CN112159220B - High-thermal-stability high-quantum-efficiency fluorescent ceramic for white light LED/LD and preparation method thereof - Google Patents
High-thermal-stability high-quantum-efficiency fluorescent ceramic for white light LED/LD and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a high-thermal-stability high-quantum-efficiency fluorescent ceramic for a white light LED/LD and a preparation method thereof, wherein the chemical formula of the fluorescent ceramic is as follows: (Y) y Ce z Lu 1‑z‑y ) 3 (Sc x Al 1‑x ) 2 Al 3 O 12 Wherein, in the step (A),xis Sc 3+ Doped octahedral Al 3+ The mole percentage of the sites is,yis Y 3+ Doped Lu 3+ The mole percentage of the sites is,zis Ce 3+ Doped Lu 3+ Mole percent of the sites, 0.5<x≤0.8，0.4≤y≤0.6，y：x=2：3~3：4，0<z is less than or equal to 0.015, and the material is prepared by sintering by a solid-phase reaction method. The fluorescent ceramic provided by the invention realizes the light emission from green light to green yellow, the color temperature is 4000-10000K, the luminous intensity is attenuated by 2-5% at 150 ℃, and the internal quantum efficiency is 82-88%. The prepared ceramic has simple process and is easy for industrial production.
Description
Technical Field
The invention relates to the technical field of fluorescent ceramics, in particular to high-thermal-stability high-quantum-efficiency fluorescent ceramic for a white light LED/LD and a preparation method thereof.
Background
Fluorescent conversion white light emitting diodes and laser diodes (abbreviated as LEDs/LDs) are widely used as solid-state illumination light sources for new generation, because of their advantages of high luminous efficiency, good robustness, small device size, long service life, and so on. With the updating of the technology, the fluorescent powder Ce is used 3+ :Y 3 Al 5 O 12 The traditional mode of mixing (Ce: YAG for short) and organic silica gel is gradually replaced by a remote excitation packaging mode of an excitation source and Ce: YAG fluorescent ceramic. YAG fluorescent ceramic has become a hot point of domestic and foreign research due to the advantages of high heat conductivity coefficient, good mechanical property, stable physical and chemical properties, easy realization of high doping concentration and the like. YAG fluorescent ceramics, however, have significant disadvantages under blue LED/LD excitation, such as: the color proportion of the emitted light is disordered, the improved thermal quenching temperature is low, the quantum efficiency is low and the like, so that the prepared packaged device has the defects of low color rendering index, high relative color temperature, low luminous efficiency and the like, and the high-power use requirement is difficult to meet.
YAG fluorescent ceramic is reported to regulate the light emitting behavior and the spectral emission peak. However, when the performance of the emission spectrum is regulated, the thermal stability and quantum efficiency of the fluorescent ceramic are reduced. The quantum efficiency is far less than that of the original substrate, and the luminous intensity is mostly reduced to below 50% in a normal service temperature environment. At present, the method for regulating and controlling the spectrum of the fluorescent ceramic at home and abroad is mainly divided into Mg 2+ -Si 4+ Ion pairs are replaced (J.Mater.chem.C., 2018,6,12200-12205.J.Mater.chem.C,2016,4, 2359-2366.), red light ions are added (J.Eur.Ceram.Soc., 2017,37 (10), 3403-3409.), the full width at half maximum of an emission spectrum is increased by regulating energy levels (ACS appl.Mater.Interfaces,2019,11 (2), 2130-2139.), and the composite structure realizes red, green and yellow three-color coupled luminescence (CN 110218085A). The above method, although capable of improving individual luminescenceCan be used. However, the disadvantages are also obvious, the concentration of the added external ions for generating the pure garnet phase is difficult to control accurately, and a heterogeneous phase is generated, so that the thermal stability and the quantum efficiency of the corresponding fluorescent ceramic are both reduced remarkably.
Disclosure of Invention
The invention aims to provide a high-thermal-stability high-quantum-efficiency fluorescent ceramic for a white light LED/LD, which has high thermal stability and high quantum efficiency.
The invention also aims to provide a preparation method of the high-thermal stability quantum efficiency fluorescent ceramic for the white light LED/LD, which is easy for industrial production.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a high-thermal-stability high-quantum-efficiency fluorescent ceramic for white light LEDs/LDs has a chemical formula as follows:
(Y y Ce z Lu 1-z-y ) 3 (Sc x Al 1-x ) 2 Al 3 O 12
wherein x is Sc 3+ Doped octahedral Al 3+ Mole percent of the site, Y is Y 3+ Doped Lu 3+ Mole percent of the sites, z being Ce 3+ Doped Lu 3+ Mole percent of the sites, 0.5<x≤0.8，0.4≤y≤0.6，y：x＝2： 3～3：4，0<z≤0.015。
Under the excitation of high-power blue light LED (350-500 mA) or blue light LD (2W-10W), the green-green light to green-yellow light emission is realized, the color temperature is 4000-10000K, the reduction of the luminous intensity along with the temperature rise is not obvious along with the operation of the device, the luminous intensity is attenuated by 2-5% at 150 ℃, and the thermal stability is excellent. The quantum efficiency in the ceramic is between 82% and 88%.
The invention also provides a preparation method of the fluorescent ceramic with high thermal stability and high quantum efficiency for the white light LED/LD, which adopts a solid-phase reaction method for sintering and specifically comprises the following steps:
(1) According to the formula (Y) y Ce z Lu 1-z-y ) 3 (Sc x Al 1-x ) 2 Al 3 O 12 ，0.5<x≤0.8，0.4≤y≤0.6， y：x＝2：3～3：4，0<z is less than or equal to 0.015, and alpha-alumina, yttrium oxide, lutetium oxide, scandium oxide and cerium oxide are respectively weighed as raw material powder according to the stoichiometric ratio of the elements; mixing and ball-milling raw material powder and a ball-milling medium according to a certain proportion to obtain mixed slurry;
(2) Placing the mixed slurry obtained in the step (1) in a drying oven for drying, and sieving the dried mixed powder;
(3) Placing the powder sieved in the step (2) into a grinding tool for forming, and then carrying out cold isostatic pressing to obtain a biscuit with the relative density of 51-52%;
(4) Sintering the biscuit obtained in the step (3) in a vacuum furnace at the sintering temperature of 1680-1750 ℃ for 6-10 h, wherein the sintering vacuum degree is not lower than 10 -4 Pa, obtaining fluorescent ceramic;
(5) And (3) carrying out air annealing treatment on the fluorescent ceramic subjected to vacuum sintering in the step (4), wherein the annealing temperature is 1000-1150 ℃, and the heat preservation time is 20-50 h, so as to obtain the fluorescent ceramic with the relative density of 99.2-99.9%.
Preferably, in the step (1), the ball-to-feed ratio is 3.5-4.5: 1, the diameter of the selected grinding ball is 0.5 cm-2 cm.
Preferably, in the step (1), the ball milling rotation speed is 170r/min to 190r/min, and the ball milling time is 25h to 40h.
Preferably, in the step (1), the ball milling medium is absolute ethyl alcohol, and the mass-to-volume ratio of the raw material powder to the ball milling medium is 2-3: 1g/ml.
Preferably, in the step (2), the drying time is 10-15 h, and the drying temperature is 60-70 ℃.
Preferably, in the step (2), the mesh number of the sieved screen is 50-150 meshes, and the sieving frequency is 4-6 times.
Preferably, in the step (4), the temperature rise rate in the vacuum sintering stage is 0.25-0.5 ℃/min, and the temperature fall rate after sintering is 2-4 ℃/min.
Preferably, in the step (4), the temperature rise rate in the air annealing stage is 0.25-0.5 ℃/min, and the temperature drop rate is 2-4 ℃/min.
Compared with the prior art, the invention has the following beneficial effects:
1. the fluorescent ceramic provided by the invention is based on Ce: luAG, using Sc 3+ Ion substituted octahedral Al 3+ Ion site and Y 3+ Ion-substituted dodecahedron Lu 3+ The concept of ions, fully utilizes Sc in octahedral lattice positions 3+ Ions and Al 3+ New effective ionic radius of ion formation and the lattice position Y of dodecahedron 3+ Ion sum Lu 3+ The matching effect of the new effective ionic radius of ion formation. On the basis of regulating the micro-coordination structure of the system, the structural rigidity of the system is provided, and further the Ce is improved 3+ The ion luminescence thermal stability, and the ceramic also has higher quantum efficiency. Sc of introduced octahedral sites 3+ Y of each position of ion and dodecahedron 3+ The ions can promote Ce 3+ The coordination complexity of the crystal field environment of the ions is further changed, the full width at half maximum and the position of the peak of the emission spectrum are further changed, and the color of the emitted light can be adjusted.
2. The method combines a solid-phase reaction method with a vacuum sintering technology, and controls the chemical proportion to ensure that the Sc is in a certain proportion 3+ Ions occupying octahedral Al only 3+ Ion site, Y 3+ Ion occupying only dodecahedral Lu 3+ And (4) ion lattice sites. The ionic radius of the whole system is matched properly, and the garnet pure-phase fluorescent ceramic is obtained.
3. The fluorescent ceramic provided by the invention can effectively solve the problems that Ce: the YAG fluorescent ceramic has the problems of insufficient green light and the preparation of lutetium aluminum garnet pure phase under high Sc content, and can effectively improve the luminous performance of the LED/LD device. Under the excitation of high-power blue light LED (350-500 mA) or blue light LD (2W-10W), the emission spectrum has a main peak between 520 nm and 550nm and a half-height width between 90 nm and 110nm, so that the light emission from green light to green-yellow light is realized, and the color temperature is 4000-10000K.
4. The fluorescent ceramic provided by the invention has the advantages that the luminous intensity is attenuated by 2-5% at 150 ℃, and the internal quantum efficiency is 82-88%.
Drawings
FIG. 1 is a diagram of a fluorescent ceramic prepared according to examples 1 and 2 of the present invention;
FIG. 2 is an XRD pattern of a fluorescent ceramic obtained according to examples 1 and 2 of the present invention and a comparative example;
FIG. 3 is a SEM image of the surface of a fluorescent ceramic prepared in example 1 of the present invention;
FIG. 4 is an emission spectrum of a fluorescent ceramic obtained in example 1 of the present invention under excitation at a wavelength of 460 nm;
FIG. 5 shows the electroluminescence spectrum of the fluorescent ceramic prepared in example 1 under the excitation of a 460nm blue LED chip (I =350 mA);
FIG. 6 is a graph showing a spectrum of emitted light of a fluorescent ceramic according to the temperature variation obtained in example 1 of the present invention;
FIG. 7 is an emission spectrum of a fluorescent ceramic prepared in example 2 of the present invention under excitation at a wavelength of 460 nm;
FIG. 8 shows the electroluminescence spectrum of the fluorescent ceramic prepared in example 2 under the excitation of a 460nm blue LED chip (I =350 mA);
FIG. 9 is a graph showing the transmittance of the fluorescent ceramics obtained in examples 1 and 2 of the present invention and comparative example;
FIG. 10 is a schematic representation of a fluorescent ceramic according to a comparative example of the present invention;
FIG. 11 is an SEM image of the surface of a fluorescent ceramic prepared by a comparative example of the present invention.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
The raw material powder used in the following examples is a commercial product, the purity is more than 99.9%, and the average grain diameter of the alpha-phase alumina is 150 nm-200 nm; the average grain size of the yttrium oxide is 10 nm-50 nm; the average grain diameter of the lutetium oxide is 10nm to 50nm; the average grain diameter of the scandium oxide is 1 nm-50 nm; the average grain diameter of the cerium oxide is 1 nm-50 nm.
Example 1: the preparation chemical formula is (Lu) 0.596 Y 0.4 Ce 0.004 ) 3 (Al 0.4 Sc 0.6 ) 2 Al 3 O 12 Fluorescent ceramic
(1) The target product mass is set to be 60g according to the chemical formula (Lu) 0.594 Y 0.4 Ce 0.006 ) 3 (Al 0.2 Sc 0.8 ) 2 Al 3 O 12 Weighing alpha-alumina (15.25 g), yttrium oxide (10.55 g), lutetium oxide (27.73 g), scandium oxide (6.40 g) and cerium oxide (0.16 g) as raw material powder according to the stoichiometric ratio of the elements; mixing the raw material powder with 120ml of absolute ethyl alcohol, adding 210g of alumina balls with the diameter of 0.5mm, and carrying out ball milling in an alumina ball milling tank, wherein the ball milling speed is 170r/min, and the ball milling time is 40h;
(2) And (2) placing the mixed slurry subjected to ball milling in the step (1) into a 60 ℃ forced air drying oven for drying for 10 hours, and sieving the dried mixed powder with a 50-mesh sieve for 6 times.
(3) Putting the calcined powder in the step (2) into a grinding tool for dry pressing and molding, and then carrying out cold isostatic pressing molding, wherein the relative density of the molded biscuit is 51%;
(4) Sintering the ceramic biscuit obtained in the step (4) in a vacuum furnace, wherein the sintering temperature is 1680 ℃, the heat preservation time is 10 hours, the heating rate is 0.25 ℃/minute, and the cooling rate is 2 ℃/minute after sintering;
(5) Putting the ceramic obtained in the step (5) into a muffle furnace for air annealing at the annealing temperature of 1000 ℃, the heat preservation time of 50h, the heating rate of 0.25 ℃/min, and the cooling rate of 2 ℃/min after sintering; the relative density of the ceramic was 99.2%.
And (3) polishing the two sides of the sintered transparent ceramic until the thickness of the ceramic is 1.0mm to obtain the fluorescent ceramic with high thermal stability and high quantum efficiency, wherein the real object of the fluorescent ceramic is a blue-yellow transparent ceramic, and characters below the ceramic are clearly visible (as numbered 1 in figure 1).
(Lu) obtained in this example 0.596 Y 0.4 Ce 0.004 ) 3 (Al 0.4 Sc 0.6 ) 2 Al 3 O 12 XRD testing of the fluorescent ceramic is carried out, and the result is shown in figure 2, which shows that: the prepared material is a pure garnet phase.
(Lu) obtained in this example 0.596 Y 0.4 Ce 0.004 ) 3 (Al 0.4 Sc 0.6 ) 2 Al 3 O 12 The fluorescent ceramic is observed under a scanning electron microscope, and the result is shown in figure 3, and the ceramic crystal grain size is uniform and is not existedThe presence of the impurity phase is consistent with the XRD test result.
(Lu) obtained in the example 0.596 Y 0.4 Ce 0.004 ) 3 (Al 0.4 Sc 0.6 ) 2 Al 3 O 12 Under the excitation of the wavelength of 460nm, as shown in FIG. 4, the main peak of the emission spectrum of the fluorescent ceramic is 539nm, and the full width at half maximum is 102nm. The ceramic is excited by a 460nm blue LED chip (I =350 mA) to carry out an electroluminescence spectrum test, and as shown in FIG. 5, the ceramic can realize cyan-green light emission and has a color temperature of 10000K.
(Lu) obtained in this example 0.596 Y 0.4 Ce 0.004 ) 3 (Al 0.4 Sc 0.6 ) 2 Al 3 O 12 The fluorescent ceramic is subjected to an emission spectrum test with temperature change. The results are shown in FIG. 6, indicating that: the luminous intensity of the ceramic is gradually reduced along with the increase of the temperature, and the luminous intensity is only reduced by 2.3 percent at 150 ℃. The internal quantum efficiency was 88%.
(Lu) obtained in this example 0.596 Y 0.4 Ce 0.004 ) 3 (Al 0.4 Sc 0.6 ) 2 Al 3 O 12 The transmittance test of the fluorescent ceramic is carried out, and the result is shown in fig. 9, which shows that: the fluorescent ceramic has a transmittance T =69.06% @800nm.
Example 2: the preparation chemical formula is (Lu) 0.385 Y 0.6 Ce 0.015 ) 3 (Al 0.2 Sc 0.8 ) 2 Al 3 O 12 Fluorescent ceramic
(1) Setting the mass of the target product to be 60g according to the chemical formula (Lu) 0.385 Y 0.6 Ce 0.015 ) 3 (Al 0.2 Sc 0.8 ) 2 Al 3 O 12 Weighing alpha-alumina (14.36 g), yttrium oxide (16.84 g), lutetium oxide (19.04 g), scandium oxide (9.14 g) and cerium oxide (0.64 g) as raw material powder according to the stoichiometric ratio of the elements; mixing the raw material powder with 180ml of absolute ethyl alcohol, adding 270g of alumina balls with the diameter of 2mm, and performing ball milling in an alumina ball milling tank, wherein the ball milling speed is 190r/min, and the ball milling time is 25h;
(2) And (2) placing the mixed slurry subjected to ball milling in the step (1) into a 70 ℃ forced air drying oven for drying for 10 hours, and sieving the dried mixed powder with a 150-mesh sieve for 4 times.
(3) Putting the calcined powder in the step (2) into a grinding tool for dry pressing and molding, and then carrying out cold isostatic pressing molding, wherein the relative density of the molded biscuit is 52%;
(4) Sintering the ceramic biscuit obtained in the step (4) in a vacuum furnace, wherein the sintering temperature is 1750 ℃, the heat preservation time is 6 hours, the heating rate is 0.5 ℃/min, and the cooling rate is 4 ℃/min after sintering;
(5) Placing the ceramic obtained in the step (5) into a muffle furnace for air annealing at the annealing temperature of 1150 ℃, the heat preservation time of 20h, the heating rate of 0.5 ℃/min, and the cooling rate of 4 ℃/min after sintering; the relative density of the ceramic was 99.9%.
And (3) polishing the two sides of the sintered transparent ceramic to the thickness of 1.0mm to obtain the fluorescent ceramic with high thermal stability and high quantum efficiency, wherein the real object of the fluorescent ceramic is a blue-yellow transparent ceramic, and characters below the ceramic are clearly visible (as the number 2 in figure 1).
(Lu) obtained in this example 0.385 Y 0.6 Ce 0.015 ) 3 (Al 0.2 Sc 0.8 ) 2 Al 3 O 12 XRD test is carried out on the fluorescent ceramic, and the test result is shown in figure 2, which shows that: the prepared material is a pure garnet phase.
(Lu) obtained in this example 0.385 Y 0.6 Ce 0.015 ) 3 (Al 0.2 Sc 0.8 ) 2 Al 3 O 12 The emission spectrum of the fluorescent ceramic under 460nm wavelength excitation is shown in FIG. 7, and the main peak of the emission spectrum is 546nm and the full width at half maximum is 110nm. The ceramic is excited by a 460nm blue LED chip (I =350 mA) to carry out an electroluminescence spectrum test, and as shown in FIG. 8, green and yellow light emission can be realized, and the color temperature is 4000K.
(Lu) obtained in this example 0.385 Y 0.6 Ce 0.015 ) 3 (Al 0.2 Sc 0.8 ) 2 Al 3 O 12 The fluorescent ceramic is subjected to emission spectrum testing as a function of temperature. The results show that: the luminous intensity of the ceramic gradually decreases with increasing temperature, and the luminous intensity only decreases by 4.8% at 150 ℃. The internal quantum efficiency was 82%.
(Lu) obtained in this example 0.385 Y 0.6 Ce 0.015 ) 3 (Al 0.2 Sc 0.8 ) 2 Al 3 O 12 The transmittance test of the fluorescent ceramic is carried out, and the result is shown in fig. 9, which shows that: the fluorescent ceramic has a transmittance T =63.61% @800nm.
Comparative example: the preparation chemical formula is (Lu) 0.997 Ce 0.003 ) 3 (Al 0.5 Sc 0.5 ) 2 Al 3 O 12 Fluorescent ceramic
(1) The target product mass is set to be 60g according to the chemical formula (Lu) 0.997 Ce 0.003 ) 3 (Al 0.5 Sc 0.5 ) 2 Al 3 O 12 Respectively weighing alpha-alumina (14.07 g), lutetium oxide (41.07 g), scandium oxide (4.75 g) and cerium oxide (0.11 g) as raw material powder according to the stoichiometric ratio of the elements; mixing the raw material powder with 150ml of absolute ethyl alcohol, adding 240g of alumina balls with the diameter of 1.5mm, and carrying out ball milling in an alumina ball milling tank, wherein the ball milling speed is 185r/min, and the ball milling time is 20h;
(2) Putting the mixed slurry subjected to ball milling in the step (1) into a 60 ℃ forced air drying oven for drying for 10 hours, and sieving the dried mixed powder with a 50-mesh sieve for 6 times;
(3) Putting the calcined powder in the step (2) into a grinding tool for dry pressing and molding, and then carrying out cold isostatic pressing molding, wherein the relative density of the molded biscuit is 51.5%;
(4) Sintering the ceramic biscuit obtained in the step (4) in a vacuum furnace, wherein the sintering temperature is 1700 ℃, the heat preservation time is 6 hours, the heating rate is 0.25 ℃/min, and the cooling rate is 2 ℃/min after sintering;
(5) Placing the ceramic obtained in the step (5) into a muffle furnace for air annealing at 1050 ℃, wherein the heat preservation time is 15h, the temperature rise rate is 0.25 ℃/min, and the temperature drop rate is 2 ℃/min after sintering; the relative density of the ceramic was 99.1%.
And (3) polishing the two surfaces of the sintered transparent ceramic to the thickness of 1.0mm to obtain the fluorescent ceramic, wherein the actual object of the fluorescent ceramic is a blue-yellow transparent ceramic, and characters below the ceramic are covered (as shown in figure 10).
(Lu) obtained in this comparative example 0.997 Ce 0.003 ) 3 (Al 0.5 Sc 0.5 ) 2 Al 3 O 12 XRD test is carried out on the fluorescent ceramic, and the test result is shown in figure 2, which shows that: the prepared material is garnet phase and scandium oxide phase.
(Lu) obtained in this comparative example 0.997 Ce 0.003 ) 3 (Al 0.5 Sc 0.5 ) 2 Al 3 O 12 The fluorescent ceramic is observed under a scanning electron microscope, and the result is shown in fig. 11, and it can be seen that an obvious impurity phase exists, and the main phase crystal grains and the impurity phase of the ceramic coexist.
(Lu) obtained in the example 0.997 Ce 0.003 ) 3 (Al 0.5 Sc 0.5 ) 2 Al 3 O 12 When the fluorescent ceramic is excited by 460nm wavelength, the main peak of the emission spectrum is 519nm, and the full width at half maximum is 88.7nm. The ceramic is excited by an LED chip (I =350 mA) with blue light of 460nm to carry out electroluminescence spectrum test, and can realize deep blue light emission and color temperature of 8400K.
Obtained in this comparative example (Lu) 0.997 Ce 0.003 ) 3 (Al 0.5 Sc 0.5 ) 2 Al 3 O 12 The fluorescent ceramic is subjected to emission spectrum testing as a function of temperature. The results show that: the luminous intensity of the ceramic gradually decreases with increasing temperature, and the luminous intensity decreases by 21.4% at 150 ℃. The internal quantum efficiency was 72%.
(Lu) obtained in this comparative example 0.997 Ce 0.003 ) 3 (Al 0.5 Sc 0.5 ) 2 Al 3 O 12 The fluorescent ceramic was subjected to a transmittance test, as shown in fig. 9, and the results showed that: the fluorescent ceramic has a transmittance T =0.34% @800nm.
Claims (7)
1. A preparation method of high-thermal stability and high-quantum efficiency fluorescent ceramic for a white light LED/LD is characterized in that the chemical formula of the fluorescent ceramic is as follows:
(Y y Ce z Lu 1-z-y ) 3 (Sc x Al 1-x ) 2 Al 3 O 12
wherein,xis Sc 3+ Doped octahedral Al 3+ The mole percentage of the sites is,yis Y 3+ Doped Lu 3+ The mole percentage of the sites is,zis Ce 3+ Doped Lu 3+ Mole percent of sites, 0.5<x≤0.8，0.4≤y≤0.6，y：x=2：3~3：4，0<z is less than or equal to 0.015; when the environmental temperature is 150 ℃, the luminous intensity of the fluorescent ceramic is attenuated by 2-5%, and the internal quantum efficiency is 82-88%;
sintering by adopting a solid-phase reaction method, which comprises the following steps:
(1) According to the chemical formula (Y) y Ce z Lu 1-z-y ) 3 (Sc x Al 1-x ) 2 Al 3 O 12 ，0.5<x≤0.8，0.4≤y≤0.6，y：x=2：3~3：4，0<Respectively weighing alpha-alumina, yttrium oxide, lutetium oxide, scandium oxide and cerium oxide as raw material powder according to the stoichiometric ratio of each element with z being less than or equal to 0.015; mixing and ball-milling the raw material powder and a ball-milling medium to obtain mixed slurry;
(2) Placing the mixed slurry obtained in the step (1) in a drying oven for drying, and sieving the dried mixed powder;
(3) Placing the powder sieved in the step (2) into a grinding tool for forming, and then carrying out cold isostatic pressing forming to obtain a biscuit with the relative density of 51-52%;
(4) Sintering the biscuit obtained in the step (3) in a vacuum furnace at the sintering temperature of 1680-1750 ℃ for 6-10 h, wherein the sintering vacuum degree is not lower than 10 -4 Pa, obtaining fluorescent ceramic;
(5) And (5) carrying out air annealing treatment on the fluorescent ceramic subjected to vacuum sintering in the step (4), wherein the annealing temperature is 1000-1150 ℃, and the heat preservation time is 20h-50h, so as to obtain the fluorescent ceramic with the relative density of 99.2-99.9%.
2. The preparation method of the fluorescent ceramic with high thermal stability and high quantum efficiency for the white light LED/LD according to claim 1, wherein in the step (1), the ball milling rotation speed is 170r/min to 190r/min, and the ball milling time is 25h to 40h.
3. The method for preparing high thermal stability and high quantum efficiency fluorescent ceramic for white light LED/LD according to claim 1, wherein in the step (1), the ball milling medium is absolute ethyl alcohol, and the volume ratio of the mass of the raw material powder to the ball milling medium is 1g:2 to 3mL.
4. The preparation method of the high-thermal-stability high-quantum-efficiency fluorescent ceramic for the white LED/LD according to claim 1, wherein in the step (2), the drying time is 10h to 15h, and the drying temperature is 60 ℃ to 70 ℃.
5. The method for preparing high-thermal stability and high-quantum efficiency fluorescent ceramic for the white light LED/LD according to claim 1, wherein in the step (2), the mesh number of the sieved screen is 50-150 meshes, and the sieving frequency is 4-6 times.
6. The method for preparing a high thermal stability and high quantum efficiency fluorescent ceramic for a white LED/LD according to claim 1, wherein in the step (4), the temperature rise rate in the vacuum sintering stage is 0.25 to 0.5 ℃/min, and the temperature fall rate after sintering is 2 to 4 ℃/min.
7. The method for preparing a high thermal stability and high quantum efficiency fluorescent ceramic for a white LED/LD according to claim 1, wherein in the step (5), the temperature rise rate in the air annealing stage is 0.25 to 0.5 ℃/min, and the temperature fall rate after sintering is 2 to 4 ℃/min.
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