Preparation method of fluorescent ceramic containing aluminum oxide matrix and related fluorescent ceramic

A technology of fluorescent ceramics and alumina, applied in the preparation of fluorescent ceramics and related fluorescent ceramics field, can solve the problems of low thermal conductivity and low luminous efficiency of fluorescent ceramics, and achieve high thermal conductivity, high luminous efficiency, and improved thermal conductivity. Effect

Active Publication Date: 2017-10-24
APPOTRONICS CORP LTD
5 Cites 23 Cited by

AI-Extracted Technical Summary

Problems solved by technology

[0005] In view of the defects of low thermal conductivity and low luminous efficiency of the prepared fluorescent ceramics in the above-mentioned prior art, the present i...
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Method used

As described in the background technology, the preparation of fluorescent ceramics in the prior art is obtained by sintering fluorescent powder raw materials (i.e. various oxides), and has certain requirements for its translucency, and the fluorescent ceramics obtained in this way emit light The efficiency is obviously lower than that of phosphor powder prepared from the same raw material, and the thermal conductivity of YAG ceramics is low, which is very unfavorable for heat dissipation during use. The invention prepares fluorescent ceramics with alumina matrix, directly adopts existing commercial fluorescent powder as raw material, does not go through the steps of fluorescent powder preparation in the preparation process, and avoids various problems brought about by the growth process of fluorescent powder grains in the preparation of fluorescent ceramics. At the same time, through the selection of alumina with small particle size and the high-pressure treatment process, the alumina matrix of the fluorescent ceramics produced is dense and has high thermal conductivity, and the finished product has good heat dissipation performance.
Because the melting point of fluorescent powder and aluminum oxide is close, and slightly lower than the melting point of aluminum oxide (as the melting point of YAG is 1950 ℃, the melting point of aluminum oxide is 2050 ℃), in the preparation process, when aluminum oxide enters the liquid phase At the same time, the original structure of the phosphor powder is easily destroyed, and the luminous efficiency of the alumina-based fluorescent ceramics obtained in this way is low. In the present invention, the particle size of the alumina powder is much smaller than that of the phosphor powder by selecting the alumina powder and the phosphor powder with a suitable particle size, which reduces the temperature required for the alumina powder to enter the liquid phase without reducing the temperature required for the phosphor powder to enter the liquid phase. The temperature ensures that the phosphor powder can maintain a stable physical structure at the sintering temperature, so that the phosphor powder has the high luminous efficiency of the large particle size phosphor powder. In addition, the small particle size of alumina enables the high-pressure treatment in the preparation process to fully fill the pores in the fluorescent ceramics, which improves the density of the prepared fluorescent ceramics (thereby improving thermal conductivity and light transmission properties). In addition, the present invention introduces a magnesia-yttria mixed sintering aid in the preparation process, the sintering aid first enters the liquid phase during the sintering process, and promotes the alumina to enter the liquid phase at a lower temperature, which plays a role in promoting sintering. The role of the sintered body not only improves the thermal conductivity and light transmission performance of the sintered body, but also ensures that as much phosphor powder as possible is not affected by the high temperature during the sintering process, and the physical structure and surface morphology can be kept stable, thus making the phosphor The obtained ...
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Abstract

The invention provides a preparation method of a fluorescent ceramic containing aluminum oxide matrix. The preparation method sequentially comprises the following steps: mixing aluminum oxide, fluorescent powder and a sintering additive and calcining to obtain fluorescent ceramic precursor powder; sintering the powder to obtain the fluorescent ceramic. The grain diameter of each component is selected to be a pre-set size and the fluorescent ceramic precursor powder is subjected to high-pressure treatment under the condition of 5MPa or above before a sintering process; the fluorescent ceramic precursor powder bears the high pressure of 30MPa to 200MPa in the sintering process and the sintering temperature is 1250 DEG C to 1550 DEG C; the sintering is carried out under an oxygen-free atmosphere. According to the preparation method provided by the invention, the aluminum oxide enters a liquid phase at relatively low temperature under the condition that the fluorescent powder has an unchanged crystal new look in a preparation process and the uniform and dense fluorescent ceramic with low porosity is obtained; the heat-conducting performance and luminous efficiency of the fluorescent ceramic are extremely improved.

Application Domain

Luminescent compositions

Technology Topic

FluorescenceHigh pressure +9

Image

  • Preparation method of fluorescent ceramic containing aluminum oxide matrix and related fluorescent ceramic

Examples

  • Experimental program(4)

Example Embodiment

[0024] like figure 1 It is a flowchart of a method for preparing fluorescent ceramics according to an embodiment of the present invention. As shown in the figure, the preparation method includes the following steps in sequence:
[0025] ① Mixing: uniformly mix alumina, fluorescent powder, sintering aid and grinding solvent to obtain fluorescent ceramic precursor slurry. ~0.1μm;
[0026] ②Calcination: Dry the fluorescent ceramic precursor slurry, and then calcinate it in an aerobic atmosphere to remove water and organic matter, and obtain fluorescent ceramic precursor powder;
[0027] ③ Sintering: Sinter the fluorescent ceramic precursor powder to obtain fluorescent ceramics. The sintering temperature is 1250-1550°C, the sintering pressure is 30-200MPa, and the sintering is carried out in an oxygen-free atmosphere. High pressure pretreatment above 5MPa.
[0028] In the mixing step, the first is the selection of raw materials. In this embodiment, ultra-fine alumina powder with a small particle size is selected, and the particle size is 0.05-1 μm. More preferably, alumina powder with a particle size of 0.06-0.2 μm is selected; The particle size is much larger than that of alumina, ranging from 10 to 30 μm. In general, phosphor YAG:Ce 3+ The melting point of aluminum oxide is about 1970°C, while the melting point of alumina is 2050°C. Before the alumina enters the liquid phase, the physical structure of the phosphor has been destroyed. Even if such a phosphor is reshaped, its luminous efficiency will drop significantly. In this embodiment, the nano-scale alumina powder is used, which can greatly reduce the temperature at which it enters the liquid phase, so that the alumina can enter the liquid phase before the phosphor powder, avoiding damage to the physical structure of the phosphor powder. In this embodiment, the fluorescent powder is YAG:Ce 3+ , you can also choose LuAG:Ce 3+ , YAG doped lanthanide phosphors or LuAG doped other lanthanide phosphors. The sintering aid is a magnesia-yttria mixed sintering aid. Experiments have proved that this sintering aid acts on the surface of alumina without affecting the surface morphology of phosphor powder.
[0029]In this embodiment, the phosphor powder accounts for 30-80% by mass of the phosphor ceramic precursor powder. Phosphor powder as the luminescent center must have a sufficient amount to ensure the luminous intensity of fluorescent ceramics, and the higher the specific gravity of phosphor powder, the more conducive to the improvement of the maximum luminous intensity of fluorescent ceramics; however, alumina as a matrix must achieve sufficient The amount can ensure continuous distribution, so the phosphor should not be too much. The mass percentage of sintering aids in the total powder is 0.01-1%, and the effect is not obvious when the amount of sintering aids is too small; but when the amount of sintering aids is too much, exceeding 1wt%, it will limit the growth of alumina, and The generation of impurity phases reduces the thermal conductivity and light transmittance of fluorescent ceramics.
[0030] In this embodiment, ball milling is used for mixing. First, weigh a certain amount of alumina powder, put it into a ball mill tank, add an appropriate amount of grinding solvent (such as ethanol), thickener and dispersant, and then conduct the first ball mill to obtain a viscous suspension slurry, then add Phosphor powder is subjected to second ball milling to finally obtain fluorescent ceramic precursor slurry. This embodiment adopts the method of two-step ball milling, the first ball milling time is longer than the second ball milling time, so that the alumina powder with small particle size and difficult to disperse uniformly can be fully dispersed first, and then add phosphor powder for ball milling to avoid fluorescence The ball milling of the powder for a long time reduces the damage to the phosphor powder during the ball milling process.
[0031] In the calcining step, the purpose of this step is to remove impurities such as grinding solvent, thickener, and dispersant in the slurry obtained in the mixing step to obtain high-purity fluorescent ceramic precursor powder.

Example Embodiment

[0041] Embodiment one
[0042] The raw materials are high-purity ultra-fine alumina nano-powder with a particle size of 0.08-0.2 μm, high-purity ultra-fine nano-yttrium oxide powder with a particle size of 0.05-0.1 μm, and high-purity ultra-fine nano-magnesia powder with a particle size of 0.05-0.1 μm. 0.05-0.1μm, choose YAG:Ce 3+ Phosphor powder, the particle size is 15-20μm.
[0043] Weigh a certain amount of alumina powder (39.9wt%), yttrium oxide powder (0.05wt%), magnesium oxide powder (0.05wt%) and YAG:Ce 3+ Phosphor powder (60wt%). Put alumina powder, yttrium oxide powder and magnesium oxide powder into a polytetrafluoroethylene ball mill jar, add an appropriate amount of ethanol as a grinding solvent, add an appropriate amount of ceramic dispersant as a dispersant, and use ultra-low loss rate zirconia balls Carry out ball milling for the first time, and the ball milling time is 5h.
[0044] After the first ball milling, add YAG:Ce 3+ The fluorescent powder is put into the ball milling tank for the second ball milling, and the ball milling time is 20 minutes.
[0045] After two rounds of ball milling, vacuum constant temperature drying was used to obtain a dry powder.
[0046] The dry powder is calcined at 500° C. in a muffle furnace to remove organic components in the powder for 2 hours. The calcined powder is sieved and granulated to obtain a highly fluid fluorescent ceramic precursor powder.
[0047] Weigh an appropriate amount of fluorescent ceramic precursor powder and put it into a graphite mold, pre-compress it under a pressure of 5 MPa, then put the graphite mold into a hot-press sintering furnace, and sinter in an argon atmosphere at a sintering temperature of 1250°C, hold for 8 hours, and sinter The pressure is 200MPa. After the sintering is completed, the pressure is released and cooled with the furnace to obtain a fluorescent ceramic composite material with an alumina matrix.

Example Embodiment

[0048] Embodiment two
[0049] The raw materials are high-purity ultra-fine alumina nano-powder with a particle size of 0.08-0.2 μm, high-purity ultra-fine nano-yttrium oxide powder with a particle size of 0.05-0.1 μm, and high-purity ultra-fine nano-magnesia powder with a particle size of 0.05-0.1 μm. 0.05-0.1μm, choose YAG:Ce 3+ Phosphor powder, the particle size is 15-20μm.
[0050] Take a certain amount of alumina powder (30wt%), yttrium oxide powder (0.5wt%), magnesium oxide powder (0.5wt%) and YAG:Ce 3+ Phosphor powder (69wt%). Put alumina powder, yttrium oxide powder and magnesium oxide powder into a polytetrafluoroethylene ball mill jar, add an appropriate amount of ethanol as a grinding solvent, add an appropriate amount of ceramic dispersant as a dispersant, and use ultra-low loss rate zirconia balls Carry out the first ball milling, and the ball milling time is 24h.
[0051] After the first ball milling, add YAG:Ce 3+ The fluorescent powder is put into the ball mill tank, and the second ball mill is carried out, and the ball milling time is 40 minutes.
[0052] After two rounds of ball milling, vacuum constant temperature drying was used to obtain a dry powder.
[0053] The dry powder is calcined at 600° C. in a muffle furnace to remove the organic components in the powder for 2 hours. The calcined powder is sieved and granulated to obtain a highly fluid fluorescent ceramic precursor powder.
[0054] Weigh an appropriate amount of fluorescent ceramic precursor powder and put it into a graphite mold, pre-compress it under a pressure of 15 MPa, then put the graphite mold into a discharge plasma sintering furnace, and sinter it under vacuum at a sintering temperature of 1450°C, hold for 2 hours, and a sintering pressure of 40MPa. After the sintering is completed, the pressure is released and cooled with the furnace to obtain a fluorescent ceramic composite material with an alumina matrix.

PUM

PropertyMeasurementUnit
Particle size0.05 ~ 0.1µm
Particle size0.05 ~ 1.0µm
Melting point1970.0°C

Description & Claims & Application Information

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