WO2020052256A1 - Porous fluorescent ceramic, preparation method therefor, light-emitting device and projection device - Google Patents

Abstract

A porous fluorescent ceramic, a preparation method therefor, a light-emitting device and a projection device. The porous fluorescent ceramic comprises a fluorescent ceramic phase and hole phases dispersed in the fluorescent ceramic phase, and at least a part of the hole phases are located in crystal grains of the fluorescent ceramic phase. The hole phases located inside the crystal grains can improve the uniformity of light emission, and can improve the light conversion efficiency and mechanical properties of the fluorescent ceramic.

Description

Porous fluorescent ceramic and preparation method thereof, light emitting device and projection device Technical field

The invention relates to the technical field of fluorescent ceramics, in particular to a porous fluorescent ceramic and a preparation method thereof, a light emitting device and a projection device.

Background technique

Semiconductor LED (Light Emitting Diode, light emitting diode) or LD (laser Diode, laser diode) lamps have the advantages of energy saving, environmental protection, long life, small size, light weight, sturdy structure, and low operating voltage. The fourth generation of lighting fixtures after fluorescent lamps, high-intensity gas lamps. At present, mainstream semiconductor lighting devices use blue LEDs or LDs to excite yellow wavelength conversion materials to emit yellow light, and partially unabsorbed blue and yellow light are mixed to achieve white light emission. The main problem with this solution is the uniformity of the emitted white light. The color of the emitted light depends on the ratio of the amount of unabsorbed blue light and converted yellow light. When the concentration of the activator in the wavelength conversion material is the same, compared to the blue light perpendicular to the direction of the incident optical axis, the blue light traveling far from the vertical angle has a longer optical path, and the blue light at this angle will be more strongly absorbed and converted into Yellow light, which results in the formation of a so-called "yellow ring" when viewed at a greater angle, which means that the light is not uniform.

In order to solve the problem of forming a yellow ring, thereby obtaining uniform white light, it is disclosed in the prior art to introduce a second phase as a scattering center in a fluorescent ceramic conversion material. However, the introduction of the second phase in the fluorescent ceramic conversion material can reduce the mechanical properties or light efficiency of the wavelength conversion device.

The above content is only used to assist in understanding the technical solution of the present invention, and does not mean that the above content is prior art.

Summary of the Invention

The main purpose of the present invention is to provide a porous fluorescent ceramic, which aims to solve the technical problems of poor mechanical properties and low light efficiency of the existing porous fluorescent ceramics.

To achieve the above object, the present invention provides a porous fluorescent ceramic.

A porous fluorescent ceramic includes a fluorescent ceramic phase and a pore phase dispersed in the fluorescent ceramic phase, and is characterized in that at least a part of the pore phase is located in crystal grains of the fluorescent ceramic phase. Preferably, the crystal size of the fluorescent ceramic phase is 10-20um.

Preferably, the size of the pore phase is 0.5-1.5um.

Preferably, the porosity of the porous fluorescent ceramic is 1% to 10%. More preferably, the porosity of the porous fluorescent ceramic is 3 to 5%.

Preferably, the fluorescent ceramic phase is a garnet system. More preferably, the fluorescent ceramic phase is Y ₃ Al ₅ O ₁₂ : Ce or Lu ₃ Al ₅ O ₁₂ : Ce.

Preferably, the pore phase is at least one of a spherical hole, an oval hole, or an elongated hole.

In addition, in a second aspect, the present invention also provides a light source device, including an excitation light source and any of the porous fluorescent ceramics described above, wherein the excitation light source is capable of emitting excitation light for exciting the porous fluorescent ceramic to emit light. Excited by light.

According to a third aspect, the present invention further provides a projection device, which is characterized in that it includes:

The aforementioned light source device,

A light modulation device that modulates light from the light source device according to image information to form image light, and

A projection optical system that projects the image light.

In a fourth aspect, the present invention also provides a method for preparing a fluorescent ceramic, which is characterized by including the following steps:

S1: mixing of raw materials,

The oxide raw material is weighed according to the stoichiometric ratio of the fluorescent ceramic, and the particle size of the oxide raw material is 1 to 1000 nm, and then an adhesive, a sintering aid and a solvent are added, and the raw material powder is obtained by ball milling for 8 to 24 hours;

S2: compression molding,

The raw material powder obtained in S1 is sieved, pre-pressed, and then cold isostatically compacted at 100 to 300 MPa to obtain a ceramic green body;

S3: pre-sintering excludes organics,

Pre-sintering the ceramic green body obtained from S3 in a temperature range of 600-1000 ° C for 4-10 hours to exclude organic matter;

S4: ceramic sintering,

The ceramic green body obtained by S3 is sintered in an inert atmosphere to obtain a fluorescent ceramic. The sintering time is 6 to 10 hours, the sintering temperature is 1550 to 1800 ° C, and the heating rate is 10 to 20 ° C / min.

Preferably, the oxide raw material includes yttrium oxide, cerium oxide, and alumina;

Preferably, the particle diameter of the yttrium oxide and cerium oxide is 20-50 nm;

Preferably, the particle diameter of the alumina is 100-300 nm.

The porous fluorescent ceramic of the present invention introduces a pore phase into the ceramic grains, and when the pore phase is located in the crystal grains, it is beneficial to the improvement of the mechanical properties and light efficiency of the ceramic itself. On the one hand, the pore phase inside the ceramic grains will not restrict the growth of ceramic grains. During the sintering process, the ceramic grains in the ceramic can grow larger, which is conducive to the improvement of its light efficiency. The phase is introduced into the crystal grain, which avoids the introduction of defects when the pore phase is located at the grain boundary of the ceramic grain, can prevent the ceramic from breaking along the grain boundary, and improves the mechanical properties of the fluorescent ceramic.

Therefore, when the fluorescent ceramic of the present invention is applied to a light source device, the light conversion efficiency and mechanical properties of the fluorescent ceramic can also be improved when the pore phase inside the crystal grains can improve light uniformity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

2 is a schematic structural diagram of another embodiment of the present invention;

3 is a schematic structural diagram of a light emitting device according to the present invention;

FIG. 4 is an electron micrograph of Embodiment 1 of the present invention; FIG.

FIG. 5 is another electron microscope image of Embodiment 1 of the present invention; FIG.

The realization of the purpose, functional characteristics and advantages of the present invention will be further explained with reference to the embodiments and the drawings.

detailed description

In the following, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

1 and FIG. 2, a porous fluorescent ceramic 1 provided by the present invention includes a fluorescent ceramic phase 11 and a pore phase 12 dispersed in the fluorescent ceramic phase 11. At least part of the pore phase 12 is located in the fluorescent ceramic phase. 11 in the grain.

In some embodiments, referring to FIG. 2, the porous fluorescent ceramic 1 is a polycrystalline ceramic, and the pore phase 12 dispersed in the fluorescent ceramic phase 11 specifically includes a pore phase 121 and a part of the crystalline phase 111 inside the fluorescent ceramic grain 111 The pore phase 122 is located at the grain boundary 112 of the fluorescent ceramic.

It should be noted that, in the present invention, the state of the pore phase in the ceramic can be achieved by controlling the particle diameter of the raw material and the temperature rising program.

Preferably, in some other embodiments, the pore phases 12 may all be located inside the crystal grains of the fluorescent ceramic.

It should be noted that the porous fluorescent ceramic in the above embodiment introduces the pore phase into the ceramic grains, and when the pore phase is located in the crystal grains, it is beneficial to the mechanical performance and light efficiency of the ceramic itself. On the one hand, the pore phase inside the ceramic grains will not restrict the growth of ceramic grains. During the sintering process, the ceramic grains in the ceramic can grow larger, which is conducive to the improvement of its light efficiency. The phase is introduced into the crystal grain, which avoids the introduction of defects when the pore phase is located at the grain boundary of the ceramic grain, can prevent the ceramic from breaking along the grain boundary, and improves the mechanical properties of the fluorescent ceramic. The light efficiency referred to here refers to the conversion efficiency of the excited light emitted by the excitation light to excite the fluorescent ceramics; generally speaking, shorter wavelength light is used as the excitation light, such as ultraviolet light, blue light, etc., and the wavelength of the excited light is generally longer than Excitation light, such as green light, yellow light, red light, etc.

In some specific embodiments, the grain size of the fluorescent ceramic phase is 10-20um. The grain size range of the fluorescent ceramic in the present invention is obtained through experimental optimization. When the grain size (particle diameter) is less than 10um, the grain size is too small, which is not conducive to controlling the pore phase inside the grain. When it is less than 10um, the pore phase will concentrate more on the grain boundary. When the particle size is greater than 20um, the mechanical strength of the ceramic will decrease due to the excessive grain size. Generally speaking, in dense polycrystalline ceramics, the mechanical There is a negative correlation between strength and grain size. It can be understood that although the larger grain size of the fluorescent ceramics allows the fluorescent ceramics to obtain higher light conversion efficiency, due to the consideration of the mechanical strength of the ceramics, the grain size should not be larger than 20um. By controlling the particle size of the ceramic grains, on the one hand, the specific position of the pore phase in the fluorescent ceramic phase, that is, the proportion of the pore phase in the fluorescent ceramic grain, can be controlled, and on the other hand, the light conversion efficiency and mechanical properties of the ceramic can be controlled. .

Preferably, the size of the pore phase is 0.5-1.5um. It can be understood that if the size of the pore phase is too small, that is, less than 0.5 um, it is difficult to maintain stability during the preparation of the fluorescent ceramic, and it will diffuse and collect into a larger pore phase during sintering at high temperature. However, if the pore phase is too large, that is, greater than 1.5um, on the one hand, it is difficult to realize due to the limitation of the preparation process and raw materials, and on the other hand, the light emitted by the excitation light source will be backscattered in the fluorescent ceramic, resulting in available light. Reduce, reduce the light conversion efficiency of the entire fluorescent ceramic or light source device.

Preferably, the porosity of the porous fluorescent ceramic is 1% to 10%. More preferably, the porosity of the porous fluorescent ceramic is 3 to 5%. It should be noted that the "porosity" is defined as a unitless number and represents the proportion of the total volume occupied by the pore phase volume of the article. Specifically, in this embodiment, the ratio of the volume of the pore phase to the volume of the fluorescent ceramic is referred to. Similarly, the porosity is too small, the transparency of the fluorescent ceramic is too large, the scattering effect on the excitation light is reduced, and the uniform light effect cannot be achieved. When the porosity is too large, the backscatter of the fluorescent ceramic increases, which reduces the light conversion efficiency of the entire fluorescent ceramic or the light source device. Here, backscattering means that the excitation light incident on the fluorescent ceramic is directly scattered out of the fluorescent ceramic from the incident direction (that is, the incident surface) without conversion. Since this part of the backscattered excitation light does not participate in the excitation of the fluorescent ceramic, Therefore, the increase in backscattering reduces the light conversion efficiency of the fluorescent ceramic or the light source device.

It can be understood that the key point in the above embodiment is to determine the parameter range of the number of pore phases (that is, porosity) and the size (the size of the pore phases) in the fluorescent ceramics, so that the fluorescent ceramics have uniformity in color and A balance is achieved between scattered and reduced light efficiency, ensuring the overall performance of the fluorescent ceramic. In addition, the above porosity range and / or the target average pore phase size range solves this problem and is optimal for scattering. At the same time, the relevant pore phase can be obtained and maintained during the manufacturing process through appropriate process control.

In some specific embodiments, the fluorescent ceramic phase 11 is a garnet system. More preferably, the fluorescent ceramic phase 11 is Y ₃ Al ₅ O ₁₂ : Ce or Lu ₃ Al ₅ O ₁₂ : Ce. Y ₃ Al ₅ O ₁₂ : Ce is also based on cerium-activated yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ), also known as YAG: Ce; of course, erbium can also be doped into the YAG structure to slightly change the emitted light (Gd-YAG: Ce). Cerium ions partially absorb blue light (wavelength of about 420-490 nm) emitted by the excitation light source and re-emit yellow light with a broad spectrum of about 570 nm. In some embodiments, the combination of the blue light not involved in the excitation and the yellow light emitted after the excitation provides the required white light. In the same way, Lu ₃ Al ₅ O ₁₂ : Ce, which is also based on cerium-activated hafnium aluminum garnet (Lu ₃ Al ₅ O ₁₂ ), is also called LuAG: Ce, which has similar characteristics to YAG: Ce. More details.

Preferably, the pore phase 12 is at least one of a spherical hole, an oval hole, or an elongated hole. It should be noted that the shape of the pore phase 12 is generally spherical, which is related to the sintering temperature and time during the preparation process. In fact, the actual experimental results show that the pore phases located inside the ceramic grains are more likely to form spherical or oval holes; while the pore phases located at the grain boundaries are more likely to have elongated holes.

The invention introduces the pore phase into the inside of the crystal grains of the fluorescent ceramic, and when the pore phase is located in the crystal grains, it is beneficial to the improvement of the mechanical properties and the light efficiency of the ceramic itself. Its light efficiency is improved; on the other hand, the introduction of the pore phase into the grains avoids the introduction of defects when the pore phase is located at the grain boundaries of the ceramic grains, which can prevent the ceramics from breaking along the grain boundaries, and improves the mechanical properties of the fluorescent ceramics.

Therefore, when the fluorescent ceramic of the present invention is applied to a light source device, the light conversion efficiency and mechanical properties of the fluorescent ceramic can also be improved when the pore phase inside the crystal grains can improve light uniformity.

The second aspect of the present invention also provides a light source device. As shown in FIG. 3, the light source device includes an excitation light source 2 and any of the porous fluorescent ceramics 1 described above. The excitation light source 2 can emit excitation light for exciting the porous structure. The fluorescent ceramic 1 emits excited light.

It can be understood that, generally speaking, the excitation light source emits light with a shorter wavelength, such as ultraviolet light, blue light, and the like. The type of the excitation light source may be at least one of an LED (Light Emitting Diode, light emitting diode) or an LD laser diode (Laser diode, laser diode). Of course, other types of existing light sources can also be used as the excitation light source.

It should be noted that, in different application scenarios, the setting manner of the light source device may be slightly different. In a specific embodiment, the porous fluorescent ceramic 1 is directly attached to the blue LED light emitting chip, and the porous fluorescent ceramic is selected from YAG: Ce. In this embodiment, the light source device is a white light LED light source. The blue light emitted by the blue LED light emitting chip excites the porous fluorescent ceramic on the one hand to obtain a broad spectrum of yellow light, and on the other hand, the unexcited blue light and yellow light are mixed to obtain white light. .

In other embodiments, the porous fluorescent ceramic 1 can be excited by a blue light LD (laser diode). Since the laser diode has a very high brightness, the light source device receiving the laser light with high brightness is excited by the blue light laser diode. Therefore, the above-mentioned light source device can be applied to the field of projection display.

A third aspect of the present invention also provides a projection device including: the light source device described above; a light modulation device that modulates light from the light source device according to image information to form image light; and projection optics System, the projection optical system projects the image light.

The fourth aspect of the present invention also provides a method for preparing a porous fluorescent ceramic.

In some embodiments, the porous fluorescent ceramics are prepared by wet mixing, tablet molding and atmosphere sintering. The specific preparation process is as follows:

S1: mixing of raw materials,

The oxide raw material is weighed according to the stoichiometric ratio of the fluorescent ceramic, and the particle size of the oxide raw material is 1 to 1000 nm, and then an adhesive, a sintering aid and a solvent are added, and the raw material powder is obtained by ball milling for 8 to 24 hours;

S2: compression molding,

The raw material powder obtained in S1 is sieved, pre-pressed, and then cold isostatically compacted at 100 to 300 MPa to obtain a ceramic green body;

S3: pre-sintering excludes organics,

Pre-sintering the ceramic green body obtained from S3 in a temperature range of 600-1000 ° C for 4-10 hours to exclude organic matter;

S4: ceramic sintering,

The ceramic green body obtained by S3 is sintered in an inert atmosphere to obtain a fluorescent ceramic. The sintering time is 6 to 10 hours, the sintering temperature is 1550 to 1800 ° C, and the heating rate is 10 to 20 ° C / min.

Example one

In this embodiment, the porous fluorescent ceramics are prepared by wet mixing, tabletting and atmosphere sintering. The specific preparation process is as follows:

S1: raw material mixing

The oxide raw materials are accurately weighed according to the stoichiometric ratio. In this embodiment, yttrium oxide (Y ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), and cerium oxide (CeO ₂ ) are specifically mentioned. Among them, Ce ^{3+ in the} luminescent ceramics The ion concentration is 0.1 to 0.5%, preferably 0.2 to 0.4%. In this embodiment, the cerium oxide (CeO ₂ ) raw material is weighed according to a 0.3% metering ratio. It should be noted that the raw materials are yttrium oxide, cerium oxide, and alumina. The particle diameters of the particles are all in the nanometer range of 1 to 1000 nm. The particle diameters of yttrium oxide and cerium oxide are preferably 20 to 50 nm, and the particle diameters of alumina are preferably 100 to 300 nm. The selection of the particle size of the raw materials is very important for controlling the distribution of the pore phase in the fluorescent ceramic phase, and directly affects the size of the pore phase and the proportion of the proportion inside the crystal grains.

Add the adhesive, sintering aid and a certain amount of solvent after weighing the oxide raw materials;

In this embodiment, the adhesive is PVB, the content of which is 2 to 5%; the sintering aid is TEOS, whose content is 0.2 to 0.5%; the solvent is anhydrous ethanol, and the amount is preferably to completely disperse the above raw materials. It is not specifically limited here.

In addition, dispersants such as PEG, CTAB, and SDS can be optionally added.

The ball milling time is 8 to 24 hours, preferably 14 to 18 hours. After mixing, the slurry is poured out into a drying box for drying.

S2: Press molding

Sieving the uniformly mixed dry powder obtained from S1 to reduce physical agglomeration, weighing a certain amount of powder for tableting treatment; specifically, in this embodiment, first, uniaxial tabletting of 10-30 MPa is used for molding, and then A 100-300Mpa cold isostatic compaction is performed to obtain a ceramic green body.

S3: Pre-sintering excludes organics

The ceramic green body obtained by S3 is sintered in a temperature range of 600 to 1000 ° C. for 4 to 10 hours to remove organic substances such as adhesives and dispersants in the green body. In this embodiment, the specific temperature is 1000 ° C., and the sintering time is 4 hours. In other embodiments, a lower temperature can be used for a longer time, such as a temperature of 600 degrees Celsius, and the sintering time is 10 hours.

S4: Ceramic sintering

The ceramic green body obtained by S3 is sintered in an inert atmosphere to obtain a fluorescent ceramic. In this embodiment, sintering is performed in a nitrogen atmosphere. The sintering time is 6 to 10 hours, the sintering temperature is 1550 to 1800 ° C, and the heating rate is 10 ～ 20 ℃ / min, the size and porosity of pores can be controlled by controlling the sintering time and sintering temperature. It can be understood that the inert atmosphere may also include Ar and the like.

It should be noted that by controlling the particle size of the raw materials and the heating process, the state of the stomata phase in the ceramic can be achieved, and the state of the stomata phase in the ceramic grains can be achieved, which affects the mechanical properties of the ceramic (ceramics are more likely to fracture along the grain boundary ) Important factor.

The microstructure of the porous fluorescent ceramic (sample # 1) prepared by using this embodiment is shown in FIGS. 4 and 5.

As shown in Figure 4 and Figure 5, the ceramic grain size of sample No. 1 is about 10-20um, the pore phase is closed pores, the size of the pore phase is 0.5-1.5um, and the porosity is 3-5%. Among them, the number of the pore phases 121 in the crystal grains 111 of the fluorescent ceramic phase is much larger than that of the pore phases 122 in the grain boundaries 121, and the pore phases 121 in the crystal grains 111 of the fluorescent ceramic phase are circular or oval.

Comparative Example One

Based on Example 1, 2 # sample of Comparative Example 1 was prepared by changing part of the raw materials and related parameters. The specific preparation process is as follows:

S1: raw material mixing

Accurately weigh yttrium oxide (Y ₂ O ₃ ), alumina (Al ₂ O ₃ ), and cerium oxide (CeO ₂ ) according to the stoichiometric ratio. The particle size of cerium oxide (CeO ₂ ) is 20-50 nm, and yttrium oxide The particle size of the aluminum oxide is 200 to 300 nm, and the particle size of the aluminum oxide is 1 to 2 um. Then add an adhesive, a sintering aid, and a certain amount of a solvent, the amount of which is the same as that of the first embodiment;

S2: Press molding

Sieving the uniformly mixed dry powder obtained from S1 to reduce physical agglomeration, weighing a certain amount of powder for tableting treatment; specifically, in this embodiment, first, uniaxial tabletting of 10-30 MPa is used for molding, and then A 100-300Mpa cold isostatic compaction is performed to obtain a ceramic green body.

S3: Pre-sintering excludes organics

The ceramic green body obtained by S3 is sintered in a temperature range of 600 to 1000 ° C. for 4 to 10 hours to remove organic substances such as adhesives and dispersants in the green body. The specific temperature of this comparative example is 1000 ° C, and the sintering time is 4 hours.

S3: Pre-sintering excludes organics

The ceramic green body obtained by S3 is sintered in a temperature range of 600 to 1000 ° C. for 4 to 10 hours to remove organic substances such as adhesives and dispersants in the green body. The specific temperature of this comparative example is 1000 ° C, and the sintering time is 4 hours.

S4: Ceramic sintering

The ceramic green body obtained from S3 is sintered in an inert atmosphere to obtain a fluorescent ceramic. In this embodiment, sintering is performed in a nitrogen atmosphere. The sintering time is 4-6 hours, the sintering temperature is 1550-1800 ° C, and the heating rate is 5 ~ 8 ° C / min.

The ceramic grain size of the 2 # sample is 2-10um. The pore phase exists completely between the grain boundaries. The pore phase has a size of 0.2 to 2 um, and the porosity is 3 to 5%.

Contrast tests were performed on samples # 1 and # 2. The mechanical properties of No. 1 sample are stronger than those of No. 2 sample; and, a blue laser is used to irradiate the sample at a power of 2.4 W and obtain its luminous flux.

As shown in Table 1:

Table 1

Sample serial number	Blue light power (w)	Lumen (lm)	CIE_x		CIE_y
1#	2.4	508	0.3984	0.5201
2#	2.4	476	0.3957	0.5162

As shown in Table 1, under the condition of the same excitation power, the sample No. 1 # has a higher luminous flux, that is, the porous fluorescent ceramic prepared by the present invention has a higher luminous efficiency.

It should be noted that, in this article, the terms "including", "including" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, It also includes other elements not explicitly listed, or elements inherent to such a process, method, article, or system. Without more restrictions, an element limited by the sentence "including a ..." does not exclude the existence of other identical elements in the process, method, article, or system that includes the element.

The sequence numbers of the foregoing embodiments of the present invention are only for description, and do not represent the superiority or inferiority of the embodiments.

The above are only preferred embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description and drawings of the present invention, or directly or indirectly used in other related technical fields All are included in the patent protection scope of the present invention.

Claims (9)

1. A porous fluorescent ceramic includes a fluorescent ceramic phase and a pore phase dispersed in the fluorescent ceramic phase, and is characterized in that at least a part of the pore phase is located in crystal grains of the fluorescent ceramic phase. 2. The porous fluorescent ceramic according to claim 1, wherein the size of the crystal grains of the fluorescent ceramic phase is 10-20um.
2. The porous fluorescent ceramic according to claim 1, wherein the size of the pore phase is 0.5 to 1.5 um.
3. The porous fluorescent ceramic according to claim 1, wherein a porosity of the porous fluorescent ceramic is 1% to 10%.
4. The porous fluorescent ceramic according to claim 1, wherein the fluorescent ceramic phase is a garnet system.
5. The porous fluorescent ceramic according to claim 1, wherein the pore phase is at least one of a spherical hole, an oval hole, or an elongated hole.
6. A light source device, comprising an excitation light source and the porous fluorescent ceramic according to any one of claims 1 to 7, wherein the excitation light source is capable of emitting excitation light for exciting the porous fluorescent ceramic to emit excited light.
7. A projection device, comprising:

   The light source device according to claim 7;

   A light modulation device that modulates light from the light source device according to image information to form image light; and

   A projection optical system that projects the image light.
8. A method for preparing a porous fluorescent ceramic is characterized in that it includes the following steps:

   S1: mixing of raw materials,

   The oxide raw material is weighed according to the stoichiometric ratio of the fluorescent ceramic, and the particle size of the oxide raw material is 1 to 1000 nm, and then an adhesive, a sintering aid and a solvent are added, and the raw material powder is obtained by ball milling for 8 to 24 hours;

   S2: compression molding,

   The raw material powder obtained in S1 is sieved, pre-pressed, and then cold isostatically compacted at 100 to 300 MPa to obtain a ceramic green body;

   S3: pre-sintering excludes organics,

   Pre-sintering the ceramic green body obtained from S3 in a temperature range of 600-1000 ° C for 4-10 hours to exclude organic matter;

   S4: ceramic sintering,

   The ceramic green body obtained by S3 is sintered in an inert atmosphere to obtain a fluorescent ceramic. The sintering time is 6 to 10 hours, the sintering temperature is 1550 to 1800 ° C, and the heating rate is 10 to 20 ° C / min.
9. The preparation method according to claim 9, wherein the oxide raw material comprises yttrium oxide, cerium oxide, and alumina;

   The particle diameter of the yttrium oxide and cerium oxide is 20-50 nm;

   The particle diameter of the alumina is 100-300 nm.

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