Method for preparing V2O3 and its dopant nano-crystal grain ceramic

A nano-grain and dopant technology, which is applied in the field of preparation of V2O3 and its dopant nano-grain ceramics, can solve the problems of poor electrical stability of ceramics, serious furnace loss, high production cost, etc., and achieve low forming pressure , low energy consumption, low cost effect

Inactive Publication Date: 2005-04-06
SUN YAT SEN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This sintering process has high temperature, long time, high requirements for the materials used in the furnace body, and serious loss of the furnace body, so the investment is large, the energy consumption is high, and the production cost is high. In addition, only micron grain ceramics can be obtained, and the electrical stability of ceramics is poor. Difficult to implement

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0019] with V 2 o 5 , the reaction of oxalic acid and hydrochloric acid to prepare VOCl 2 solution, and then react this solution with ammonium bicarbonate to synthesize the vanadyl (IV) basic ammonium carbonate precursor. The precursor is ultrasonically crushed to a particle size of 1-2 μm, and then reduced and pyrolyzed at 400 ° C for 60 minutes under hydrogen flow to obtain V 2 o 3 Nano-powder. The powder is pressed at 300MPa, placed in a tube furnace or tunnel furnace, and filled with water-saturated H 2 Exclude the air in the furnace, then heat it to 1400°C and keep it for 5 minutes, then cool it down to 800-900°C with a program and then cool it naturally. The average particle diameter is about 60nm, and the crystal grain is spherical nano-V 2 o 3 ceramics. Its Tt 1 At about -120°C, the resistivity jump is greater than 5 orders of magnitude.

Embodiment 2

[0021] Apply the method similar to embodiment 1, use VOCl 2 solution, CrCl 3 The Cr-doped vanadyl (IV) basic ammonium carbonate precursor was synthesized by reacting the solution with ammonium bicarbonate. The Cr-doped precursor was ultrasonically crushed to a particle size of 1-2 μm, and then reduced and pyrolyzed at 800°C for 20 minutes under hydrogen flow to obtain (V 0.993 Cr 0.007 ) 2 o 3 Nano powder. This powder is pressed into tablets under 150MPa, then sintered at 1250°C for 15min with the same method as in Example 1, to obtain agglomerate sintered body of 2-3 μm, the average diameter of crystal grains is less than 100nm, and the crystal form is quasi-spherical (V 0.993 Cr 0.007 ) 2 o 3 ceramics. Its Tt 2 At about 77°C, the resistivity jump is greater than 2 orders of magnitude.

Embodiment 3

[0023] Apply the method similar to embodiment 1, use VOCl 2 solution, AlCl 3Solution and ammonium bicarbonate were reacted to synthesize Al-doped vanadyl (IV) basic ammonium carbonate precursor, and the Al-doped precursor was ultrasonically crushed to a particle size of 1-2 μm, and then reduced and pyrolyzed at 600°C for 40 minutes under hydrogen flow to obtain (V 0.986 Al 0.014 ) 2 o 3 Nano-powder. This powder is compressed at 200MPa, and then passed through H 2 Sintered at 1150°C for 80min, the agglomerate sintered body is about 1.5μm, the average grain diameter is less than 100nm, and the crystal shape is quasi-spherical (V 0.986 Al 0.014 ) 2 o 3 ceramics. Its Tt 2 At about -65°C, the resistivity jumps by about 3 orders of magnitude.

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PUM

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Abstract

The invention relates to a method to produce V2O3 and Cr3+ or Al3+ mixed globular shape or torispherical nanometer particle positive temperature coefficient temperature sensing series ceramics. The method can gain V2O3 mixed nanometer powder by chemical doping method. After pressing into piece, first gaining particle of ceramics that has an average particle diameter less than 100nm in the H2 gas, low sintering temperature and short sintering span. This series ceramics has high mechanical strength, stable electrical property and small range of critical temperature. The invention discloses simple structure, low energy consumption, low cost and no pollution.

Description

technical field [0001] The present invention relates to a V 2 o 3 The invention relates to a preparation method of the dopant nano-grain ceramics. Background technique [0002] V 2 o 3 There are two phase transition temperatures (Tt) in ceramics, and the first phase transition point Tt exists around -120°C 1 , showing a negative temperature coefficient (NTC), and the resistivity jumps about 7 to 8 orders of magnitude. When doped with a small amount of impurity Cr 3+ or Al 3+ , the phase transition temperature Tt of the NTC phase transition 1 With the increase of doping amount, it moves to high temperature, and at the same time, the second phase transition point Tt appears at -70 ~ 180 °C 2 , and has a positive temperature coefficient (PTC), the phase transition temperature Tt of the PTC phase transition 2 As the doping amount increases, it moves to a lower temperature. with BaTiO 3 Compared with other PTC materials, they have the following advantages: (1) The crit...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/495C04B35/626C04B35/64
Inventor 郑臣谋雷德铭储向峰韦柳娅
Owner SUN YAT SEN UNIV
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