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Room temperature high-electrocaloric effect lead-free relaxation ferroelectric ceramic preparation method

An electric card effect, ferroelectric ceramic technology, applied in the field of refrigeration devices, can solve the problems of limited application scope, unsuitable for practical application, and no

Active Publication Date: 2017-07-11
TONGJI UNIV
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  • Application Information

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Problems solved by technology

At present, research on electric cards mainly focuses on lead-containing systems, such as Pb(Zr,Ti)O 3 ,Pb(Mg 1 / 3 Nb 2 / 3 )O 3 -PbTiO 3 system, but lead is very harmful to the environment and the human body, so it is necessary to study the electrical carding effect of lead-free relaxor ferroelectric materials
[0003] In recent years, there have also been reports on the electrocardiographic effect of sodium bismuth titanate-based ceramics, but there are mainly two problems: 1) such as the 0.18Bi reported by F.L.Goupil 0.5 Na 0.5 TiO 3 -0.82Bi 0.5 K 0.5 TiO 3 System, although the temperature change ΔT ~ 0.7K induced by the electric field E = 2.2kV / mm, the temperature corresponding to the large electric card effect is too high T = 160°C, which is not suitable for practical application
at 0.94Bi 0.5 Na 0.5 TiO 3 -0.06KNbO 3 In the system, the temperature change ΔT ~ 0.8K induced by the electric field E = 5kV / mm, the temperature corresponding to the large electric card effect is too high T = 120°C, which is also not suitable for practical application
On the other hand, according to existing literature reports, the electric card effect of most sodium bismuth acid-based ceramics is measured by indirect measurement (by the formula calculated), since bismuth sodium titanate-based ferroelectric ceramics is a typical relaxor ferroelectric, the application of indirect measurement method is inaccurate
[0004] Chinese patent CN102173788A discloses a bismuth sodium titanate-based high-strain lead-free piezoelectric ceramic, and also discloses a preparation method of this bismuth sodium titanate-based high-strain lead-free piezoelectric ceramic, which is used to solve the existing lead-based piezoelectric ceramics. Technical Problems of Low Strain of Electroceramics
The bismuth sodium titanate-based high-strain lead-free piezoelectric ceramic disclosed in the above-mentioned patent is mainly used in devices such as drivers because of its high strain characteristics. However, this piezoelectric ceramic does not have a high electrical effect, which limits its scope of application

Method used

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  • Room temperature high-electrocaloric effect lead-free relaxation ferroelectric ceramic preparation method
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  • Room temperature high-electrocaloric effect lead-free relaxation ferroelectric ceramic preparation method

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Experimental program
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Embodiment 1

[0030] (1) select the raw material Bi whose purity is greater than 99% 2 o 3 , Na 2 CO 3 , BaCO 3 , SrCO 3 ,TiO 2 As the raw material of bismuth sodium titanate based lead-free relaxor ferroelectric ceramics. According to the chemical formula 0.86Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 -0.08 (Sr 0.7 Bi 0.2 □ 0.1 )TiO 3 Weighing, adding absolute ethanol to the nylon tank for ball milling, discharging, and drying. The ball milling time was 8 hours, and the drying temperature was 120°C. Put the dried powder into a corundum crucible, tamp it, cover the crucible, put it into a muffle furnace for calcination, raise it to 850 ℃ at 5°C / min, keep it warm for 2 hours, and calcine twice.

[0031] (2) Secondary ball milling of the synthesized powder obtained in step (1), discharging and drying. The drying temperature is the same as in step (1), and the ball milling time is 12 hours. Add an appropriate amount of 5wt% PVA to the dried powder for granulation, and press molding unde...

Embodiment 2

[0038] (1) select the raw material Bi whose purity is greater than 99% 2 o 3 , Na 2 CO 3 , BaCO 3 , SrCO 3 ,TiO 2 As the raw material of bismuth sodium titanate based lead-free relaxor ferroelectric ceramics. According to the chemical formula 0.86Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 -0.08 (Sr 0.7 Bi 0.2 □ 0.1 )TiO 3 Weighing, adding absolute ethanol to the nylon tank for ball milling, discharging, and drying. The ball milling time was 8 hours, and the drying temperature was 120°C. Put the dried powder into a corundum crucible, tamp it, cover the crucible, put it into a muffle furnace for calcination, raise it to 850 ℃ at 5°C / min, keep it warm for 2 hours, and calcine twice.

[0039] (2) Secondary ball milling of the synthesized powder obtained in step (1), discharging and drying. The drying temperature is the same as in step (1), and the ball milling time is 12 hours. Add an appropriate amount of 5wt% PVA to the dried powder for granulation, and press molding unde...

Embodiment 3

[0046] (1) select the raw material Bi whose purity is greater than 99% 2 o 3 , Na 2 CO 3 , BaCO 3 , SrCO 3 ,TiO 2 As the raw material of bismuth sodium titanate based lead-free relaxor ferroelectric ceramics. According to the chemical formula 0.86Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 -0.08 (Sr 0.7 Bi 0.2 □ 0.1 )TiO 3 Weighing, adding absolute ethanol to the nylon tank for ball milling, discharging, and drying. The ball milling time was 8 hours, and the drying temperature was 120°C. Put the dried powder into a corundum crucible, tamp it, cover the crucible, put it into a muffle furnace for calcination, raise it to 850 ℃ at 5°C / min, keep it warm for 2 hours, and calcine twice.

[0047] (2) Secondary ball milling of the synthesized powder obtained in step (1), discharging and drying. The drying temperature is the same as in step (1), and the ball milling time is 12 hours. Add an appropriate amount of 5wt% PVA to the dried powder for granulation, and press molding unde...

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Abstract

The invention relates to a room temperature high-electrocaloric effect lead-free relaxation ferroelectric ceramic preparation method, wherein the ceramic is obtained through an ordinary sintering method. According to the present invention, the raw materials do not contain lead, such that the obtained material is the environmentally friendly material; compared to the material in the prior art, the material of the present invention has the following characteristics that the system has the high electrocaloric effect when the component is positioned in the vicinity of the ergodic and non-ergodic boundary; and the process of the method is simple, and the obtained material has the high electrocaloric effect, is the excellent electrocaloric effect material, and can be used for the development of the high refrigeration efficiency solid-state refrigeration system.

Description

technical field [0001] The invention belongs to the field of refrigeration devices, and in particular relates to a preparation method of lead-free relaxor ferroelectric ceramics with high electric card effect at room temperature. Background technique [0002] At present, the refrigerating substances used in refrigeration devices are mainly chlorofluorocarbons, because chlorofluorocarbons will destroy the ozone layer in the atmosphere and increase the greenhouse effect, thereby destroying the ecological environment. As countries around the world pay more and more attention to the environment, it is the general trend to stop the use of chlorofluorocarbons. Therefore, it is necessary to develop a high-efficiency, low-cost and environment-friendly refrigeration technology. Refrigeration technology based on the electric card effect has attracted the attention of many researchers in recent years. The electric card effect refers to, in polar materials, the reversible temperature c...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/475
CPCC04B35/475C04B2235/3201C04B2235/3213C04B2235/3215C04B2235/442C04B2235/72C04B2235/96
Inventor 翟继卫李峰刘星李朋沈波
Owner TONGJI UNIV
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