CN102732946A - Preparation method of F and Er ion double-doped green luminescent lead tungstate crystal - Google Patents

Abstract

The invention relates to a preparation method of highly translucent lead tungstate crystals with green luminescence property, belonging to the technical field of preparing luminescent crystals. The method is characterized by mainly using an improved crucible descent method and a technique of layer-by-layer doping to grow cation-anion double-doped lead tungstate crystals with high translucency in the development process. According to the invention, double doping of F<-> and Er<3+> ions is used, the F<-> and Er<3+> ions are doped in the forms of PbF2 powder and Er2O3 powder with the doping amount of 300-600 ppm and 100-300 ppm, and the volatilization of the F<-> is prevented by conducting layer-by-layer doping of the F<-> ions, and a platinum crucible is used for growing. The method can simultaneously grow multiple PWO crystals with green luminescence property, and can be used for batch production.

Description

The preparation method of the green luminous crystal of lead tungstate of F and the codope of Er ion

Technical field

The present invention relates to plumbous tungstate scintillation crystal preparation method, is to make crystal of lead tungstate the green characteristics of luminescence occur through specific doping way, belongs to the luminescent crystal preparing technical field.

Background technology

Crystal of lead tungstate is to belong to tetragonal system, synthetic be the Scheelite structure, it is to belong to PbO-WO ₃Brilliant the stopping of stable chemistry in the two component system.Crystal of lead tungstate is water white transparency in the visible region, double refraction, not deliquescence.Density is 8.28 g/cm ³, exponent of refractive index is n at the 600nm place _o/ n _e=2.242/2.169, optics elastic constant 0.13 MPa ^-1, internal stress constant 0.67 MPa, congruent melting compound, 1123 ℃ of fusing points.

The forties in 20th century, people have begun crystal of lead tungstate has been carried out some performance studies, but do not cause people's attention at that time.As scintillation crystal; Since plumbous tungstate have high-density, soon luminous, low-cost, anti-irradiation ability by force, lot of advantages such as can produce in batches; The nineties in 20th century; Nucleon center, Europe successfully is applied to the scintillation material in the LHC electromagnetic calorimeter, and so far, huge economic potential and development potentiality that people begin this material is contained have produced keen interest.The luminous mechanism of plumbous tungstate; The problem of aspects such as radiation damage mechanism and doping effect becomes the emphasis of scientists study; Some is also furtherd investigate the defect state that influences scintillation properties that exists in the PWO crystal; Hoping can be on this basis through optimizing growth conditions, and technologies such as doping or post-processed improve the crystalline scintillation properties, reach the strict demand that electromagnetic calorimeter of new generation proposes scintillation crystal.The low weakness of plumbous tungstate (PWO) crystal light output has seriously limited the application in its field beyond high energy physics in addition, breaks through the output of PWO crystal light to open up one of its focus that has also become the research of PWO crystal in the application aspect the PET detection equipment.Show [4] according to relevant expert's research: doubly reach 60-90p.e/MeV if make PWO crystalline light export fast component raising 2-3; To can be used for low side PET equipment. with capture PET at present and compare with the BGO crystal of the scintillator 50% above market share; Use the PWO crystal of high-density and short attenuation length can make the linear length of detector of PET system reduce half the approximately; Can make detector in a sizable effective field of view (FOV), keep better spatial resolution; Can bring into play simultaneously the fast luminous advantage of PWO again, improve the temporal resolution of PET equipment, PWO crystalline low cost also can make equipment cost also greatly reduce.And PET such as LSO, GSO to compare with PWO crystal high performance price ratio with scintillator also be unrivaled.Therefore, research PWO crystal not only has significance to nuclear medicine and high energy physics, but also has huge social benefit and economic benefit.

Because the PWO crystal has wide application space and great demand, crystal of lead tungstate is carried out doping vario-property research also become the direction that a lot of at present experts both at home and abroad are absorbed in.

Summary of the invention

The present invention relates to the PWO crystal preparation method of a kind of F and the green luminescent properties of Er ion codope.

The green luminous crystal of lead tungstate preparation method of a kind of F and the codope of Er ion is characterized in that having following process and step:

A, with purity 99.99% PbO and WO ₃Powder according to stoichiometric ratio weighing and burden (accuracy requirement reaches 0.0001g), adds prior load weighted doping agent Er simultaneously ₂O ₃Powder (weighing precision requires to be 0.0001g), thorough mixing is even, takes out and wherein 1/3rd mixes prior load weighted PbF ₂Powder, thorough mixing is even, and this part compound is put into crucible bottom, fills after solid placed on it with other 2/3rds again; Putting into seed crystal more effectively seals; The negatively charged ion that described doping agent is selected for use is F ^-, positively charged ion is Er ³⁺, its doping is respectively: PbF ₂Be 300ppm～900ppm, Er ₂O ₃Be 100ppm～600ppm;

B, used thickness are Φ 14 ~ 20mm or the square 14 * 14mm～20 * 20mm that the individual layer platinum paillon foil of 0.10 ~ 0.2mm is processed, and length is the crucible of 100 ~ 200mm, and crucible is through the sealing leak detection;

C, employing grain orientation are < 001 >, big or small Φ 10 ~ 20mm, and the single crystals of lead tungstate of long 50 ~ 70mm is as seed crystal;

D, the seed crystal of select and the material for preparing are packed in the crucible through the sealing leak detection, and carry out positiver sealing;

E, the platinum crucible of the good seal aluminum oxide of packing into is drawn down in the pipe, burnt Al is used in its gap ₂O ₃Powder is filled;

F, warp per hour 50 ~ 80 ℃ of speed rise to 1070 ~ 1100 ℃ with furnace temperature, are incubated then about 1 ~ 3 hour, and the aluminum oxide that rises gradually again draws pipe down; Raw material in the platinum crucible melts gradually, and insulation is about 1 ~ 2 hour after all melting into melt, and can carry out crystal growth this moment; Draw pipe down with 0.4 ~ 1.2mm/ hour speed decline then; Thermograde remains on 20 ~ 30 ℃/cm, owing to draw the decline of pipe down, the lower end temperature of crucible also constantly is reduced; So just make that melt constantly cools off, crystalline growth monocrystalline gradually above seed crystal;

After g, crystal growth are accomplished, furnace temperature is naturally cooled to room temperature, finally obtain crystal of lead tungstate.

The present invention adopts the doping pattern of zwitterion codope, when improving the output of crystal light, obtains having the crystal of lead tungstate of green luminescent properties.Because the powder of constitutive material all is to be sealed in platinum crucible and the present invention has adopted " layering doping " PbF ₂Method, so just effectively reduced PbO, WO ₃And PbF ₂Volatilization, can effectively improve the crystalline through performance.In addition; Adopt highly purified polycrystalline powder and stable crystal growing furnace; With two Si-Mo rods is pyrotoxin, growth zwitterion doped P WO crystal under certain growth conditions, and the temperature field of reactors is stable, the crystal radial symmetry gradient is little; Therefore the crystalline thermal stresses is little, has reduced the crystalline cracking.And can realize directed growing crystal in batches according to specified shape and size, a stove many crystal of can growing simultaneously.

Use the doping PWO crystal transmitance of the present invention's growth higher, and can produce tangible green luminescence phenomenon; Yield rate is high; Crystal property is consistent, favorable reproducibility; Technology is simple, and cost is low; Be fit to produce in batches.

Description of drawings

Fig. 1 is the multi-crucible lowering method synoptic diagram of growth PWO, and wherein (a) is many crucibles decline stove synoptic diagram; (b) be the synoptic diagram of growing during crystal is managed under aluminum oxide draws.

Fig. 2 is doping PWO crystal and purified PWO crystalline optical transmittance comparison diagram.

Fig. 3 is the doping PWO crystal and the PWO crystalline x-ray excited emmission spectrum figure that do not mix.

Embodiment

After specific embodiment of the present invention being described at present.

Embodiment 1

1, with purity is 99.99% high-purity PbO and WO ₃Powder is by accurately preparation also fully mixed evenly (being accurate to 0.0001g) of stoichiometric ratio.The corresponding 100ppm Er of weighing ₂O ₃Powder and 300ppmPbF ₂Powder.

2, seed crystal is selected: choose grain orientation and be < 001 >, overall dimensions is the PWO monocrystalline of 14 * 14 * 50mm;

3, highly purified platinum is purified, forged and suppress sheet through melting, being processed into thickness is 0.15mm, is of a size of the crucible of 15 * 15 * 150mm.

4, with adding load weighted doping agent Er in the mixed raw materials ₂O ₃Powder (weighing precision is 0.0001g), thorough mixing is even, takes out and wherein 1/3rd mixes load weighted PbF ₂Powder, thorough mixing is even once more, and this part compound is put into crucible bottom, fills after solid placed on itly with other 2/3rds again, puts into seed crystal again and effectively seals.

5, the platinum crucible of the good seal aluminum oxide of packing into is drawn down in the pipe, use the Al of calcination ₂O ₃Powder is filled its gap.And will draw to manage down and put into burner hearth.

6, through 50 ℃ of speed per hour furnace temperature is risen to 1080 ℃; Be incubated then about 2 hours, rise gradually and draw pipe down, the raw material in the platinum crucible is all fusings gradually at high temperature; Be incubated 2 hours once more; Can carry out crystal growth this moment, and the growth district thermograde is 30 ℃/cm, descends with 0.8mm/ hour speed and draw pipe down.

7, after growth is accomplished, furnace temperature is naturally cooled to room temperature, take out crystal;

Embodiment 2

1, with purity is 99.99% high-purity PbO and WO ₃Powder is by accurately preparation also fully mixed evenly (being accurate to 0.0001g) of stoichiometric ratio, the corresponding 600ppm Er of weighing ₂O ₃Powder and 900ppm PbF ₂Powder.

2, seed crystal is selected: choose grain orientation and be < 001 >, overall dimensions is the PWO monocrystalline of Φ 14 * 50mm;

3, highly purified platinum is purified, forged and suppress sheet through melting, being processed into thickness is 0.15mm, is of a size of the crucible of Φ 15 * 150mm.

4, adopt PbF ₂And Er ₂O ₃Two kinds of powders add the PbF of 300ppm respectively as doping agent in the powder for preparing ₂Er with 100 ppm ₂O ₃Powder, thorough mixing evenly install seed crystal then, the sealing platinum crucible;

5, process step is with the step 5. of embodiment 1

6, through 60 ℃ of speed per hour furnace temperature is risen to 1080 ℃; Be incubated then about 1 hour, rise gradually and draw pipe down, the raw material in the platinum crucible is all fusings gradually at high temperature; Be incubated 2 hours once more; Can carry out crystal growth this moment, and the growth district thermograde is 30 ℃/cm, descends with 0.8mm/ hour speed and draw pipe down.

7, this technology is with the step 7 of embodiment 1.

Embodiment 3

1, with purity is 99.99% high-purity PbO and WO ₃Powder is by accurately preparation also fully mixed evenly (being accurate to 0.0001g) of stoichiometric ratio, the corresponding 100ppm Er of weighing ₂O ₃Powder and 900ppm PbF ₂Powder.

2, process step is with the step 2 and 3 of embodiment 1.

3, highly purified platinum is purified, forged and suppress sheet through melting, being processed into thickness is 0.15mm, is of a size of the crucible of Φ 15 * 150mm.

4, process step is with the step 4 and 5 of embodiment 1.

5, through 70 ℃ of speed per hour furnace temperature is risen to 1080 ℃; Be incubated then about 1 hour, rise gradually and draw pipe down, the raw material in the platinum crucible is all fusings gradually at high temperature; Be incubated 2 hours once more; Can carry out crystal growth this moment, and the growth district thermograde is 30 ℃/cm, descends with 1.0mm/ hour speed and draw pipe down.

6, this technology is with the step 7 of embodiment 1

Embodiment 4

1, with purity is 99.99% high-purity PbO and WO ₃Powder is by accurately preparation also fully mixed evenly (being accurate to 0.0001g) of stoichiometric ratio, the corresponding 600ppm Er of weighing ₂O ₃Powder and 300ppm PbF ₂Powder.

2, process step with the step 2 of embodiment 1 to 5.

3, through 70 ℃ of speed per hour furnace temperature is risen to 1070 ℃; Be incubated then about 1 hour, rise gradually and draw pipe down, the raw material in the platinum crucible is all fusings gradually at high temperature; Be incubated 2 hours once more; Can carry out crystal growth this moment, and the growth district thermograde is 20 ℃/cm, descends with 1.0mm/ hour speed and draw pipe down.

4, this technology is with the step 7 of embodiment 1.

Embodiment 5

1, process step with the step 1 of embodiment 1 to 5.

2, through 70 ℃ of speed per hour furnace temperature is risen to 1090 ℃; Be incubated then about 1 hour, rise gradually and draw pipe down, the raw material in the platinum crucible is all fusings gradually at high temperature; Be incubated 2 hours once more; Can carry out crystal growth this moment, and the growth district thermograde is 20 ℃/cm, descends with 1.0mm/ hour speed and draw pipe down.

3, this technology is with the step 7 of embodiment 1.

Claims (1)

1. the green luminous crystal of lead tungstate preparation method of F and the codope of Er ion is characterized in that having following process and step:

A, with purity 99.99% PbO and WO ₃Powder is according to stoichiometric ratio weighing and burden (accuracy requirement reaches 0.0001g); Add prior load weighted doping agent Er simultaneously ₂O ₃Powder (weighing precision requires to be 0.0001g), thorough mixing is even, takes out and wherein 1/3rd mixes prior load weighted doping agent PbF ₂Powder, thorough mixing is even, and this part compound is put into crucible bottom, fills after solid placed on it with other 2/3rds again; Putting into seed crystal more effectively seals; The negatively charged ion that described doping agent is selected for use is F ^-, positively charged ion is Er ³⁺, its doping is respectively: PbF ₂Be 300ppm～900ppm, Er ₂O ₃Be 100ppm～600ppm;

B, used thickness are Φ 14 ~ 20mm or the square 14 * 14mm～20 * 20mm that the individual layer platinum paillon foil of 0.10 ~ 0.2mm is processed, and length is the crucible of 100 ~ 200mm, and crucible is through the sealing leak detection;

C. adopting grain orientation is < 001 >, big or small Φ 10 ~ 20mm, and the single crystals of lead tungstate of long 50 ~ 70mm is as seed crystal;

D, the seed crystal of select and the material for preparing are packed in the crucible through the sealing leak detection, and carry out positiver sealing;

E, the platinum crucible of the good seal aluminum oxide of packing into is drawn down in the pipe, burnt Al is used in its gap ₂O ₃Powder is filled;

F, warp per hour 50 ~ 80 ℃ of speed rise to 1070 ~ 1100 ℃ with furnace temperature, are incubated then about 1 ~ 3 hour, and the aluminum oxide that rises gradually again draws pipe down; Raw material in the platinum crucible melts gradually, and insulation is about 1 ~ 2 hour after all melting into melt, and can carry out crystal growth this moment; Draw pipe down with 0.4 ~ 1.2mm/ hour speed decline then; Thermograde remains on 20 ~ 30 ℃/cm, owing to draw the decline of pipe down, the lower end temperature of crucible also constantly is reduced; So just make that melt constantly cools off, crystalline growth monocrystalline gradually above seed crystal;

After g, crystal growth are accomplished, furnace temperature is naturally cooled to room temperature; Finally obtain crystal of lead tungstate.

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