News

Magnesium-containing ternary NTC thermistor material

2019-09-27  625

Negative temperature coefficient of magnesium-containing quaternary system

The thermistor material is prepared by using an oxide solid phase method to prepare a powder material by using an oxide of manganese, cobalt, nickel and magnesium as a raw material, and the powder is prepared by drying, calcining, pre-compressing and sintering. After the obtained thermistor material is continuously aged at a temperature of 150 ° C for 500 h, the resistance change rate is only 1% -4%, and the electrical parameter is B25/50 = 3630-3720K ± 0.5%, ρ 25 °C = 1270-3522 Ω. Cm ± 3%, confirming the stability and reliability of the material. The resistor material has the characteristics of high B low resistance, good stability and high precision, and is suitable for suppressing surge current and temperature measurement, control and line compensation of refrigerators and air conditioners.

The negative temperature coefficient (NTC) thermistor has high sensitivity and micro characteristics. It is in great demand in many home appliances and information industries. However, the parameters of traditional thermistors can no longer meet the current market demand, and the development has a high B value. A thermistor with low resistance, good stability and high precision for suppressing inrush current has a good market prospect. Conventional NTC thermistor ceramic materials generally consist of oxides of excessive metals such as manganese, cobalt, nickel, etc. These heat sensitive materials have high B value, high resistivity, low B value, and low resistivity, which is difficult to obtain. A resistor with a high B value and low resistance (B ≥ 3600K, R ≤ 1000Ω). In order to produce NTC thermistor elements with high B value, low resistance and good stability for suppressing inrush current, the key is to improve the composition and ratio of the material system.

The invention aims at the background of the high-B low-resistance, high-stability and high-precision NTC components, and based on the demand for the B-value, resistance and reliability of the thermistor material, the raw material system, the formulation, The preparation method and sintering process were designed and optimized. Firstly, the material system and formulation were studied. The appropriate amount of MgO was added to the traditional MnCoNiO ternary system to form MnNiCoMgO quaternary material, which made the parameters and stability of the components. The requirements for the properties and precision are met; in addition, a large number of tests are carried out on the preparation method and the sintering process of the powder material to optimize the powder, and the heat-sensitive material powder is prepared by the second wet ball milling method, and the obtained powder is fine and uniform; Thermistors made of resistor-like materials have high yield, good interchangeability, good stability and high reliability.

Summary of the invention

[0004] The object of the present invention is to develop a magnesium-containing quaternary negative temperature coefficient thermistor material with high B, low resistance, good stability and high precision, which is oxidized by manganese, cobalt, nickel and magnesium. The material is used as a raw material, and the powder material is prepared by an oxide solid phase method. The powder is dried, calcined, pre-compressed, sintered, and coated with an electrode to form a disk of Φ10 mm×1.5 mm. The resistor material has the characteristics of high B low resistance, good stability and high precision, and is suitable for suppressing surge current and temperature measurement, control and line compensation of refrigerators and air conditioners.

[0005] A magnesium-containing quaternary negative temperature coefficient thermistor material according to the present invention, the resistive material is an oxide of manganese, cobalt, nickel, magnesium as a raw material, and the ratio of each component is atomic percentage : manganese 41.67%, nickel 25%, cobalt 23.33% -30%, magnesium 3.33% -10%.

[0006] The preparation method of the magnesium-containing quaternary negative temperature coefficient thermistor material is carried out according to the following steps:

[0007] a, the atomic percentage of manganese, cobalt, nickel, magnesium oxide powder was placed in a planetary ball mill, using deionized water as a dispersion medium, ball milling, time 8h;

[0008] b, the slurry in step a is washed, dried at a temperature of 90 ° C for 24 h, and then manually milled and dispersed, the obtained powder was calcined at a temperature of 950 ° C for 2 h;

[0009] c, after the calcination in step b, the powder is deionized water as a dispersion medium, and again ball milled in a planetary ball mill, time 12h;

[0010] d, the slurry in step c is washed, dried at a temperature of 90 ° C for 24 h, and then hand-grinding dispersion, to obtain a negative temperature coefficient thermistor powder material;

[0011] e, the powder material obtained in step d is compacted at a pressure of 30-40Kg / cm2, the time is 1-10min, the formed bulk material is cold isostatic pressing, the pressure is 300-400MPa The pressure is maintained for 1-10 min, and then sintered at a temperature of 1150-1250 ° C for 2-3 h to obtain a negative temperature coefficient thermistor material;

[0012] Step a and step c The weight ratio of each substance in the ball mill tank is: ball: water = 1 : 2.5 : 1.

[0013] The average particle size of the powder material of step d is 1.374 to 1.648 μm.

[0014] f,

[0015] The magnesium-containing quaternary negative temperature coefficient thermistor material according to the present invention, the main raw materials of the resistive material are MnO2, Co2O3, Ni2O3, MgO, and an appropriate amount of MgO can form well with MnO2, Co2O3, Ni2O3. A solid solution of spinel structure, the ionic radius of Mg2+ is about 0.078 nm, which tends to occupy the tetrahedral void of the spinel structure, increasing the carrier concentration of the conductive system in the material system, which helps to reduce the resistivity of the material. At the same time, it can combine the stability of traditional manganese, cobalt and nickel ternary materials; the thermistor powder is prepared by the oxide solid phase method, which can be industrially mass-produced, and the secondary wet ball milling process is used to control the material. , the weight ratio of the ball, the water and the milling time can obtain a fine and uniform precursor powder, which is then dried and calcined, and finally a uniformly dispersed manganese, cobalt, nickel and magnesium mixed oxide powder is obtained; the powder compact is pressed After forming, isostatic pressing and sintering, a negative temperature coefficient thermistor material is prepared, and then the prepared thermistor material is coated with a silver electrode on both sides, and a tinned copper wire is used as a lead to obtain Φ10 mm×1. .5mm wafer material, the resistance coefficient change rate of the obtained thermistor material after continuous aging for 500h at 150 °C is only 1% -4%, and the electrical parameter is B25/50 =3630-3720K±0.5%, ρ25 °C = 1270-3522 Ω · cm ± 3%, confirming the stability and reliability of the material. The material has high B low resistance, good consistency, high stability, high precision and repeatability. It is suitable for suppressing inrush current and temperature measurement, control and line compensation of refrigerators and air conditioners.

[0016] The magnesium-containing quaternary negative temperature coefficient thermistor material of the present invention has the following characteristics:

[0017] In the conventional MnCoNiO ternary system NTC thermistor ceramic material, an appropriate amount of MgO is added, and MgO can form a good spinel structure solid solution with MnO2, Co2O3, Ni2O3, and Mg ions tend to occupy the spinel structure. The tetrahedral voids can inhibit the precipitation of NiO in the second phase, resulting in a single-phase spinel structure, increasing the carrier concentration of the conductive system in the material system, helping to reduce the resistivity of the material while at the same time being able to combine the traditional The stability of the MnCoNiO ternary system material makes the material system have a high B value, and a low resistance value and good stability.

[0018] The invention adopts a secondary wet ball milling method to prepare a heat-sensitive material powder, and the obtained powder is fine and uniform, and the average particle size is 1.374-1.648 μm, so that the thermistor material has good consistency and stability. Sexuality and repeatability to ensure the accuracy of the thermistor.

 detailed description

[0019] Embodiment 1

[0020] a, according to the atomic percentage, weigh MnO241.67%, Co2O323.33%, Ni2O325%, MgO 10% powder placed in a planetary ball mill, using deionized water as a dispersion medium, ball milling, time 8h, The weight ratio of each substance in the ball mill tank is: ball: water = 1 : 2.5 : 1 ;

[0021] b, the slurry in step a is washed, dried at a temperature of 90 ° C for 24 h, and then manually milled and dispersed, the obtained powder was calcined at a temperature of 950 ° C for 2 h;

[0022] c, after calcination in step b, the powder is deionized water as a dispersion medium, and again ball milled in a planetary ball mill, time 12h, the weight ratio of each substance in the ball mill tank is: ball: water = 1 : 2.5: 1

[0023] d, the slurry in step c is washed, dried at a temperature of 90 ° C for 24 h, and then hand-grinding dispersion, to obtain a negative temperature coefficient thermistor powder material, the average particle size of 1.374-1.498 μm;

[0024] e, the powder material obtained in step d is compacted at a pressure of 30Kg / cm2 for 1min, the formed bulk material is subjected to cold isostatic pressing, and the pressure is maintained at 300MPa for 1min, then After sintering at a temperature of 1150 ° C for 2 h, a negative temperature coefficient thermistor material can be obtained;

[0025] The ceramic block material sintered in the step e is coated on both the front and the back with a silver-plated electrode, and the tinned copper wire is used as a lead to obtain a wafer having a size of Φ10 mm×1.5 mm. The obtained thermistor wafer material was aged at a temperature of 150 ° C for 500 h, and the resistance change rate was 1.48%, and the electrical parameter was B25/50 = 3663 K ± 0.5%, and ρ 25 ° C = 1270 Ω · cm ± 3%.

[0026] It is suitable for suppressing surge current and temperature measurement, control, and line compensation of refrigerators, air conditioners, and the like.

Embodiment 2

[0028] a, according to the atomic percentage, weigh MnO241.67%, Co2O330%, Ni2O325%, MgO 3.33% in the planetary ball mill, using deionized water as the dispersion medium, ball milling, time 8h, each in the ball mill tank The weight ratio of the material is: ball: water = 1 : 2.5 : 1 ;

[0029] b, the slurry in step a is washed, dried at a temperature of 90 ° C for 24 h, and then manually milled and dispersed, the obtained powder was calcined at a temperature of 950 ° C for 2 h;

[0030] c, after calcination in step b, the powder is deionized water as a dispersion medium, and ball milled again in a planetary ball mill for 12 h, the weight ratio of each substance in the ball mill tank is: ball: water = 1 : 2.5: 1 ;

[0031] d, the slurry in step c is washed, dried at a temperature of 90 ° C for 24 h, and then hand-grinding dispersion, to obtain a negative temperature coefficient thermistor powder material, the average particle size of 1.014-1.608μm;

[0032] e, the powder material obtained in step d is compacted at a pressure of 40 Kg / cm 2 for 10 min, the formed bulk material is subjected to cold isostatic pressing, and the pressure is maintained at 400 MPa for 10 min, then After sintering at a temperature of 1250 ° C for 3 h, a negative temperature coefficient thermistor material can be obtained;

[0033] The ceramic block material sintered in step e is coated on both sides of the ceramic block, and the tinned copper wire is used as a lead to obtain a wafer having a size of Φ10 mm×1.5 mm, and the obtained thermistor wafer material is When the temperature was aged at 150 ° C for 500 h, the resistance change rate was 1.09%, and the electrical parameters were B25/50 = 3717K ± 0.5%, and ρ25 ° C = 2818 Ω · cm ± 3%.

[0034] It is suitable for suppressing inrush current and temperature measurement, control, and line compensation of refrigerators, air conditioners, and the like.

[0035] Example 3

[0036] a, according to the atomic percentage, weigh MnO241.67%, Co2O326.33%, Ni2O325%, MgO 7% placed in a planetary ball mill, using deionized water as a dispersion medium, ball milling, time 8h, ball mill The weight ratio of each substance in the material is: ball: water = 1 : 2.5 : 1 ;

[0037] b, the slurry in step a is washed, dried at a temperature of 90 ° C for 24h, and then manually milled and dispersed, the obtained powder was calcined at a temperature of 950 ° C for 2h;

[0038] c after the calcination in step b powder using deionized water as a dispersion medium, ball milling in a planetary ball mill again, time 12h, the weight ratio of each material in the ball mill tank is: ball: water = 1 : 2.5: 1 ;

[0039] d, the slurry in step c is washed, dried at a temperature of 90 ° C for 24 h, and then hand-grinding dispersion, to obtain a negative temperature coefficient thermistor powder material, the average particle size is 1.398-1.648 μm;

[0040] e, the powder material obtained in step d is compacted at a pressure of 35Kg / cm2 for 5min, the formed bulk material is subjected to cold isostatic pressing, and the pressure is maintained at 350MPa for 5min, then After sintering at a temperature of 1200 ° C for 2.5 h, a negative temperature coefficient thermistor material can be obtained;

[0041] The ceramic block material sintered in step e is coated on both sides of the ceramic block, and the tinned copper wire is used as a lead to obtain a wafer having a size of Φ10 mm×1.5 mm, and the obtained thermistor wafer material is After aging at 150 ° C for 500 h, the change rate of resistance was 3.86%, and the electrical parameters were B25/50 = 3717K ± 0.5%, ρ25 ° C = 3522 Ω · cm ± 3%.

[0042] It is suitable for suppressing surge current and temperature measurement, control and line compensation of refrigerators, air conditioners, and the like.