At present, the preparation of CCTO ceramic materials reported in the literature mostly adopts the solid-phase reaction method. The solid-phase reaction method has a large energy waste, which is not in line with the strategic trend of national sustainable development. The preparation of CCTO films mainly includes physical methods (pulsed laser deposition, magnetron sputtering, etc.) and chemical methods (sol-gel method, etc.). Among them, the chemical method has low cost, low annealing temperature (750°C), simple process steps and easy operation, which is a convenient and efficient method for preparing CCTO thin films.

Although CCTO has a high dielectric constant and can meet the needs of high-density energy storage, the CCTO materials prepared by the above methods are all dense polycrystalline ceramics, and the surface morphology has no obvious special structure, which cannot meet the light weight of devices/equipment. , The requirement of low density. At present, the preparation of porous films mostly adopts the method of filling with templates or organic polymer balls, and it is necessary to remove the templates and fillers by etching or sintering, which increases the complexity of the process.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems existing in the prior art, and propose a method for preparing a copper-calcium titanate thin film material with porous morphology on the surface without template or filler.

For achieving the above object, the concrete technical scheme adopted in the present invention is as follows:

a. Cover a layer of lanthanum nickelate LaNiO ₃ buffer layer on the substrate by physical or chemical methods, and the thickness of the buffer layer is 10-30 nm;

b. Configuration of calcium copper titanate precursor solution

Dissolve copper nitrate Cu(NO ₃ ) ₂ and calcium nitrate Ca(NO ₃ ) ₂ into ethylene glycol methyl ether in a molar ratio of 3:1, and heat and stir in a water bath at 30～80℃ for 1～6 hours to form a homogeneous solution; then measure butyl titanate and the same moles of acetylacetone according to the ratio of Ca:Ti atomic molar ratio of 1:4, add the solution, stir and heat in a water bath at 30 to 80 ° C for 1 to 8 hours , to form a homogeneous solution, and finally prepare a calcium copper titanate precursor solution with a concentration of 0.01 to 0.1 mol/L;

c. Preparation of porous calcium copper titanate film

The copper calcium titanate precursor solution is coated on the substrate with the lanthanum nickelate buffer layer by means of spin coating or pulling coating to obtain a copper calcium titanate wet film; three stages are carried out in a rapid annealing furnace Type heat treatment: the first stage, the temperature is 140～200℃, the duration is 180～360 seconds; the second stage, the temperature is 360～420℃, the duration is 180～360 seconds; The porous calcium copper titanate film is layered, and the coating-heat treatment process is repeated to obtain a multilayer copper calcium titanate porous film;

Compared with the prior art, the present invention is characterized in that: (1) the obtained calcium copper titanate film has a porous structure; (2) no template or filler is required during the growth process of the calcium copper titanate film; (3) porous The pore size of calcium copper titanate films can be adjusted.

Description of drawings

Fig. 1 is the AFM image of the surface of the lanthanum nickelate buffer layer of embodiment 1;

2 is an AFM image of the porous calcium copper titanate film of Example 1;

Fig. 3 is the height scale diagram of the AFM diagram shown in Fig. 1;

FIG. 4 is a cross-sectional graph of the porous calcium copper titanate thin film of Example 1. FIG.

Detailed ways

Example 1

a. Substrate selection and cleaning

A <100> heavily doped silicon substrate was used, the substrate was ultrasonically treated with ethanol and deionized water for 20 minutes, and then placed in a rapid heat treatment device for two-stage annealing: the first stage, the temperature was 200 °C for 200s; the second stage, the temperature 400℃ for 200s.

b. Preparation of lanthanum nickelate buffer layer

Weigh 3.2 grams of lanthanum nitrate La(NO ₃ ) ₃ .6H ₂ O solid, and weigh nickel acetate C ₄ H ₆ O ₄ Ni 4H ₂ O solid according to the ratio of La:Ni atomic molar ratio of 1:1, add ethanol solvent , stirred and heated in a 40° C. water bath for about 3 hours to obtain a homogeneous solution of lanthanum nickelate with a concentration of 0.1 mol/L. Let it stand for a while, and it can be used without precipitation.

The cleaned silicon substrate was placed in a glue homogenizer, the rotational speed was set at 4000 rpm, and the above-mentioned lanthanum nickelate solution was used to coat a layer of lanthanum nickelate wet film on the silicon substrate; put into a rapid heat treatment device for three stages. Heat treatment: the first stage, the temperature is 180°C for 240 seconds; the second stage, the temperature is 380°C for 240 seconds; the third stage, the temperature is 700°C for 300 seconds, a layer of lanthanum nickelate buffer with a thickness of about 10 nanometers can be grown Floor. It can be seen from Fig. 1 that the surface of lanthanum nickelate is smooth, and there are no obvious holes.

c. Configuration of calcium copper titanate precursor solution

Weigh copper nitrate Cu(NO ₃ ) ₂ and calcium nitrate Ca(NO ₃ ) ₂ solids 0.3542 g and 1.0872 g respectively, dissolve them in ethylene glycol methyl ether solvent, heat and stir them in a water bath at 40°C for about 1 hour to make them uniform. quality solution. Then add 0.9 ml of butyl titanate and acetylacetone into the solution, stir and heat in a 40°C water bath for about 2 hours to form a homogeneous solution, and finally prepare a calcium copper titanate solution with a concentration of 0.05mol/L.

d. Preparation of porous calcium copper titanate film

The silicon wafer with the lanthanum nickelate buffer layer was placed on the glue spinner, the speed was set to 4000r/min, the time was 20 seconds, and the calcium copper titanate solution was coated to obtain a calcium copper titanate wet film. A three-stage heat treatment is performed in a rapid annealing furnace: the first stage, the temperature is 180 °C for 240 seconds; the second stage, the temperature is 380 °C for 240 seconds; the third stage, the temperature is 700 °C for 300 seconds, to obtain a layer of copper titanate For the calcium porous film, repeat the above coating-heat treatment process to obtain a two-layer calcium copper titanate porous film (see Figure 2) with a thickness of about 40 nanometers and a maximum pore size of about 120 nanometers (see Figure 4).

Example 2

a. Substrate selection and cleaning

Quartz glass was used as the substrate. The substrates were sonicated with ethanol and deionized water for 20 min, and blown dry with high-purity nitrogen.

b. Preparation of lanthanum nickelate buffer layer

Fix the cleaned quartz glass substrate on the sample tray of the pulsed laser deposition system. The deposition chamber was evacuated to below 10 ^-5 Pa; oxygen with a purity of not less than 99.999% was introduced, and the pressure of the chamber was maintained at 5 Pa; the sample tray was heated to 700 ^o C; the lanthanum nickelate target was ablated by pulsed laser, and the laser frequency was 5Hz ; After the laser is turned off, the oxygen pressure in the cavity is increased to 100Pa, and the temperature is kept for 30 minutes to obtain a lanthanum nickelate buffer layer with a thickness of about 10 nanometers.

c. Configuration of calcium copper titanate precursor solution

Calcium nitrate Ca(NO ₃ ) ₂ and copper nitrate Cu(NO ₃ ) ₂ were dissolved in ethylene glycol methyl ether at a Ca:Cu atomic molar ratio of 1:3, and heated and stirred to form a homogeneous solution. Then measure butyl titanate and an equal amount of acetylacetone according to the Ca:Ti atomic molar ratio of 1:4 and add it to the solution, stir and heat it in a water bath at 40°C for about 2 hours to form a homogeneous solution, and finally make up to a concentration of 0.05mol /L of calcium copper titanate precursor solution.

d. Preparation of porous calcium copper titanate film

The substrate with the lanthanum nickelate buffer layer was placed on the glue-spraying machine, the rotation speed was set at 6000 r/min, the glue-spreading time was 20 seconds, and the calcium copper titanate solution was coated to obtain a calcium copper titanate wet film. A three-stage heat treatment is performed in a rapid annealing furnace: the first stage, the temperature is 180 °C for 240 seconds; the second stage, the temperature is 380 °C for 240 seconds; the third stage, the temperature is 750 °C for 300 seconds, a layer of copper titanate is obtained For the calcium porous film, the above coating-heat treatment process is repeated to obtain a multilayer copper calcium titanate porous film.

Claims (1)

1. The preparation method of the porous calcium copper titanate film is characterized by comprising the following specific steps of:

a. covering a layer of LaNiO on the substrate by a physical or chemical method₃A buffer layer having a thickness of 10 to 30 nm;

b. preparation of calcium copper titanate precursor solution

Taking copper nitrate Cu (NO)₃)₂Ca (NO), Ca nitrate₃)₂Dissolving the solid into ethylene glycol monomethyl ether according to the mol ratio of 3:1, heating and stirring in a water bath at the temperature of 30-80 ℃ for 1-6 hours to form a homogeneous solution; weighing butyl titanate and acetylacetone with the same mole number into the solution according to the molar ratio of Ca to Ti atoms of 1 to 4, stirring and heating the solution in a water bath at the temperature of 30-80 ℃ for 1-8 hours to form a homogeneous solution, and finally preparing a calcium copper titanate precursor solution with the concentration of 0.01-0.1 mol/L;

c. preparation of porous copper calcium titanate film

Coating a calcium copper titanate precursor solution on a substrate with a lanthanum nickelate buffer layer by adopting a rotary coating or pulling coating mode to obtain a wet calcium copper titanate film; carrying out three-stage heat treatment in a rapid annealing furnace: in the first stage, the temperature is 140-200 ℃ and the time is 180-360 seconds; in the second stage, the temperature is 360-420 ℃ and the time is 180-360 seconds; in the third stage, the temperature is 650-850 ℃ for 180-600 seconds to obtain a layer of porous calcium copper titanate film, and the coating-heat treatment process is repeated to obtain a plurality of layers of porous calcium copper titanate films; the pore diameter is in the range of 40-200 nm.

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