CN101230484A - Growing method for carbon-doped sapphire crystal - Google Patents

Abstract

The invention relates to a method of growing a carbon-mixed sapphire crystal, is characterized in that the method of targeted gradient temperature is adopted to grow the Alpha-Al2O3: C crystal. The process flow is as follows: firstly, a certain qualitative amount of Alpha-Al2O3 is weighed and then graphite of 100 to 5,000 ppm is added in and stirred to mix well; secondly, oriented sapphire seed crystals are placed in the seed crystal tank of the molybdenum crucible in the temperature gradient furnace and the well-mixed powder lot is put into the crucible evenly and then the crucible is covered; and thirdly, the crucible is placed in the furnace. The furnace is vacuumized to be 5 by 10<-3>Pa, persistently overheated to be 2,080 DEG Cand kept constant for 0.5 to 1 hour and then the temperature is reduced to the room temperature at a velocity of 3 to 5 DEG C per hour and then the furnace mantle is unclosed to take out the crystal. The Alpha-Al2O3: C crystal directly grown in the invention has excellent thermoluminescence capability and high crystal quality, which can be used for manufacturing highly-sensitive thermoluminescent detectors.

Description

The growth method of carbon-doped sapphire crystal

Technical field

The present invention relates to carbon-doped sapphire crystal and (be designated hereinafter simply as α-Al ₂O ₃: the growth method of C) crystal, particularly a kind of carbon-doped sapphire crystal.Adopt the warm terraced method of guiding (Directional TemperatureGradient Technique, DTGT) α-Al of growth large-size ₂O ₃: C crystal, α-Al ₂O ₃: it is to be used to make thermoluminescent detector (TLD) that the C crystalline mainly acts on.

Background technology

M.S.Akselrod is early than finding α-Al the nineties in 20th century ₂O ₃: the C crystal has very excellent thermoluminescence performance, and the glow peak temperature is at 187 ℃, and the halfwidth at peak is 60 ℃, and thermoluminescence sensitivity is LiF:Mg, 40～60 times of Ti, and the background threshold dose only is 10 ^-6Gy (gray(Gy) is designated hereinafter simply as Gy), its dose response is linear sublinear, linearity range is 10 ^-6～10Gy.α-Al ₂O ₃: after the raying of C crystal, being subjected to thermoluminescent peak wavelength is 420nm, mainly is be heated excitation electron and F ⁺The compound generation of colour center.α-Al ₂O ₃: C crystalline thermoluminescence performance mainly is because the F colour center that exists in the crystal causes that causing of C causes oxygen ion vacancy defective Vo ^.., Vo ^..Capture two electronics and generate the F colour center (referring to M.S.Akselrod et.al.Highly sensitive thermoluminescent anion-defective α-Al ₂O ₃: C single crystal detectors, Radiation Protection Dosimetry, 1990,32:15-20).α-Al ₂O ₃: the C crystal is used to make thermoluminescent detector (TLD) and mainly contains following characteristics (M.S.Akselrod et. al.Preparation and Properties of α-Al ₂O ₃: C, RadiationProtection Dosimetry, 1993,47:159-164):

(1) thermoluminescence is highly sensitive, is the thermoluminescence crystal LiF:Mg that uses always, 40～60 times of Ti;

Near (2) 187 ℃ glow peak type is single, effective atomic number relatively low (10.2).

(3) low predose response threshold value, the background threshold dose only is 10 ^-6Gy;

(4) the radiation dose response is linearity-sublinear, and linear response range is wide, 10 ^-6～10Gy;

(5) α-Al ₂O ₃: the emission peak at C crystal 4 20nm place is in the best peak value of photomultiplier response;

(6) under the low dosage condition, α-Al ₂O ₃: the C crystal detector can be reused and need not anneal;

The warm terraced method that leads (Directional Temperature Gradient Technique, abbreviate DTGT as) be a kind of of temperature gradient method, this growing method is that early eighties waits the suitable growing large-size optics of invention, the growth method of laser crystals by professor Deng Peizhen of Shanghai ray machine institute, and initial growth goes out φ 54 * 45mm ³Al ₂O ₃Crystal (the warm terraced method that leads is given birth to the high-quality sapphire single-crystal for Cui Fengzhu, Zhou Yongzong etc., silicate journal, and 1980,8:109), crystal mass obviously is better than the crystal of Czochralski grown.In the past twenty years, the DTGT method is greatly improved and is perfect, the high-quality YAG that successively successfully grown, Nd:YAG, Ti:Al ₂O ₃, LiAlO ₂In crystal.The main difference of guiding temperature gradient method and crystal pulling method is: in the crystal growth of guiding temperature gradient method, solid-liquid interface is immersed in high-temperature fusant inside fully, and seed crystal is positioned at the groove of the bottom of molybdenum crucible; The thermograde direction of melt is opposite with the gravity field direction, and crystal, melt and crucible all keep stationary state.

Nineteen ninety, M.S.Akselrod anneals φ 5 * 500mm sapphire crystal under the condition that has graphite to exist under strongly reducing atmosphere, obtain α-Al ₂O ₃: the C crystal.The prerequisite of this method is the bar-shaped sapphire crystal of growth high-quality, and then reduced anneal, the technology relative complex, and be difficult to guarantee the uniform distribution of C in sapphire crystal, promptly be difficult to obtain the α-Al of quality homogeneous ₂O ₃: the C crystal.

Summary of the invention

The technical problem to be solved in the present invention is to overcome above-mentioned the deficiencies in the prior art, provides a kind of growth method of carbon-doped sapphire crystal, i.e. α-Al ₂O ₃: C crystalline growth method, to simplify α-Al ₂O ₃: C crystalline growth technique, improve α-Al ₂O ₃: C crystalline quality obtains α-Al that large size has good thermoluminescence performance ₂O ₃: the C crystal,

Technical solution of the present invention is as follows:

A kind of growth method of carbon-doped sapphire crystal, i.e. α-Al ₂O ₃: C crystalline growth method is characterized in adopting the warm terraced method growth α-Al of guiding ₂O ₃: the C crystal, technical process is as follows:

1. take by weighing the α-Al of certain mass ₂O ₃, add the graphite of 100～5000ppm therein, fully mix;

2. put into directed sapphire seed crystal at gradient furnace molybdenum crucible seed slot place, the powder that mixes is evenly put into crucible, cover crucible cover;

3. shove charge is evacuated to 5 * 10 ^-3Pa, persistently overheating to 2080 ℃, constant temperature 0.5～1 hour cools to room temperature with 3～5 ℃/hour speed then, opens bonnet, takes out crystal.

Restore annealing preparation α-Al with the long sapphire crystal of elder generation of M.S.Akselrod ₂O ₃: the C crystal is compared, and the present invention is with α-Al ₂O ₃With graphite be raw material, the α Al of large size (2 inches of Φ) that adopted the warm terraced method direct growth of guiding ₂O ₃: the C crystal, simplified growth technique, improved production efficiency.

The experiment proved that, adopt the α-Al of the inventive method direct growth ₂O ₃: the C crystal has good thermoluminescence performance, and crystal mass is good, can be used to make highly sensitive thermoluminescent detector (TLD).

Description of drawings

Fig. 1 is the used gradient furnace internal structure sectional view of the inventive method

Fig. 2 is the α-Al of the inventive method growth ₂O ₃: C crystalline absorption spectrum

Fig. 3 is α-Al ₂O ₃: the C crystal is through the thermoluminescence curve of x-ray irradiation after 10 seconds

Embodiment

The invention will be further described below in conjunction with embodiment, but should not limit protection scope of the present invention with this.

See also Fig. 1 earlier, Fig. 1 is the used gradient furnace internal structure sectional view of the inventive method.This gradient furnace is the bell-jar vacuum resistance furnace, the internal structure of this body of heater comprises crucible, heating element, crucible 1 place on the interior central position of body of heater, are cylinder graphite heaters 2 around it, be to go up heat protection screen 8 and side heat protection screen 9 around the heating element 2, be pot holder 3 below the crucible 1, the battery lead plate 6 that links to each other with heating element 2 is supported by support ring 7, and following heat protection screen 10 is arranged in the support ring 7, the center of battery lead plate 6 extends in the pot holder 3 water coolant pole 5, measures the thermopair 4 of temperature.

Attached vacuum system outside the body of heater, the graceful A2S1047 type of 60KW Mermithidae UPS voltage stabilized source and 818P4 Ou Lu precise temperature control system.Not shown in the figures.

Embodiment 1: mix the C amount and be α-Al of 5000ppm ₂O ₃: the growth of C crystalline

Take by weighing 500 gram α-Al respectively ₂O ₃With 2.50 gram graphite be 5000ppm, in mixer, mixed 24 hours, install standby with freshness protection package.In φ 50 * 80mm molybdenum crucible afterbody seed slot, put into the oriented seed of R (0112) direction, the powder for preparing is evenly put into crucible, cover crucible cover.Put the side heat protection screen well, make crucible be positioned at cylinder center, cover the top heat protection screen then successively, cover bell jar at last.Open mechanical pump, be evacuated to 5 * 10 ^-3Pa, opening power is persistently overheating to 2353K, and constant temperature 1 hour cools to room temperature with 5 ℃/hour speed then, opens bonnet, takes out crystal.

Through check, the α-Al of present embodiment ₂O ₃: the C crystal perfection, do not have gentle the bubbling out of obvious wrap and show.Along R (0112) direction is cut 5 * 5 * 1mm in crystal sheet, its absorption spectrum and thermoluminescence performance have been done detection.Fig. 2 is the α-Al of present embodiment growth ₂O ₃: C crystalline absorption spectrum, as can be seen from the figure, the uptake factor that this crystal is positioned at the 206nm place obviously strengthens, i.e. and the F colour center showed increased in the crystal is because causing of C causes anion vacancy defective Vo ^.., Vo ^..Capture two electronics and generate the F colour center.Fig. 3 is the α-Al of present embodiment growth ₂O ₃: the C crystal is through the thermoluminescence curve of x-ray irradiation after 10 seconds, 25 ℃/hour of temperature rise rates.As can be seen from the figure, the α-Al of the inventive method growth ₂O ₃: C crystalline glow peak is positioned at 187 ℃ to be located, halfwidth～65 ℃, and the thermoluminescence luminous intensity reaches 6 * 10 in the time of 187 ℃ ³Number of photons/second (Counts per second abbreviates cps as).In a word, the α-Al of warm terraced method growth ₂O ₃: the α-Al of C crystalline thermoluminescence performance and M.S.Akselrod report ₂O ₃: the C crystal property is suitable, but growth technique is simplified relatively.

Embodiment 2: mix the C amount and be α-Al of 100ppm ₂O ₃: the growth of C crystalline

Removing the graphite C of adding is 100ppm, cools to the room temperature growing crystal with 3 ℃/hour speed, and other batchings and growth step are with embodiment 1.α-Al that growth obtains ₂O ₃: the C crystal, crystalline structure is complete, does not have gentle the bubbling out of obvious wrap and shows, and crystal is positioned at the F colour center intensity and 187 ℃ of relative reductions of thermoluminescence intensity of locating at 206nm place, but the position of 187 ℃ of thermal glow peaks does not change.

Embodiment 3: mix the C amount and be α-Al of 2500ppm ₂O ₃: the growth of C crystalline

Removing the graphite C of adding is 2500ppm, cools to the room temperature growing crystal with 4 ℃/hour speed, and other batchings and growth step are with embodiment 1.α-Al that growth obtains ₂O ₃: the C crystal, crystalline structure is complete, does not have gentle the bubbling out of obvious wrap and shows, and has α-Al ₂O ₃: the C crystal is positioned at 187 ℃ feature thermal glow peak, and the F colour center intensity at 206nm place is bigger.

Claims (2)

1. α-Al ₂O ₃: C crystalline growth method is characterized in that it being to adopt the warm terraced method growth α-Al of guiding ₂O ₃: the C crystal, technical process is as follows:

1. take by weighing the α-Al of certain mass ₂O ₃, add the graphite of 100～5000ppm therein, fully mix;

2. put into directed sapphire seed crystal at gradient furnace molybdenum crucible seed slot place, the powder that mixes is evenly put into crucible, cover crucible cover;

3. shove charge is evacuated to 5 * 10 ^-3Pa, persistently overheating to 2080 ℃, constant temperature 0.5～1 hour cools to room temperature with 3～5 ℃/hour speed then, opens bonnet, takes out crystal.

2. according to the described α-Al of claim 1 ₂O ₃: C crystalline growing method is characterized in that α-Al ₂O ₃: the C crystal is used for thermoluminescent detector (TLD).

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