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Method for preparing bismuth ferrite based multifunctioanl oxide ceramic material

A technology based on oxide ceramics and bismuth ferrite, applied in the field of material science, can solve the problems of poor repeatability of results, low density, and inability to prepare bulk ceramics.

Inactive Publication Date: 2007-10-10
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, this method has the following disadvantages: 2 o 3 and Fe 2 o 3 There are very strict requirements on the particle size and mixing uniformity of the two powders. Submicron oxide powders must be used, and the mixing must be uniform enough to obtain single-phase BiFeO 3 Ceramics; at the same time, due to the short sintering time, rapid temperature rise, difficult operability, and poor repeatability of the results; the flexibility of the sintering process is poor, and the sintering temperature of 860°C is strictly limited, and impurities will be generated if it is too high or too low; in addition , the rapid heating and cooling treatment is prone to cracks and other defects, and the density is low, so large ceramics cannot be prepared

Method used

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  • Method for preparing bismuth ferrite based multifunctioanl oxide ceramic material
  • Method for preparing bismuth ferrite based multifunctioanl oxide ceramic material
  • Method for preparing bismuth ferrite based multifunctioanl oxide ceramic material

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Experimental program
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Effect test

Embodiment 1

[0033] Mix ferric nitrate, lanthanum nitrate and citric acid according to a certain stoichiometric ratio (the molar ratio of citric acid and all metal ions is 1.5:1), prepare a transparent solution, heat and stir for several hours to form a viscous sol, then mix and add ammonia water to adjust pH to 1. The stoichiometric ratio of bismuth nitrate was then added slowly to avoid precipitation of bismuth subnitrate. Stir for 30 minutes to make it fully mixed, place in an oven, and keep warm at 120°C to form a xerogel. The temperature of the gel was slowly raised to 200°C, and a dark fire self-propagating decomposition reaction occurred to remove organic matter. Rapid heat treatment was performed at 860°C and kept for 5 minutes to obtain BLTFO8 powder. X-ray diffraction analysis (XRD) test results show that the phase is single-phase powder with R3c structure. At room temperature, under a test magnetic field of 60kOe, the saturation magnetization can reach 1.4emu / g, and the residu...

Embodiment 2

[0035] Weigh an appropriate amount of BLTFO8 powder, put it into a graphite mold (Ф15mm), and compact it at 20MPa; then move the mold into an SPS sintering furnace, and use the traditional SPS method for sintering. Rise to 600°C within 3 minutes, then rise to the sintering temperature at a speed of 50°C / min, keep the temperature for several minutes to sinter the sample. After the sintering is completed, the sample is taken out, and the carbon is removed by heat treatment at 650°C for 2 hours. The dielectric properties of ceramics are very sensitive to the sintering temperature: when sintered below 690°C, the ceramic loss is low (tanδ is below 10%), the dielectric constant is stable (about 120), the ceramic density is low, and the grain size is about 1 micron ; When the temperature exceeds 690°C, the loss of ceramics increases significantly and the dielectric properties deteriorate. As shown in Figure 3, Figure 4, and Figure 5.

Embodiment 3

[0037] Weigh an appropriate amount of BLTFO8 powder, pre-press 20MPa into a disc of Ф12×2mm; add a small amount of Al 2 o 3 Put the powder into the graphite mold (Ф15mm) and compact it at 20MPa; move the pressed tablet into the Al 2 o 3 layer, adjust to the center position; continue to add Al to the mold 2 o 3Embed the BLTFO8 disc with powder and compact it with 20MPa; then move the mold into the SPS sintering furnace, raise it to 600°C within 3 minutes, then raise it to the sintering temperature at a speed of 50°C / min, and keep the temperature for several minutes to sinter the sample. The sintering pressure is 50MPa. After the sintering is completed, the sample is taken out, and the outer Al 2 o 3 The powder is removed to obtain BLTFO8 ceramics. When sintered below 850°C, the dielectric properties of ceramics are not sensitive to temperature changes, the ceramics have high density (>99%), low loss (tanδ2 . As shown in Figure 6, Figure 7, and Figure 8.

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Abstract

This invention relates to a method for preparing BiFeO3-based multifunctional oxide ceramic. The method comprises: (1) pre-pressing BLTFO8 powder into a disc, loading oxide protective powder (Al2O3, CeO2, ZrO2 or FeO) into a graphite mold, and pressing; (2) transferring the BLTFO8 disc onto the oxide protective powder layer in the mold; (3) continuing adding oxide protective powder into the mold to embed the BLTFO8 disc, and pressing; (4) transferring the mold into an SPS sintering furnace, heating to 600 deg.C within 3 min, then heating to the sintering temperature at a rate of 50 deg.C / min, keeping the temperature, and sintering. Since BiFeO3 has G-type antiferromagnetic structure, doping with rare earth element such as La or Tb, or metal element such as Ba or K can alter its antiferromagnetic structure, and the obtained BiFeO3-based multifunctional oxide ceramic has ferromagnetism at room temperature. The method can inhibit the valency change of the elements and reduce loss, and the BiFeO3-based multifunctional oxide ceramic has good ferroelectric and ferromagnetic properties at room temperature.

Description

technical field [0001] The invention belongs to the field of material science, particularly the preparation and sintering method of multifunctional oxide ceramic materials, mainly related to bismuth ferrite (BiFeO 3 )-based new ferroelectric-ferromagnetic functional ceramic materials and embedded spark plasma sintering (SPS) technology. Background technique [0002] With the continuous development of electronic information technology, especially hybrid integrated circuit and surface packaging technology, more and more attention has been paid to new functional ceramic components, and its development trend is mainly reflected in the miniaturization, multi-function and integration of devices. , High reliability. Ferroelectric-ferromagnetic multifunctional materials have strong competitiveness under this development requirement. Among them, BiFeO 3 The base ceramics have both ferroelectric and ferromagnetic order at room temperature, which provides great application possibili...

Claims

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Application Information

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IPC IPC(8): C04B35/63C04B35/645C04B35/40
Inventor 南策文姜庆辉林元华沈志坚
Owner TSINGHUA UNIV
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