CN115215646B - High thermal conductivity and high thermal stability three-phase fluorescent ceramic for laser lighting and preparation method thereof - Google Patents

Abstract

The invention discloses a three-phase fluorescent ceramic with high thermal conductivity and high thermal stability for laser lighting and a preparation method thereof. Ce:LuAG powder and MgO powder are used as ceramic raw material powders and prepared by a discharge plasma sintering method. The three-phase fluorescent ceramic is Ce:LuAG‑MgAl ₂ O ₄ ‑MgO, Ce:LuAG is used as the ceramic body, MgAl ₂ O ₄ and MgO are both high thermal conductivity phases, and when excited by a blue LD chip with a wavelength near 455nm, emits High-brightness broadband yellow light around 550nm, thermal conductivity 28Wm ^‑1 K ^‑1 ~ 32Wm ^‑1 K ^‑1 , the emission intensity only loses 1.4% to 3.4% at 150°C, and only 3.2% at 250°C % to 5.8%, has high thermal conductivity and high thermal stability, and the preparation method is simple, the time is short, the sintering temperature is low, and it can be applied to high-power LED/LDs devices.

Description

A three-phase fluorescent ceramic with high thermal conductivity and high thermal stability for laser lighting and its preparation method

technical field

The invention relates to the technical field of fluorescent ceramics, in particular to a three-phase fluorescent ceramic with high thermal conductivity and high thermal stability for laser lighting and a preparation method thereof.

Background technique

The way to generate white light is to combine blue light-emitting diodes and yellow fluorescent conversion materials (YAG:Ce). Due to high-power laser irradiation, in order to obtain a good heat dissipation effect, the fluorescence conversion material must have good thermal properties, and garnet-based composite ceramic phosphors have thus received extensive attention. By adding high thermal conductivity phases, such as Al ₂ O ₃ (32-35W m ^-1 K ^-1 ), MgAl ₂ O ₄ (22W m ^-1 K ^-1 ), MgO (47.2W m ^-1 K ^-1 -53.5W The high thermal conductivity of m ^-1 K ^-1 ) can improve their thermal performance, and the complex phase can also act as a scattering center by changing the direction of light propagation in the ceramic, thereby increasing the light absorption. The complex phase with lower refractive index compared to the main phase can also improve the light extraction efficiency by reducing the reflection loss of the emitted light. Lu ₃ Al ₅ O ₁₂ :Ce ³⁺ (LuAG:Ce) is obviously superior to other fluorescent conversion materials in terms of thermal quenching, coupled with the good thermal conductivity of ceramics, it is very suitable as a matrix material for laser lighting and display.

In terms of using LuAG as a matrix material to prepare composite ceramics, CN109896852A discloses a composite fluorescent ceramic for white light illumination excited by blue light, a preparation method and a light source device. The composite fluorescent ceramic used for white light illumination excited by blue light has lutetium Aluminum garnet fluorescent phase and Al ₂ O ₃ high thermal conductivity phase, but the preparation method takes a long time, has many preparation steps, and relatively high sintering temperature, which limits its application in high-power LED/LDs devices.

Contents of the invention

One of the objects of the present invention is to provide a method for preparing a three-phase fluorescent ceramic with high thermal conductivity and high thermal stability for laser lighting, which has simple steps, low sintering temperature and short time.

The second object of the present invention is to provide a three-phase fluorescent ceramic with high thermal conductivity and high thermal stability for laser lighting prepared by the above preparation method.

To achieve the above object, the technical scheme adopted in the present invention is as follows:

In the first aspect, the present invention provides a method for preparing a three-phase fluorescent ceramic with high thermal conductivity and high thermal stability for laser lighting, comprising the following steps:

(1) Take Ce:LuAG powder and MgO powder respectively by mass ratio as ceramic raw material powder, wherein MgO accounts for 20% to 50% of the total mass of ceramic raw material powder;

(2) After blending Ce:LuAG and MgO, add absolute ethanol, and ball mill to fully mix;

(3) The slurry obtained after ball milling is taken out and dried to obtain dry powder;

(4) Wrap the dried powder with graphite paper, conduct discharge plasma sintering in a vacuum state, and cool to room temperature to obtain three-phase fluorescent ceramics.

Preferably, the particle size of the Ce:LuAG powder in step (1) is 1 μm-1.3 μm, the particle size of the MgO powder is 1.5 μm-2 μm, and the purity is above 99.99%.

Preferably, the sintering pressure of the spark plasma sintering in step (4) is 50-100 MPa, the pulse current is 200-400A, the heat preservation sintering time is 20-50 min, and the sintering temperature is 1480°C-1600°C.

Preferably, the ball milling speed in step (2) is 180-250 rpm, and the ball milling time is 15-30 hours.

Preferably, the drying temperature in step (2) is 70-90° C., and the drying time is 8-12 hours.

In the second aspect, the present invention provides a three-phase fluorescent ceramic with high thermal conductivity and high thermal stability for laser lighting prepared by the above preparation method, the three-phase fluorescent ceramic is Ce:LuAG-MgAl ₂ O ₄ -MgO, and Ce:LuAG is used as the ceramic The host, MgAl ₂ O ₄ and MgO are all high thermal conductivity phases.

The fluorescent ceramic emits a high-brightness broadband yellow light near 550nm when excited by a blue light LD chip with a wavelength near 455nm, and has a thermal conductivity of 28Wm ^-1 K ^-1 ~ 32Wm ^-1 K ^-1 . The intensity only loses 1.4% to 3.4%, and the emission intensity only loses 3.2% to 5.8% at 250°C.

The multi-phase ceramic material prepared by the present invention adopts Ce:LuAG as the main phase, and the addition of excess MgO acts as a sintering aid while reacting with part of LuAG at a specific temperature to generate MgAl ₂ O ₄ and Lu ₂ O ₃ . In , a very small part of MgAl ₂ O ₄ and Lu ₂ O ₃ reacted again to generate Lu(Al,Mg)O ₃ , and most of MgAl ₂ O ₄ and MgO acted as a complex phase of LuAG. By adjusting the content of MgO, the significant While improving the thermal conductivity, the light scattering effect and the light absorption rate are effectively enhanced.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The three-phase ceramic prepared by the present invention emits high-brightness broadband yellow light around 550 nm when excited by a blue light LD chip with a wavelength around 455 nm.

(2) The present invention makes full use of the advantages of excessively adding MgO, and reacts with LuAG to generate MgAl ₂ O ₄ and MgO together as a complex phase of LuAG while serving as a sintering aid, which significantly improves its thermal conductivity and thermal stability.

(3) The present invention adopts the three phases of Ce:LuAG-MgAl ₂ O ₄ -MgO, and through the introduction of MgAl ₂ O ₄ and MgO two-phase scattering sources, the utilization rate of blue light is improved and the total reflection (TIR) of fluorescence is eased effect, effectively improving the light extraction rate.

(4) The present invention prepares Ce:LuAG-MgAl ₂ O ₄ -MgO three-phase ceramics with high brightness and high thermal stability by SPS sintering. The preparation method is simple and the time is short. It can be applied to high-power LED/LDs devices, greatly improving The application value of the device is improved.

Description of drawings

Fig. 1 is the XRD diagram of the sample Ce:LuAG-MgAl ₂ O ₄ -MgO prepared in Example 1 of the present invention: (A) the comparison diagram of LuAG, MgO and the sample, (B) the comparison diagram of MgAl ₂ O ₄ and the sample;

Fig. 2 is the EL spectrogram of the sample Ce:LuAG-MgAl ₂ O ₄ -MgO excited by the LD chip at 455nm in Example 1 of the present invention;

Fig. 3 is the variable temperature spectrogram of the sample Ce:LuAG-MgAl ₂ O ₄ -MgO prepared in Example 1 to Example 4 of the present invention, where MgO accounts for 20%-50% of the total mass of Ce:LuAG and MgO;

Fig. 4 is a thermal conductivity diagram of samples Ce:LuAG-MgAl ₂ O ₄ -MgO prepared in Example 1 to Example 4 of the present invention, where MgO accounts for 20%-50% of the total mass of Ce:LuAG and MgO.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

The Ce:LuAG powder and MgO powder used in the following examples are commercially available.

Example 1

According to the chemical formula Ce:LuAG-MgAl ₂ O ₄ -MgO, MgO accounts for 30% of the total mass of Ce:LuAG and MgO. Ce: 42g of LuAG powder, 18g of MgO powder with a purity of 99.99% and a particle size of 1.7 μm. After blending Ce:LuAG and MgO, add absolute ethanol, mix thoroughly by ball milling, and dry the powder obtained after ball milling in an oven at 90°C for 12 hours to obtain a dry powder. Wrap the dry powder with graphite paper and store in a vacuum state Spark plasma sintering was carried out under the following conditions, the sintering pressure was 80MPa, the pulse current was 300A, the heat preservation sintering time was 40min, the sintering temperature was 1550°C, and the three-phase ceramic was obtained after cooling to room temperature.

Under the excitation of the blue light LD chip with a wavelength near 455nm, it emits a high-brightness broadband yellow light near 550nm, with a thermal conductivity of 32Wm ^-1 K ^-1 . The emission intensity only loses 1.4% at 150°C, and emits at 250°C. The strength is only lost by 3.2%.

Example 2

According to the chemical formula Ce:LuAG-MgAl ₂ O ₄ -MgO, MgO accounts for 20% of the total mass of Ce:LuAG and MgO. According to the stoichiometric ratio of the corresponding raw materials, the Ce: 48 g of LuAG powder, 12 g of MgO with a purity of 99.99% and a particle size of 1.7 μm. After blending Ce:LuAG and MgO, add absolute ethanol, mix thoroughly by ball milling, and dry the powder obtained after ball milling in an oven at 90°C for 12 hours to obtain a dry powder. Wrap the dry powder with graphite paper and store in a vacuum state Spark plasma sintering was carried out under the following conditions, the sintering pressure was 80MPa, the pulse current was 300A, the heat preservation sintering time was 40min, the sintering temperature was 1550°C, and the three-phase ceramic was obtained after cooling to room temperature.

Under the excitation of a blue LD chip with a wavelength near 455nm, it emits a high-brightness broadband yellow light near 550nm. The thermal conductivity is 28.8Wm ^-1 K ^-1 , and the emission intensity only loses 3.2% at 150°C, and at 250°C. The emission intensity is only lost by 5.2%.

Example 3

According to the chemical formula Ce:LuAG-MgAl ₂ O ₄ -MgO, MgO accounts for 40% of the total mass of Ce:LuAG and MgO. Ce: 36 g of LuAG, 24 g of MgO with a purity of 99.99% and a particle size of 1.7 μm. After blending Ce:LuAG and MgO, add absolute ethanol, mix thoroughly by ball milling, and dry the powder obtained after ball milling in an oven at 90°C for 12 hours to obtain a dry powder. Wrap the dry powder with graphite paper and store in a vacuum state Spark plasma sintering was carried out under the following conditions, the sintering pressure was 80MPa, the pulse current was 300A, the heat preservation sintering time was 40min, the sintering temperature was 1550°C, and the three-phase ceramic was obtained after cooling to room temperature. Under the excitation of the blue light LD chip with a wavelength near 455nm, it emits high-brightness broadband yellow light near 550nm. The thermal conductivity is 30Wm ^-1 K ^-1 . The emission intensity only loses 2.4% at 150°C, and emits at 250°C The strength is only lost by 3.8%.

Example 4

According to the chemical formula Ce:LuAG-MgAl ₂ O ₄ -MgO, MgO accounts for 50% of the total mass of Ce:LuAG and MgO. According to the stoichiometric ratio of the corresponding raw materials, respectively weigh the Ce: 30 g of LuAG, 30 g of MgO with a purity of 99.99% and a particle diameter of 1.7 μm. After blending Ce:LuAG and MgO, add absolute ethanol, mix thoroughly by ball milling, and dry the powder obtained after ball milling in an oven at 90°C for 12 hours to obtain a dry powder. Wrap the dry powder with graphite paper and store in a vacuum state Spark plasma sintering was carried out under the following conditions, the sintering pressure was 80MPa, the pulse current was 300A, the heat preservation sintering time was 40min, the sintering temperature was 1550°C, and the three-phase ceramic was obtained after cooling to room temperature.

Under the excitation of a blue LD chip with a wavelength near 455nm, it emits a high-brightness broadband yellow light near 550nm, with a thermal conductivity of 28Wm ^-1 K ^-1 . The emission intensity only loses 3.4% at 150°C, and emits at 250°C. The strength is only lost by 5.8%.

Fig. 3 is a temperature-varying spectrum of samples Ce:LuAG-MgAl ₂ O ₄ -MgO prepared in Example 1 to Example 4 of the present invention, where MgO accounts for 20%-50% of the total mass of Ce:LuAG and MgO. It can be seen from FIG. 3 that the emission intensity loss range is between 1.4%-3.4% at 150°C, and the emission intensity loss range is between 3.2%-5.8% at 250°C.

Fig. 4 is a thermal conductivity diagram of samples Ce:LuAG-MgAl ₂ O ₄ -MgO prepared in Example 1 to Example 4 of the present invention, where MgO accounts for 20%-50% of the total mass of Ce:LuAG and MgO. It can be seen from Figure 4 that the thermal conductivity is between 28Wm ^-1 K ^-1 -32Wm ^-1 K ^-1 .

Example 5

According to the chemical formula Ce:LuAG-MgAl ₂ O ₄ -MgO, MgO accounts for 30% of the total mass of Ce:LuAG and MgO. According to the stoichiometric ratio of the corresponding raw materials, respectively weigh Ce with a purity of 99.99% and a particle size of 1 μm : 42 g of LuAG, 18 g of MgO with a purity of 99.99% and a particle diameter of 1.5 μm. After blending Ce:LuAG and MgO, add absolute ethanol, mix thoroughly by ball milling, dry the powder obtained after ball milling in an oven at 70°C for 9 hours to obtain dry powder, wrap the dry powder with graphite paper and store in vacuum state Spark plasma sintering was carried out under the following conditions, the sintering pressure was 50MPa, the pulse current was 200A, the heat preservation sintering time was 50min, the sintering temperature was 1500°C, and the three-phase ceramic was obtained after cooling to room temperature.

Under the excitation of a blue LD chip with a wavelength near 455nm, it emits a high-brightness broadband yellow light near 550nm. The thermal conductivity is 29.7Wm ^-1 K ^-1 , and the emission intensity only loses 2.1% at 150°C, and at 250°C. The emission intensity is only lost by 4%.

Example 6

According to the chemical formula Ce:LuAG-MgAl ₂ O ₄ -MgO, MgO accounts for 30% of the total mass of Ce:LuAG and MgO. Ce: 42 g of LuAG, 18 g of MgO with a purity of 99.99% and a particle diameter of 2 μm. After blending Ce:LuAG and MgO, add absolute ethanol, mix thoroughly by ball milling, and dry the powder obtained after ball milling in an oven at 80°C for 9 hours to obtain a dry powder. Spark plasma sintering was carried out at 100MPa sintering pressure, 400A pulse current, 20min heat preservation sintering time, 1480℃ sintering temperature, and three-phase ceramics were obtained after cooling to room temperature.

Under the excitation of a blue LD chip with a wavelength near 455nm, it emits a high-brightness broadband yellow light near 550nm, with a thermal conductivity of 30.2Wm ^-1 K ^-1 , and the emission intensity only loses 1.8% at 150°C, and at 250°C The emission intensity is only lost by 3.7%.

Example 7

According to the chemical formula Ce:LuAG-MgAl ₂ O ₄ -MgO, MgO accounts for 30% of the total mass of Ce:LuAG and MgO. Ce: 42 g of LuAG, 18 g of MgO with a purity of 99.99% and a particle diameter of 1.8 μm. After blending Ce:LuAG and MgO, add absolute ethanol, mix thoroughly by ball milling, and dry the powder obtained after ball milling in an oven at 90°C for 12 hours to obtain a dry powder. Wrap the dry powder with graphite paper and store in a vacuum state Spark plasma sintering was carried out under the following conditions, the sintering pressure was 80MPa, the pulse current was 300A, the heat preservation sintering time was 40min, the sintering temperature was 1580°C, and the three-phase ceramic was obtained after cooling to room temperature.

Under the excitation of a blue LD chip with a wavelength near 455nm, it emits a high-brightness broadband yellow light near 550nm, with a thermal conductivity of 29.8Wm ^-1 K ^-1 , and the emission intensity only loses 1.6% at 150°C, and at 250°C The emission intensity is only lost by 3.2%.

Example 8

According to the chemical formula Ce:LuAG-MgAl ₂ O ₄ -MgO, MgO accounts for 30% of the total mass of Ce:LuAG and MgO. 42 g of Ce:LuAG, 18 g of MgO with a purity of 99.99% and a particle size of 1.5 μm, the particle size of Ce:LuAG is 1.1 μm, and the particle size of MgO is 1.5 μm. After blending Ce:LuAG and MgO, add absolute ethanol, mix thoroughly by ball milling, and dry the powder obtained after ball milling in an oven at 90°C for 12 hours to obtain a dry powder. Wrap the dry powder with graphite paper and store in a vacuum state Spark plasma sintering was carried out under the following conditions, the sintering pressure was 80MPa, the pulse current was 300A, the heat preservation sintering time was 40min, the sintering temperature was 1600°C, and the three-phase ceramic was obtained after cooling to room temperature.

Under the excitation of a blue LD chip with a wavelength near 455nm, it emits a high-brightness broadband yellow light near 550nm, with a thermal conductivity of 30.3Wm ^-1 K ^-1 , and the emission intensity only loses 1.8% at 150°C, and at 250°C The emission intensity is only lost by 3.4%.

The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Anyone familiar with the technical field within the technical scope disclosed in the present invention, whoever is within the spirit and principles of the present invention Any modifications, equivalent replacements and improvements made within shall fall within the protection scope of the present invention.

Claims (4)

1. The preparation method of the three-phase fluorescent ceramic with high heat conduction and high thermal stability for laser illumination is characterized by comprising the following steps of:

(1) Respectively weighing Ce, luAG powder and MgO powder according to the mass ratio, wherein MgO accounts for 20% -50% of the total mass of the ceramic raw material powder; the grain diameter of the powder of LuAG is 1-1.3 mu m, the grain diameter of the powder of MgO is 1.5-2 mu m, and the purity is over 99.99 percent;

(2) Mixing Ce, luAG and MgO, adding absolute ethyl alcohol, and fully mixing by ball milling;

(3) Taking out the slurry obtained after ball milling, and drying to obtain dry powder;

(4) Wrapping the dried powder with graphite paper, performing spark plasma sintering in a vacuum state, and cooling to room temperature to obtain three-phase fluorescent ceramic; the sintering pressure of the spark plasma sintering is 50-100 MPa, the pulse current is 200-400A, the heat preservation sintering time is 20-50 min, and the sintering temperature is 1480-1600 ℃;

the three-phase fluorescent ceramic is Ce, luAG-MgAl ₂ O ₄ MgO, ce, luAG as ceramic body, mgAl ₂ O ₄ And MgO are both high thermal conductivity phases.

2. The method for preparing the three-phase fluorescent ceramic with high heat conductivity and high thermal stability for laser illumination according to claim 1, wherein the ball milling rotating speed in the step (2) is 180-250 rpm, and the ball milling time is 15-30 h.

3. The method for preparing the three-phase fluorescent ceramic with high heat conductivity and high thermal stability for laser illumination according to claim 1, wherein the temperature of drying in the step (3) is 70-90 ℃ and the drying time is 8-12 h.

4. A high thermal conductivity and high thermal stability three-phase fluorescent ceramic for laser illumination produced by the production method according to any one of claims 1 to 3.