CN103030406A

CN103030406A - Ptc ceramic sintering method

Info

Publication number: CN103030406A
Application number: CN2013100003734A
Authority: CN
Inventors: 刘来君; 郑少英; 方亮; 黄延民; 史丹平
Original assignee: Guilin University of Technology
Current assignee: Guilin University of Technology
Priority date: 2013-01-02
Filing date: 2013-01-02
Publication date: 2013-04-10

Abstract

The invention discloses a PTC (positive temperature coefficient) ceramic sintering method. The method comprises the steps that a PTC ceramic biscuit is put into a crucible, and subjected to quick temperature rise-heat preservation, quick cooling-heat preservation, and further quick temperature rise to slightly high temperature-heat preservation; after the three-step sintering technology, a sintering block body is compacted quickly, and then subjected to furnace cooling; and the density of ceramic reaches the theoretical density. The sintering block body experiences higher sintering temperature, and then is subjected to the heat preservation at a lower temperature by changing the ceramic sintering technology; quick moving of a crystal boundary is inhibited; the sintering block body with fine and uniform crystal grains can be obtained, and further treated at the slightly high temperature; the sintering time can be shortened greatly; and the ceramic which is compact in structure and uniform in grain size, and has lower room temperature resistivity and a higher PTC effect is obtained finally. The characteristics are beneficial for meeting various functional requirements, such as high sensitivity, high reliability, imoact resistance and high safety, of a PTC ceramic sensor.

Description

A kind of PTC ceramic post sintering method

Technical field

The present invention relates to a kind of positive temperature coefficient (Positive Temperature Coefficient is abbreviated as PTC) ceramic post sintering method, belong to the electronic ceramic preparation field.

Background technology

Under the effect of scientific domain development, information is a kind of object that is detected and controls, yet obtaining of information mainly is to derive from various sensors.In the middle of various sensors, positive temperature coefficient ceramic is called for short the PTC pottery, is widely used in every field.Along with the development of microelectronics, the application of PTC ceramic components has been subject to some restrictions, shows to keep high PTC effect when reducing room temperature resistivity.Therefore, only have and reduced room temperature resistivity, the PTC ceramic components just can be applied in the overcurrent protection of microelectronic circuit and strong current circuit.The method that is commonly used to reduce the room temperature resistivity of PTC ceramic components has three kinds: the firstth, and material purity, the raw material that purity is low is difficult to obtain the PTC thermistor of low-resistance value, and causes easily PTC thermistor electrical property to worsen, and production technique is unstable; The secondth, liquid additive can receive detrimental impurity in crystal boundary, is beneficial to the purifying of crystal grain, also can enlarge the sintering warm area, reduces sintering temperature; The 3rd is sintering process, improves compactness and the homogeneity of pottery by the speed of change heating and cooling and the sintering process such as temperature and time of insulation, thereby reduces room temperature resistivity.The third method is not need to add any additive just can reduce room temperature resistivity, and can also be lowered into this, save energy, thereby used widely.

In general, the sintering method of PTC pottery mainly contains three processes: temperature raising period, soak and cooling stage.The sintering process that current industrial adopts nearly all is to carry out disposable insulation under certain temperature, then directly cooling, such technique is difficult to guarantee that the density of PTC pottery reaches 100% of theoretical density, abnormal grain growth is serious, thereby cause room temperature resistivity rising, PTC effect to weaken, be difficult to satisfy the requirement of the various functions such as highly sensitive, high reliability, shock-resistance, high security.

Summary of the invention

The objective of the invention is based on above reason, in conjunction with powder sintering kinetics, a kind of sintering method of PTC pottery is provided, this sintering method can strengthen the density of PTC pottery effectively, suppress the misgrowth of crystal grain, obtain the PTC pottery than low room temperature resistivity and higher voltage endurance.

Concrete steps are:

(1) positive temperature coefficient that binder removal is later (PTC) biscuit of ceramics is put into crucible, and furnace temperature rises to 1300 ~ 1380 ℃ with the temperature rise rate of 3 ~ 7 ℃/min, is incubated 0 ~ 10 minute, makes the density of pottery reach more than 75% of theoretical density.

(2) after step (1) was finished, furnace temperature was down to 1100 ~ 1190 ℃ with the rate of temperature fall of 100 ~ 200 ℃/min, was incubated 120 ~ 240 minutes, made the density of pottery reach more than 97% of theoretical density.

(3) after step (2) was finished, furnace temperature rose to 1200 ~ 1280 ℃ with the temperature rise rate of 80 ~ 150 ℃/min, was incubated 90 ~ 180 minutes, made the density of pottery reach theoretical density, then furnace cooling.

The purpose of stages of the present invention is: the PTC biscuit of ceramics is raised to 1300 ~ 1380 ℃ from room temperature, is incubated 0 ~ 10 minute, and this moment, the density of sintering block reached more than 75% of theoretical density, like this so that in the sintering block all pores all play pendulum.Then fast cooling to 1100 ~ 1190 ℃, be incubated 120 ~ 240 minutes, this moment, the dynamic evolution of microtexture was very slow, can very effective inhibition crystal boundary migration, and this slowly power is enough for having reached fully dense pottery, can also limit simultaneously the abnormal growth of particle diameter, guarantee the size uniform of crystal grain.Yet this process needs extremely very long soaking time just can reach complete densification usually.Therefore, consider from the angle of save energy, after this insulation regular hour in stage, stove is rapidly heated 1200 ~ 1280 ℃ again, be incubated 90 ~ 180 minutes, make sintering block quick densifying, reach theoretical density.The invention has the beneficial effects as follows: the sintering block is incubated at lesser temps after experiencing higher sintering temperature, the quick travel that has suppressed crystal boundary, tiny and the uniform sintering block of crystal grain can be obtained, and further in slightly high Temperature Treatment, sintering time can be reduced greatly.Finally obtain compact structure, even grain size, have the pottery than low room temperature resistivity and higher PTC effect.

Description of drawings

Fig. 1 is the sintering method curve of the PTC pottery of the embodiment of the invention 1.

Fig. 2 is the resistance-temperature characteristic curve of the PTC pottery of the embodiment of the invention 1.

Fig. 3 is the sintering method curve of the PTC pottery of the embodiment of the invention 2.

Fig. 4 is the resistance-temperature characteristic curve of the PTC pottery of the embodiment of the invention 2.

Fig. 5 is the sintering method curve of the PTC pottery of the embodiment of the invention 3.

Fig. 6 is the resistance-temperature characteristic curve of the PTC pottery of the embodiment of the invention 3.

Embodiment

Below will describe the present invention by embodiment, the purpose that these embodiment just illustrate for exemplary, and be not for limiting the present invention.Among the embodiment related PTC biscuit of ceramics be by barium titanate, plumbous oxide, titanium dioxide, silicon-dioxide, manganous nitrate, Niobium Pentxoxide according to certain proportioning, make through techniques such as batch mixings, calcining, ball milling, granulation, moulding.The density of related pottery all adopts Archimedes's method test gained among the embodiment.

Embodiment 1:

(1) positive temperature coefficient that binder removal is later (PTC) biscuit of ceramics is put into crucible, and furnace temperature rises to 1300 ℃ with the temperature rise rate of 3 ℃/min, is incubated 0 minute, and the density of pottery reaches 76% of theoretical density.

(2) after step (1) was finished, furnace temperature was down to 1100 ℃ with the rate of temperature fall of 200 ℃/min, was incubated 120 minutes, and the density of pottery reaches 98% of theoretical density.

(3) after step (2) is finished, furnace temperature rises to 1200 ℃ with the temperature rise rate of 80 ℃/min, is incubated 90 minutes, and the density of pottery reaches theoretical density, then furnace cooling, the pottery that finally obtains compact structure, even grain size, has low room temperature resistivity and higher PTC effect.

Fig. 1 has provided the synoptic diagram of this sintering method.Through test, room temperature resistance reaches 7237 Ω, and the resistivity-temperature characteristics of the PTC pottery of gained as shown in Figure 2.

Embodiment 2:

(1) positive temperature coefficient that binder removal is later (PTC) biscuit of ceramics is put into crucible, and furnace temperature rises to 1350 ℃ with the temperature rise rate of 5 ℃/min, is incubated 5 minutes, and the density of pottery reaches 79% of theoretical density.

(2) after step (1) was finished, furnace temperature was down to 1150 ℃ with the rate of temperature fall of 150 ℃/min, was incubated 180 minutes, and the density of pottery reaches 98% of theoretical density.

(3) after step (2) is finished, furnace temperature rises to 1250 ℃ with the temperature rise rate of 100 ℃/min, is incubated 140 minutes, and the density of pottery reaches theoretical density, then furnace cooling, the pottery that finally obtains compact structure, even grain size, has low room temperature resistivity and higher PTC effect.

Fig. 3 has provided the synoptic diagram of this sintering method.Through test, room temperature resistance reaches 548 Ω, and the resistivity-temperature characteristics of the PTC pottery of gained as shown in Figure 4.

Embodiment 3:

(1) positive temperature coefficient that binder removal is later (PTC) biscuit of ceramics is put into crucible, and furnace temperature rises to 1380 ℃ with the temperature rise rate of 7 ℃/min, is incubated 10 minutes, and the density of pottery reaches 83% of theoretical density.

(2) after step (1) was finished, furnace temperature was down to 1190 ℃ with the rate of temperature fall of 100 ℃/min, was incubated 240 minutes, and the density of pottery reaches 99% of theoretical density.

(3) after step (2) is finished, furnace temperature rises to 1280 ℃ with the temperature rise rate of 150 ℃/min, is incubated 180 minutes, and the density of pottery reaches theoretical density, then furnace cooling, the pottery that finally obtains compact structure, even grain size, has low room temperature resistivity and higher PTC effect.

Fig. 5 has provided the synoptic diagram of this sintering method.Through test, room temperature resistance reaches 220 Ω, and the resistivity-temperature characteristics of the PTC pottery of gained as shown in Figure 6.

Claims

1. a positive temperature coefficient is the sintering method that Positive Temperature Coefficient is abbreviated as the PTC pottery, it is characterized in that concrete steps are:

(1) positive temperature coefficient ceramic that binder removal is later is that the PTC biscuit of ceramics is put into crucible, and furnace temperature rises to 1300 ~ 1380 ℃ with the temperature rise rate of 3 ~ 7 ℃/min, is incubated 0 ~ 10 minute, makes the density of pottery reach more than 75% of theoretical density;

(2) after step (1) was finished, furnace temperature was down to 1100 ~ 1190 ℃ with the rate of temperature fall of 100 ~ 200 ℃/min, was incubated 120 ~ 240 minutes, made the density of pottery reach more than 97% of theoretical density;