CN110563457A - nitrogen ion doped zinc oxide-based piezoresistor and preparation method thereof - Google Patents

Abstract

The invention relates to a piezoresistor and a preparation technology thereof, in particular to a nitrogen ion doped zinc oxide-based piezoresistor and a preparation method thereof. The piezoresistor comprises the following components in percentage by weight: a main component, 100 parts of ZnO; 1-3 parts of a subcomponent for realizing nitrogen ion doping; 2.802-5.005 parts of a metal compound accessory component. The preparation method comprises mixing the above materials to obtain spray slurry; then spray drying and granulating; and (5) removing glue and sintering after dry pressing and forming. Compared with a comparison group of piezoresistors which are not doped with nitrogen, the piezoresistor provided by the invention has the advantages that the piezoresistor voltage gradient and the nonlinear coefficient are improved, the residual voltage ratio is reduced, and the comprehensive performance is improved.

Description

Nitrogen ion doped zinc oxide-based piezoresistor and preparation method thereof

Technical Field

The invention relates to a piezoresistor and a preparation technology thereof, in particular to a nitrogen ion doped zinc oxide-based piezoresistor and a preparation method thereof.

background

The zinc oxide voltage-sensitive ceramic material is a semiconductor electronic ceramic material, has excellent nonlinear current-voltage relation and good surge current absorption capacity, and can be made into a voltage-sensitive resistor for protecting power electronic circuits. When the surge voltage appears at the two ends of the circuit, the resistance value of the piezoresistor is rapidly reduced, and redundant current is absorbed to protect the sensitive electronic circuit.

The most used formula of the current zinc oxide voltage-sensitive ceramic material is that ZnO is taken as a main body and a small amount of Bi is added₂O₃、Sb₂O₃、Co₂O₃、MnO₂、Ni₂O₃、Cr₂O₃And the like. The donor on this basis is doped with: (1) addition of Al (NO)₃)₃，Al³⁺zn in place²⁺Donor doping is formed, the concentration of free electrons is improved, and therefore the resistivity of crystal grains is reduced; (2) addition of TiO₂，Ti⁴⁺The concentration of free electrons is increased in a donor doping mode, and meanwhile, the growth of crystal grains can be promoted, so that the voltage-sensitive voltage gradient is effectively reduced. The acceptor is doped with: (1) an alkali metal ion; (2) silver ions. The two types of acceptor doping can reduce the concentration of carriers, improve the width of a potential barrier and increase the thickness of a depletion layer of a crystal boundary, and can effectively improve the stability of the piezoresistor. However, the above acceptor doping method has disadvantages in that when doping is performed using alkali metal ions or silver ions, donor doping may be formed by substituting zinc ions and also by entering interstitial sites, and thus the concentration of the donor doping may be higher than that of the acceptor doping, thereby increasing N-type semiconductivity. The nitrogen ions and the oxygen ions have similar radiuses, so that substitutional acceptor doping is easy to form, and if the nitrogen ions are used for acceptor doping, the problem that donor doping is formed by entering interstitial sites can be effectively avoided.

Disclosure of Invention

the invention aims to overcome the defects of the prior art and provides a nitrogen ion doped zinc oxide-based piezoresistor and a preparation method thereof. The piezoresistor prepared by the invention has the characteristics of high nonlinear coefficient, high voltage gradient and low residual voltage ratio.

The nitrogen ion doped zinc oxide-based piezoresistor comprises the following components in parts by mole:

A main component, 100 parts of ZnO;

1-3 parts of a subcomponent for realizing nitrogen ion doping;

2.802-5.005 parts of a metal compound accessory component.

In a preferred embodiment, the subcomponent for realizing nitrogen ion doping is C₃N₄。

In a preferred embodiment, the subcomponent for realizing nitrogen ion doping is a third subcomponent;

the accessory ingredients of the metal compound comprise: the first sub-component is used for realizing the nonlinear characteristic of the zinc oxide piezoresistor, the second sub-component is used for improving the potential gradient of the zinc oxide piezoresistor, and the fourth sub-component is used for improving the grain conductivity of the ceramic material.

In a preferred embodiment, the first subcomponent comprises 0.5 to 1mol parts of a bismuth metal compound, a cobalt metal compound, a nickel metal compound and a manganese metal compound; the second accessory component is an antimony metal compound, and the amount of the antimony metal compound is 0.8-1 mol part; the fourth accessory ingredient is aluminum metal compound, 0.002-0.005 mol portion.

The bismuth metal compound is Bi₂O₃. The cobalt metal compound is Co₂O₃、Co₃O₄A carbonate of cobalt or an organic salt of cobalt. The nickel metal compound is Ni₂O₃. The manganese metal compound is MnO₂、Mn₃O₄or MnCO₃. The aluminum metal compound is Al₂O₃Or Al (NO)₃)₃·9H₂And (4) O solution.

The preparation method of the nitrogen ion doped zinc oxide-based piezoresistor comprises the following steps:

(1) Weighing the first accessory component, the second accessory component and the third accessory component, uniformly mixing, and performing ball milling to prepare additive slurry;

(2) adding deionized water into the main component and the fourth auxiliary component, dispersing, uniformly mixing with the additive slurry obtained in the step (1), and then adding a polyvinyl alcohol solution to prepare spray slurry; adding 0.8-1.2 g of polyvinyl alcohol solution into every 100 g of the total amount of the main component and the auxiliary component;

(3) spray drying and granulating the spray slurry obtained in the step (2) by adopting a spray drying tower;

(4) Dry-pressing the granulation powder obtained in the step (3) into a disk-shaped blank;

(5) The blank obtained in the step (4) is sintered after glue discharging to obtain a zinc oxide-based pressure-sensitive ceramic material;

(6) Preparing silver electrodes on two end faces of the ceramic obtained in the step (5), welding leading-out ends, and encapsulating and curing by using epoxy resin to prepare the piezoresistor.

compared with the prior art, the invention has the beneficial effects that: the nitrogen element doping is realized in the zinc oxide-based pressure sensitive ceramic by adopting the traditional high-temperature solid-phase synthesis process and using carbon nitride as a nitrogen source additive. The added nitrogen mainly acts on the grain boundary layer, so that the barrier height and the width of the grain boundary depletion layer are effectively improved, and the nonlinear coefficient of the piezoresistor in a low-current and large-current area is improved; in addition, the growth of zinc oxide grains is inhibited after the carbon nitride is added, so that the voltage-sensitive voltage gradient is improved by 20-60V/mm; and finally, the residual voltage of the zinc oxide piezoresistor doped with the nitrogen ions is reduced by 0.2-0.4 compared with the piezoresistor not doped with the nitrogen ions.

Detailed Description

for a better understanding of the present invention, the present invention will be described in further detail with reference to examples, but the scope of the present invention is not limited to the examples. The reagents and apparatus used in the examples are conventional products which are commercially available.

the material of the nitrogen ion doped zinc oxide-based piezoresistor mainly comprises zinc oxide, carbon nitride and metal compounds, and comprises the following components in parts by mole:

The main component, ZnO 100mol portion;

first subcomponents for realizing the nonlinear characteristics of zinc oxide piezoresistors, respectively expressed in Bi₂O₃、Co₂O₃、Ni₂O₃And MnO₂0.5-1 mol parts of a representative bismuth metal compound, a representative cobalt metal compound, a representative nickel metal compound and a representative manganese metal compound;

A second subcomponent for increasing the potential gradient of a zinc oxide varistor, of Sb₂O₃0.8 to 1mol part of a typical antimony metal compound;

A third subcomponent for realizing nitrogen ion doping, carbon nitride C₃N₄1-3 mol parts;

a fourth sub-component for increasing the electrical conductivity of the grains of the ceramic material, with Al₂O₃0.002 to 0.005mol part of a typical aluminum metal compound.

Wherein the manganese metal compound may further contain Mn₃O₄Or MnCO₃is added in the form of (1); the cobalt metal compound may also be Co₃O₄Carbonate of cobalt element or organic salt of cobalt element; the aluminum metal compound may also be Al (NO)₃)₃·9H₂The O solution is added.

The preparation method of the nitrogen ion doped zinc oxide-based piezoresistor comprises the following steps:

(1) Weighing the first accessory component, the second accessory component and the third accessory component, uniformly mixing, and performing ball milling to prepare additive slurry;

(2) Adding deionized water into the main component and the fourth auxiliary component for dispersion, uniformly mixing the main component and the fourth auxiliary component with the additive slurry obtained in the step (1), and then adding a polyvinyl alcohol solution to prepare spray slurry; adding 0.8-1.2 g of polyvinyl alcohol solution into every 100 g of the total amount of the main component and the auxiliary component;

(3) Spray drying and granulating the spray slurry obtained in the step (2) by adopting a spray drying tower;

(4) Dry-pressing the granulation powder obtained in the step (3) into a disk-shaped blank;

(5) Removing the glue from the blank obtained in the step (4), and sintering at 1100-1145 ℃ to obtain a zinc oxide-based pressure-sensitive ceramic material;

(6) preparing silver electrodes on two end faces of the ceramic obtained in the step (5), welding leading-out ends, and encapsulating and curing by using epoxy resin to prepare the piezoresistor.

The varistor and the production method thereof according to the invention will be further described below by way of example according to the different contents of the components.

Examples 1 to 6

the varistor components were mixed as shown in Table 1 to produce 7 groups of samples, including one group of control samples. The comparison sample is not added with C₃N₄General formulation (1).

Weighing a first subcomponent Bi according to the molar parts shown in Table 1₂O₃、Co₃O₄、Ni₂O₃、MnCO₃Second subcomponent Sb₂O₃And a third subcomponent C₃N₄And uniformly mixing, adding deionized water, mixing and ball-milling to prepare additive slurry. Adding ZnO as a main component into a stirring barrel, adding an ammonium salt dispersant, and mixing ZnO: deionized water 1: adding deionized water at a ratio of 0.8, dispersing, and adding desired amount of fourth subcomponent Al (NO)₃)₃·9H₂And (3) uniformly stirring the solution O to prepare main component slurry, slowly adding the additive slurry while stirring the main component slurry, and then adding the polyvinyl alcohol solution. The polyvinyl alcohol solution was added in an amount of 1.2 wt% based on the dry powder. Evenly stirring to prepare the spray slurry. And spray drying the spray slurry to obtain the granulated powder.

And (3) dry-pressing and molding the granulated powder under the pressure of 100MPa to obtain a disk-shaped blank with the diameter of 14mm and the thickness of 1.8 mm. The blank is insulated at 600 ℃ for two hours, and then sintered at 1100 ℃ for two and a half hours to obtain a black ceramic body with the diameter of about 12 mm. Printing silver electrode slurry on two end faces of the ceramic body through a screen printing process, reducing at 550 ℃ to obtain a metal silver electrode layer, welding tinned copper wires on the two electrodes, and encapsulating and curing the sample by using epoxy resin to prepare an electrical property test sample.

Table 2 shows the results of the electrical property tests of the comparative sample and examples 1 to 6.

the first subcomponent listed in table 1 is a basic additive component for realizing the nonlinear characteristic of the zinc oxide varistor, and too small amount of the first subcomponent is not favorable for improving the nonlinear coefficient, and too much amount of the first subcomponent causes excessive grain boundary segregation phase, which affects the impulse characteristic of the varistor. The first subcomponent content in example 4 was the largest, with the highest nonlinear coefficient and the lowest varistor potential gradient; the remaining comparative samples were identical in content to the first subcomponent in the examples.

The second subcomponent listed in Table 1 is an additive component for increasing the potential gradient of a zinc oxide varistor, and antimony oxide may form a spinel phase (Zn) with zinc oxide₇Sb₂O₁₂) The spinel phase has the function of inhibiting the growth of crystal grains. The total amount of the second subcomponent is minimized in example 5, and the voltage-sensitive potential gradient is reduced as compared with example; the remaining comparative samples correspond to the second subcomponent content of the examples.

The third subcomponent shown in Table 1 is an effective additive component for realizing nitrogen ion doping, and as can be seen from comparison of examples 1 to 3 with a comparative sample (without the third subcomponent), both the varistor potential gradient and the nonlinear coefficient increase with the increase of the content of the third subcomponent.

the fourth subcomponent in Table 1 is used to improve the grain conductivity of the ceramic material, but if it is added too much, it will cause an increase in leakage current (see example 6).

As can be seen from the test data listed in Table 2, the optimal examples 1 to 3 significantly exhibit the effect of adding the third subcomponent, and have excellent low current characteristics, a varistor potential gradient of 230 to 280V/mm, a leakage current of less than 3 microamperes, and a nonlinear coefficient of more than 50.

Examples 7 to 9

The chemical composition of examples 7, 8 and 9 was the same as that of examples 1, 2 and 3, respectively, and the difference from examples 1 to 3 was that the firing temperatures were 1120 ℃, 1130 ℃ and 1145 ℃, respectively, the varistor gradient in examples 7, 8 and 9 was reduced to approximately the same level as that of the comparative sample by increasing the firing temperature, and the pulse impact test was performed, and the electrical property test results thereof are shown in table 3 (the ratio of residual voltage to varistor voltage when the varistor passed 8/20 μ s wave having a peak value of 1000A). It can be seen that the residual pressure ratios of examples 7 to 9 are all reduced compared to the comparative sample.

in conclusion, compared with the piezoresistors of the comparison group which is not doped with nitrogen, the nitrogen-doped zinc oxide-based piezoresistor prepared by the method improves the piezovoltage gradient and the nonlinear coefficient, reduces the residual voltage ratio and improves the comprehensive performance.

TABLE 1

TABLE 2

TABLE 3

As described above, the present invention can be preferably realized.

Claims (10)

1. The nitrogen ion doped zinc oxide-based piezoresistor is characterized by comprising the following components in parts by mole:

A main component, 100 parts of ZnO;

1-3 parts of a subcomponent for realizing nitrogen ion doping;

2.802-5.005 parts of a metal compound accessory component.

2. A zinc oxide based varistor according to claim 1, characterized in that the subcomponent enabling the doping of nitrogen ions is C₃N₄。

3. A zinc oxide based varistor according to claim 1, characterized in that the sub-component effecting the nitrogen ion doping is a third sub-component;

the accessory ingredients of the metal compound comprise: the first sub-component is used for realizing the nonlinear characteristic of the zinc oxide piezoresistor, the second sub-component is used for improving the potential gradient of the zinc oxide piezoresistor, and the fourth sub-component is used for improving the grain conductivity of the ceramic material.

4. The zinc oxide-based varistor according to claim 3, wherein the first subcomponent comprises 0.5 to 1mol parts of a bismuth metal compound, a cobalt metal compound, a nickel metal compound, and a manganese metal compound; the second accessory component is an antimony metal compound, and the amount of the antimony metal compound is 0.8-1 mol part; the fourth accessory ingredient is aluminum metal compound, 0.002-0.005 mol portion.

5. A zinc oxide based varistor according to claim 4, characterized in that the bismuth metal compound is Bi₂O₃。

6. a zinc oxide based varistor according to claim 4, characterized in that the cobalt metal compound is Co₂O₃、Co₃O₄A carbonate of cobalt or an organic salt of cobalt.

7. A zinc oxide based varistor according to claim 4, characterized in that the nickel metal compound is Ni₂O₃。

8. A zinc oxide based varistor according to claim 4, characterized in that the manganese metal compound is MnO₂、Mn₃O₄Or MnCO₃。

9. A zinc oxide-based varistor according to claim 4, characterized in that the aluminium metal compound is Al₂O₃Or Al (NO)₃)₃·9H₂And (4) O solution.

10. A method for the preparation of a nitrogen ion doped zinc oxide based varistor according to any of claims 3 to 6, characterized in that it comprises the following steps:

(1) Weighing the first accessory component, the second accessory component and the third accessory component, uniformly mixing, and performing ball milling to prepare additive slurry;

(2) Adding deionized water into the main component and the fourth auxiliary component, dispersing, uniformly mixing with the additive slurry obtained in the step (1), and then adding a polyvinyl alcohol solution to prepare spray slurry; adding 0.8-1.2 g of polyvinyl alcohol solution into every 100 g of the total amount of the main component and the auxiliary component;

(3) spray drying and granulating the spray slurry obtained in the step (2) by adopting a spray drying tower;

(4) Dry-pressing the granulation powder obtained in the step (3) into a disk-shaped blank;

(5) the blank obtained in the step (4) is sintered after glue discharging to obtain a zinc oxide-based pressure-sensitive ceramic material;

(6) preparing silver electrodes on two end faces of the ceramic obtained in the step (5), welding leading-out ends, and encapsulating and curing by using epoxy resin to prepare the piezoresistor.