CN1560890A - Cerium-doped lutetium-yttrium aluminate submicron imaging phosphor screen and preparation method thereof - Google Patents

Abstract

A cerium-doped lutetium-yttrium aluminate submicron imaging phosphor screen and a preparation method thereof, the structure of the phosphor screen is on a Lu _1-z Y _z AlO ₃ substrate whose crystal plane direction is (010), (100) or (001) It is formed by growing a layer of scintillation film Lu _1－x－y Ce _y Y _x AlO ₃ , where 0≤x≤0.9999, 0.0001≤y≤0.05, 0≤z≤1), the preparation method of the phosphor screen is to change the direction of the crystal plane Make a large-area seed crystal for (010), (100) or (001) Lu _1－z Y _z AlO ₃ (0≤z≤1) single crystal substrate, in the resistance heating liquid phase epitaxy furnace, in Lu _z At the crystallization temperature of Y _1-z AlO ₃ single crystal, a layer of micron and sub-micron Lu ₁ is grown on the contact interface with flux saturated solution containing Lu _1-x-y Ce _y Y _x AlO ₃ polycrystalline material _-x-y Ce _y Y _x AlO ₃ single crystal thin film. The phosphor screen is characterized by high efficiency and high resolution.

Description

Cerium-doped lutetium-yttrium aluminate submicron imaging phosphor screen and preparation method thereof

technical field

The invention relates to an X-ray submicron imaging fluorescent screen, in particular to a cerium-doped lutetium yttrium aluminate submicron imaging fluorescent screen and a preparation method thereof. in the detection field.

Background technique

X-ray radiography is a method of X-ray detection using scintillating fluorescent intensifying screens (scintillation crystals or phosphors) and photosensitive film. It is a traditional X-ray imaging technology. Wide range of applications. However, this traditional X-ray radiography has disadvantages such as low efficiency, time-consuming and labor-intensive, and incapable of real-time observation, etc., and has been gradually eliminated now. Using charge-coupled device (CCD) or amorphous silicon array (a-Si:H) detectors to replace photosensitive film in X-ray radiography, combined with computer-controlled display, is one of the important trends in the development of X-ray imaging technology in the future. Compared with traditional X-ray radiography, this new type of X-ray imaging technology has the advantages of high detection efficiency, high degree of digitalization, and online real-time detection. It has a very wide application value in the field. Moreover, with the development of the third-generation synchrotron radiation light source with high brightness and high resonance characteristics, this new type of X-ray imaging technology will also be used in the field of micro-X-ray imaging such as phase contrast imaging, holographic imaging, and micro-tomography. Microscopic X-ray imaging will require the system to have micron or submicron resolution, wider dynamic range, and faster time resolution. The scintillation phosphor screen is one of the key factors determining the spatial and temporal resolution of an X-ray imaging system. At present, most of the phosphor screens in the imaging system are 2-3 micron thick phosphor screens made of fine phosphor powder (with a particle size of 1 micron), and the resolution of such phosphor screens is generally on the order of 2-3 micron. In addition, due to the large particle size and density of the phosphor powder, which is only half the density of the corresponding crystalline film, the phosphor screen has disadvantages such as low X-ray absorption and light conversion efficiency, and long fluorescence response time. In order to improve the resolution of microscopic X-ray imaging, a single crystal scintillation film (SCF) with a thickness of only microns or submicrons has been developed as a fluorescent screen for X-ray imaging systems. This SCF fluorescent screen will greatly improve X-ray imaging. In theory, the resolution of the SCF scintillation fluorescent screen can reach the diffraction limit of visible light (about 0.3 microns). (See: IEEE Trans.Nucl.Sci.1998, Vol. 45, No. 5, p. 492; see: J.Opt.Sco.Am.A, 1998, Vol. 15, No. 7, p. 1940) .

There are mainly SCF fluorescent screens such as CsI(Tl), Ce:YAG/YAG and Ce:LuAG/YAG in the prior art, but these fluorescent screens have the following disadvantages: (1) CsI(Tl) and Ce: effective atomic number of YAG crystals and The densities are very small (Z _eff is 54.1 and 32, and the densities are 4.52 g/cm ³ and 4.55 g/cm ³ ), therefore, their X-ray absorption capacity and ray-to-light conversion efficiency are low. In order to improve its resolution, the thickness of the film must be increased. According to the imaging line spread function (LSF), the increase of the thickness will reduce the resolution of the fluorescent screen (the resolution is approximately equal to their thickness); (2) Although Ce:LuAG has a large Large effective atomic number and high density (Z _eff =58.9, density =6.67g/cm ³ ), but its light output is small (3000Ph/Mev), and the lattice between LuAG and YAG as the substrate This is not conducive to the growth of high-quality single crystal thin films on the substrate, which will seriously affect the optical properties of the fluorescent screen; (3) In addition, the CsI(Tl) thin film is easy to deliquescence, and its light decay time is longer ( 600ns), not suitable for fast real-time microscopic X-ray imaging; (4) In addition, the resolution of the SCF films in the prior art is relatively small, about 0.7-0.8 microns.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the disadvantages of low density, low light output, long decay time, and low resolution of the SCF fluorescent screen in the prior art, and provide a submicron imaging fluorescent screen doped with cerium-doped lutetium aluminate and its preparation method . The phosphor screen should be characterized by high efficiency and high resolution.

Technical solution of the present invention is as follows:

A cerium-doped lutetium-yttrium aluminate submicron imaging phosphor screen, the structure of the phosphor screen is Lu _1-z Y _z AlO ₃ (0≤z≤1) in the crystal plane direction of (010), (100) or (001) A layer of scintillation film Lu _1-xy Ce _y Y _x AlO ₃ is grown on the substrate, that is, Lu _1-xy Ce _y Y _x AlO ₃ /Lu _1-z Y _z AlO ₃ (0≤x≤0.9999, 0.0001≤ y≤0.05, 0≤z≤1).

The thickness of the Lu _1-z Y _z AlO ₃ (0≤z≤1) substrate is 5-30 microns, and the thickness of the scintillation film Lu _1-xy Ce _y Y _z AlO ₃ is 0.3-10 microns.

The preparation method of the cerium-doped lutetium-yttrium aluminate submicron imaging phosphor screen is characterized in that the phosphor screen is Lu _1-z Y _z AlO ₃ (0 ≤z≤1) single crystal substrate as a large-area seed crystal, in a resistance heating liquid phase epitaxy furnace, at the crystallization temperature of Lu _z Y _1-z AlO ₃ single crystal, and containing Lu _1-xy Ce _y Y _x A layer of micron and submicron Lu _1-xy Ce _y Y _x AlO ₃ single crystal film is grown on the contact interface of flux saturated solution of AlO ₃ polycrystalline material.

The raw material ratio of the polycrystalline flux saturated solution containing Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05) is as follows:

① The component distribution ratio of the flux solution is 8-15mol of PbO and 1mol of B ₂ O ₃ , or 10-12mol of Bi ₂ O ₃ and 1-3mol of B ₂ O ₃ ;

②The weight percent of Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05) polycrystal and flux is: Lu _1-xy Ce _y Y _x AlO ₃ /flux solution=10wt% -50wt%

The structure of the resistance heating liquid phase epitaxy furnace mainly includes:

Furnace body, the lower part of the furnace body is the main furnace body, and the upper part of the furnace body is the annealing furnace body. In the furnace body, there is a crucible in the center, which is coaxial with the furnace body. The periphery of the body is an insulating layer, and there is an insulating layer under the crucible and a bottom bracket that can adjust the height of the crucible. There is an upper side heating element in the annealing furnace, and the main furnace body is also equipped with a middle temperature measuring thermocouple. Coupled, a rotating lifting rod extends downward from the center of the upper top cover of the furnace body. The lower end of the rotating lifting rod is a substrate holder, and the rotating lifting rod is coaxial with the furnace body.

The preparation method of the cerium-doped lutetium-yttrium aluminate submicron imaging fluorescent screen comprises the following steps:

<1> Weigh the raw materials according to the selected ratio of Lu _1-xy Ce _y Y _x AlO ₃ polycrystal and flux, mix well and put them into the crucible of the resistance heating liquid phase epitaxy furnace and put them into the furnace body ;

<2> Put the Lu _1-z Y _z AlO ₃ (0≤z≤1) substrate wafer with crystal plane direction (100) or (010) or (001) into the substrate holder, and adjust the rotating puller , so that it is on the coaxial position of the crucible;

<3>Raise the temperature to 1050-1200°C at a heating rate of 100°C/Hr, melt polycrystalline raw material Lu _1-xy Ce _y Y _x AlO ₃ and flux PbO-B2O3 or Bi2O3-B2O3; make it a saturated solution (10 ), after being completely dissolved, keep the temperature at 1100-1250°C for 5 hours;

<4> Gradually lower and rotate the lifting rod to lower the substrate wafer to 3-5mm from the saturated flux liquid level, and then keep the crystallization temperature range of 900-1150℃ in Lu _1-xy Ce _y Y _x AlO ₃ for 2-4 Hour;

<5> Lower the rotating lifting rod so that the substrate wafer just touches the saturated solution. The rotating lifting rod rotates at a speed of 100-400r/min. According to the required growth Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05) Film thickness adjustment corresponding growth time, generally 3-20 minutes, after the growth time is over, lift the rotating lifting rod immediately to make the substrate out of the liquid surface;

<6> For annealing, continue to lift the rotating lifting rod, so that the substrate wafer and the Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05) film deposited on it enter the annealing process. For the upper heating element section in the furnace, adjust the power of the upper heating element to keep the temperature at 900°C for 30-60 minutes, then cool down to room temperature at a rate of 50°C/hr to complete Lu _1-xy Ce _y Y _x AlO ₃ /Lu _1-z Y _z AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05, 0≤z≤1) scintillation screen preparation.

Before step <5> lowering and rotating the lifting rod, first adjust the heating power of the side heating element of the main furnace body so that the temperature measuring thermocouple indicates 900-1150°C, keep the temperature for 1-2 hours, and then lower and rotate to lift Pull rod (6).

Technical effect of the present invention is as follows:

Compared with the prior art, the present invention, on the one hand, because the cerium ion-doped lutetium yttrium aluminate single crystal Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05) has a heavy density (density increases from 5.4 to 8.6g/cm ³ as x decreases), high effective atomic number, high light output (12000Ph/Mve and 15000Ph/Mve increases as x increases), fast decay (18- 30ns) etc., therefore, the fluorescent screen of the present invention has higher X-ray absorption coefficient and higher resolution than the fluorescent screen in the prior art; , there is no mismatch, the quality of the single crystal film is high, and the optical properties of the phosphor screen are good. In addition, the emission wavelength of this fluorescent screen is about 370nm, and its diffraction limit is smaller, which is more conducive to improving the resolution of the fluorescent screen (generally submicron).

Therefore, the scintillation fluorescent screen of the present invention can be widely used in various application fields of micro X-ray imaging.

Description of drawings

Fig. 1 is the resistance heating used for the preparation of Lu _1-xy Ce _y Y _x AlO ₃ /Lu _1-z Y _z AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05, 0≤z≤1) scintillation fluorescent screen of the present invention Schematic diagram of the cross-section of the liquid phase epitaxy furnace.

Detailed ways

Please refer to Figure 1 first, it can be seen from the figure that the present invention prepares Lu _1-xy Ce _y Y _x AlO ₃ /Lu _1-z Y _z AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05, 0≤z≤1 ) The structure of the resistance heating liquid phase epitaxy furnace used in the flashing fluorescent screen method mainly includes:

Furnace body 1, the lower part of the furnace body 1 is the main furnace body 101, and the upper part of the furnace body 1 is the annealing furnace body 102. In the furnace body 101, a crucible 9 is placed in the center, and the crucible 9 is coaxial with the furnace body 1. In the main furnace body 101, a side heating element 2 is arranged around the relative crucible 9, and the periphery of the side heating element 2 is an insulating layer 11. The crucible 9 There is a heat insulating layer 13 and a bottom support 12 that can adjust the height of the crucible 9. There is an upper side heating element 5 in the annealing furnace 102. The main furnace body 101 is also equipped with a middle temperature measuring thermocouple 3. The annealing furnace 102 is equipped with an upper temperature measuring thermocouple. Even, a rotating lifting rod 6 extends downward from the center of the upper top cover of the furnace body 1 , the lower end of the rotating lifting rod 6 is a substrate holder 7 , and the rotating lifting rod 6 is coaxial with the furnace body 1 .

The crucible 9 contains Lu _1-xy Ce _y Y _x AlO ₃ (0 ≤ x ≤ 0.9999, 0.0001 ≤ y ≤ 0.05) polycrystalline material and PbO-B ₂ O ₃ or Bi ₂ O ₃ -B ₂ O ₃ auxiliary solvent saturated solution. Extending down from the top of the furnace body is a rotating lifting rod 6, and at the lower end of the rotating lifting rod 6 there is a substrate holder 7, and a Lu _z Y _1-z AlO ₃ (0≤z≤1) lining is placed on the substrate holder 7. Bottom wafer stretches into crucible 9 li. The rotating lifting rod 6 is concentric with the furnace body 1 on the central axis. Around the crucible of the main furnace body 101, there is a side heating element 2, an insulating layer 11 is arranged on the periphery of the side heating element, an insulating layer 13 is arranged under the crucible 9 and a base 12 that can adjust the height of the crucible is arranged. Inside the annealing furnace 102 on the upper part of the furnace body 1 is an upper heating element 5 . The device also has a middle temperature measuring thermocouple 3, an upper temperature measuring thermocouple 4, and the like. The annealing furnace 102 in the furnace body 1 in the device of the present invention makes the thermal stress in the grown fluorescent screen to prevent cracking and the like.

The Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05) polycrystalline flux saturated solution used in the preparation method of the present invention is composed of Lu _1-xy Ce _y Y _x AlO ₃ Crystal material and flux lead oxide (PbO) and diboron trioxide (B ₂ O ₃ ) or bismuth oxide (Bi ₂ O3) and diboron trioxide (B ₂ O ₃ ) are prepared according to the following ratio:

The molar ratio of flux PbO to B ₂ O ₃ is PbO:B2O3=(8-15)mol:1mol; or take flux Bi ₂ O ₃ and B ₂ O ₃ , the ratio is Bi ₂ O ₃ : _{B 2} O ₃ = (10-12)mol: (1-3mol);

The weight percent of Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05) polycrystal and flux is: Lu _1-xy Ce _y Y _x AlO ₃ /flux=10wt%- 50wt%

The present invention will be further described in conjunction with following specific examples now.

Embodiment 1: Lu _0.9999 Ce _0.0001 AlO ₃ /luAlO ₃ fluorescent screen

The selected resistance heating liquid phase epitaxy furnace is as shown in FIG. 1 , and the crucible 9 in the main furnace 101 is a platinum crucible. According to the above-mentioned preparation process step <1>, the polycrystalline raw material Lu _0.9999 Ce _0.0001 AlO ₃ and the co-solvent (PbO: B2O3 = 10mol: 1mol) are prepared according to the weight percentage of Lu _0.9999 Ce _0.0001 AlO ₃ /(PbO+B2O3) = 0.20 Weigh a total of 1000g according to the proportion, mix it evenly, and put it into a platinum crucible 9 with a diameter of 80×80mm; according to the process step <2>, place 8 LuAlO ₃ substrates with a size of 30×0.03mm and a crystal plane direction of (010) in the fixture 7, and put the fixture 7 into the bottom end of the rotating lifting rod 6, adjust the position of the crucible 9 and the substrate wafer 8 to make it coaxial, and both are in the center of the main furnace body 101; Heat the furnace body 101 to 1150°C to melt the raw materials and flux to form a saturated solution 10, and after keeping the temperature at 1150°C for 5 hours, gradually lower and rotate the lifting rod 6 according to step <4>, so that the substrate wafer 8 is 4mm away from the saturated liquid surface , and then keep the temperature at 1050°C in the crystallization temperature range of Lu _0.9999 Ce _0.0001 AlO ₃ for 3 hours; lower and rotate the lifting rod 6 according to the above process step <5> to make the substrate wafer 8 just touch the saturated solution 10, and make the rotating lifting rod 6. Rotate at a speed of 300r/min. After growing at a constant temperature of 1050°C for 5 minutes, quickly lift off the rotating lifting rod 6 to remove the substrate wafer and the single crystal on it from the liquid surface, and the crystallization is completed; follow the above process steps <6 >Annealing is carried out, and the grown Lu _0.9999 Ce _0.0001 AlO ₃ single crystal is pulled together with the substrate wafer 8 to the heating element 5 section of the annealing furnace 102 above the furnace body 1. The temperature is lowered to room temperature at a rate of ℃/Hr, the annealing is completed, and the Lu _0.9999 Ce _0.0001 AlO ₃ /luAlO ₃ scintillation phosphor screen is prepared.

This kind of scintillation fluorescent screen has broad application prospects in microscopic X-ray imaging.

Example 2: Y _0.9999 Ce _0.0001 AlO ₃ /YAlO ₃ fluorescent screen

According to step <1> in the above example 1, Y _0.9999 Ce _0.0001 AlO ₃ polycrystalline material and cosolvent (Bi2O3: B2O3 = 8mol: 2mol) are Y _0.9999 Ce _0.0001 AlO ₃ /(Bi2O3+B2O3) = 0.40 by weight percentage Weigh a total of 1000g according to the proportion of the above-mentioned embodiment 1, according to the step <2> in the above-mentioned embodiment 1, the YAlO ₃ substrate 8 with a size of φ20×0.03mm and a crystal plane direction of (001) is placed in the fixture 7, and the fixture 7 Load the bottom end of the rotating lifting rod 6, adjust the position of the crucible 9 and the substrate wafer 8 to make it coaxial, and both are in the center of the main furnace body 101; according to <3> in the above embodiment 1, the furnace body 101 is heated to 1100°C, melt the raw material and the flux to form a saturated solution 10, and after keeping the temperature at 1100°C for 5 hours, gradually lower and rotate the lifting rod 6 according to <4> in the above-mentioned embodiment 1, so that the substrate wafer 8 is 3mm away from the saturated liquid surface, Then keep the temperature at 1000° C. in the crystallization temperature range of Y _0.9999 Ce _0.0001 AlO ₃ for 3 hours, lower and rotate the lifting rod 6 according to <5> in the above-mentioned embodiment 1 to make one end surface of the substrate wafer 8 contact with the liquid surface of the saturated solution 10, And make the rotating lifting rod 6 rotate at a speed of 200r/min, and after growing at a constant temperature at 1000°C for 10 minutes, quickly lift off the rotating lifting rod 6 to remove the substrate wafer and the single crystal on it from the liquid surface, and the crystallization is completed; press Step <6> of the above-mentioned Example 1 is annealed, that is, the grown Y _0.9999 Ce _0.0001 AlO ₃ single crystal is pulled together with the substrate wafer 8 into the heating zone of the annealing furnace 102 above the furnace body 1, and kept at a constant temperature of 900°C After 1 hour, the temperature was lowered to room temperature at a rate of 50° C./Hr, and the annealing was completed; the preparation of the Y _0.9999 Ce _0.0001 AlO ₃ /YAlO ₃ scintillation phosphor screen was completed.

Example 3: Y _0.995 Ce _0.005 AlO ₃ /YAlO ₃ fluorescent screen

According to step <1> in the above example 2, Y _0.9999 Ce _0.005 AlO ₃ polycrystalline material and co-solvent (Bi2O3: B2O3 = 10mol: 1mol) are Y _0.995 Ce _0.005 AlO ₃ /(Bi2O3+B2O3) = 0.40 by weight percentage Proportioning weighs a total of 1000g, and repeats steps <2>, <3>, <4>, <5>, <6> in the above-mentioned embodiment 2. Finally, the preparation of the Y _0.995 Ce _0.005 AlO ₃ /YAlO ₃ scintillation phosphor screen is completed.

Example 4: Lu _0.697 Y _0.3 Ce _0.003 AlO ₃ /Lu _0.7 Y _0.3 AlO ₃ fluorescent screen

According to step <1> in the above-mentioned embodiment 2, Lu _0.697 Y _0.3 Ce _0.003 AlO ₃ polycrystalline material and cosolvent (Bi2O3: B2O3 = 8mol: 2mol) were calculated as Lu _0.697 Y _0.3 Ce _0.003 AlO ₃ /(Bi2O3+ B2O3) = 0.50 proportioning to weigh a total of 1000g, according to the step <2> in the above-mentioned embodiment 2, the size is φ20 × 0.03mm, the crystal plane direction is (100) Lu _0.7 Y _0.3 AlO ₃ substrate 8 placed in the clamp 7, and the clamp 7 is loaded into the bottom end of the rotating lifting rod 6, and the position of the crucible 9 and the substrate wafer 8 is adjusted to make it coaxial, and they are all located in the center of the main furnace body 101; according to the above-mentioned embodiment 2 <3> Heat the furnace body 101 to 1150°C to melt the raw materials and flux to form a saturated solution 10, and after keeping the temperature at 1150°C for 5 hours, gradually lower and rotate the lifting rod 6 according to <4> in the above-mentioned embodiment 2, so that the substrate Wafer 8 is 3 mm away from the saturated liquid surface, and then kept at a temperature of 1050° C. in the crystallization temperature range of Lu _0.697 Y _0.3 Ce _0.003 AlO ₃ for 3 hours, and then lowered and rotated the lifting rod 6 according to <5> in the above-mentioned embodiment 2 to make the substrate wafer 8 The end surface is in contact with the liquid surface of the saturated solution 10, and the rotating lifting rod 6 is rotated at a speed of 400r/min. After growing at a constant temperature at 1050°C for 5 minutes, the rotating lifting rod 6 is quickly lifted away to make the substrate wafer and the single crystal on it From the liquid level, the crystallization is completed; annealing is carried out according to the step <6> of the above-mentioned embodiment 2, that is, the grown Lu _0.697 Y _0.3 Ce _0.003 AlO ₃ single crystal is pulled together with the substrate wafer 8 to the annealing furnace 102 above the furnace body 1 In the heat generating area, keep the temperature at 900°C for 50 minutes, then cool down to room temperature at a rate of 50°C/Hr, and the annealing is completed; the preparation of the Lu _0.697 Y _0.3 Ce _0.003 AlO ₃ /Lu _0.7 Y _0.3 AlO ₃ scintillating phosphor screen is completed.

The scintillation fluorescent screen has high resolution, and it can be widely used in medical, holographic imaging, phase contrast imaging and other application fields.

Claims (7)

1. A cerium-doped lutetium-yttrium aluminate submicron imaging fluorescent screen, characterized in that the structure of the fluorescent screen is (010), (100) or (001) Lu _1-z Y _z AlO ₃ (0 ≤z≤1) substrate and the scintillation film grown on it (Lu _1-xy Ce _y Y _x AlO ₃ , that is, Lu _1-xy Ce _y Y _x AlO ₃ /Lu _1-z Y _z AlO ₃ (0≤ x≤0.9999, 0.0001≤y≤0.05, 0≤z≤1). 2. The cerium-doped lutetium-yttrium aluminate submicron imaging fluorescent screen according to claim 1, characterized in that the Lu _1-z Y _z AlO ₃ (0≤z≤1) substrate has a thickness of 5-30 microns, The thickness of the scintillation film is 0.3-10 microns. 3. The method for preparing the cerium-doped lutetium-yttrium aluminate submicron imaging fluorescent screen according to claim 1, characterized in that the fluorescent screen is a Lu _1-z crystal plane whose orientation is (010), (100) or (001). Y _z AlO ₃ (0≤z≤1) single crystal substrate as a large-area seed crystal, in a resistance heating liquid phase epitaxy furnace, at the crystallization temperature of Lu _z Y _1-z AlO ₃ single crystal, with Lu ₁ A layer of Lu _{1- xy} Ce _y Y _x AlO ₃ single crystal thin film of micron and submicron scale is grown on the contact interface of flux saturated solution of -xy Ce _y Y _x AlO ₃ polycrystalline material. 4. The method for preparing the cerium-doped lutetium-yttrium aluminate submicron imaging phosphor screen according to claim 3, characterized in that the said phosphor screen contains Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y ≤0.05) The raw material ratio of polycrystalline flux saturated solution is as follows: ① The component distribution ratio of the flux solution is 8-15mol of PbO and 1mol of B ₂ O ₃ , or 10-12mol of Bi ₂ O ₃ and 1-3mol of B ₂ O ₃ ; ②The weight percent of Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05) polycrystal and flux is: Lu _1-xy Ce _y Y _x AlO ₃ /flux solution=10wt% -50wt% 5. The method for preparing cerium-doped lutetium-yttrium aluminate submicron imaging fluorescent screen according to claim 3, characterized in that the structure of the resistance heating liquid phase epitaxy furnace mainly includes: Body of furnace (1), body of furnace (1) bottom is main furnace body (101), body of furnace (1) top is annealing furnace body (102), and in body of furnace (101), crucible (9) is placed in the center, The crucible (9) is coaxial with the furnace body (1), and the main furnace body (101) is provided with a side heating element (2) around the relative crucible (9), and the periphery of the side heating element (2) is a heat insulating layer (11), There is an insulating layer (13) and a base (12) that can adjust the height of the crucible (9) under the crucible (9). There is an upper side heating element (5) in the annealing furnace (102), and the main furnace body (101) is also equipped with In the temperature measuring thermocouple (3), the annealing furnace (102) is provided with an upper temperature measuring thermocouple (4), and a rotating lifting rod (6) is extended downward from the center of the upper top cover of the furnace body (1). The lower end of the pull rod (6) is a substrate holder (7), and the rotating pull rod (6) is coaxial with the furnace body (1). 6. The method for preparing the cerium-doped lutetium-yttrium aluminate submicron imaging fluorescent screen according to claim 3, characterized in that the method comprises the following steps: <1> Weigh the raw materials according to the ratio of the selected Lu _1-xy Ce _y Y _x AlO ₃ polycrystal and flux, mix them well and put them into the crucible (9) of the resistance heating liquid phase epitaxy furnace and put them into In the furnace body (1); <2> Put the substrate wafer (8) of Lu _1-z Y _z AlO ₃ (0≤z≤1) whose crystal plane direction is (100) or (010) or (001) into the substrate holder (7) Inside, adjust the rotating lifting rod (6) so that it is on the coaxial position of the crucible (9); <3>Raise the temperature to 1050-1200°C at a heating rate of 100°C/Hr, melt polycrystalline raw material Lu _1-xy Ce _y Y _x AlO ₃ and flux PbO-B2O3 or Bi2O3-B2O3; make it a saturated solution (10 ), after being completely dissolved, keep the temperature at 1100-1250°C for 5 hours; <4> Gradually lower and rotate the lifting rod (6) to lower the substrate wafer (8) to 3-5mm from the saturated flux liquid level, and then crystallize in the Lu _1-xy Ce _y Y _x AlO ₃ temperature range of 900-1150°C Keep the temperature constant for 2-4 hours; <5> Lower the rotating lifting rod (6) so that the substrate wafer (8) just touches the saturated solution (10), and the rotating lifting rod (6) rotates at a speed of 100-400r/min to grow Lu _1-xy Ce as required _y Y _x AlO ₃ (0 ≤ x ≤ 0.9999, 0.0001 ≤ y ≤ 0.05) film thickness to adjust the corresponding growth time, generally 3-20 minutes, after the growth time is over, immediately lift the rotating lifting rod (6) to make the substrate (8) out of the liquid surface; <6> Annealing, will continue to lift the rotating lifting rod (6), so that the substrate wafer (8) and the Lu _1-xy Ce _y Y _x AlO ₃ (0≤x≤0.9999, 0.0001≤y) precipitated on it ≤0.05) the film enters the section of the upper heating element (5) in the annealing furnace (102), adjust the power of the upper heating element (5) to keep the temperature at 900°C for 30-60 minutes, and then at a speed of 50°C/hr Cool down to room temperature to complete the preparation of Lu _1-xy Ce _y Y _x AlO ₃ /Lu _1-z Y _z AlO ₃ (0≤x≤0.9999, 0.0001≤y≤0.05, 0≤z≤1) scintillation phosphor screen. 7. The method for preparing cerium-doped lutetium-yttrium aluminate submicron imaging fluorescent screen according to claim 6, characterized in that before step <5>, the main furnace body (101) is adjusted before the lifting rod (6) is lowered and rotated The heating power of the side heating element (2) makes the middle temperature measuring thermocouple (3) indicate 900-1150°C, keep the temperature constant for 1-2h, and then lower and rotate the lifting rod (6).