Technologies of luminescent material preparation: crystals growth

Transcription

1 1. Modern Materials Engineering. 2. Luminescent Materials in Medicine and Protection of Health Technologies of luminescent material preparation: crystals growth Yuriy Zorenko *Electronic Department, Ivan Franko National University of Lviv, Ukraine ** Institute of Physics, Jan Dlugosz University in Czestochowa, Poland

2 Types of luminescent materials Alkali-halides NaI:Tl CsI:Tl CsI:Na BaFBr:Eu CsBr:Eu dopants Fluoride BaF Self-activated phosphors Defects Oxides CaWO 4 CdWO 4 PbWO 4 Bi 4 Ge 3 O 12 YAlO 3 :Ce LuAP:Ce Lu 2 SiO 5 :Ce Gd 2 SiO 5 :Ce Al 2 O 3 :C

3 Technology of material preparation Type of materials 1. Bulk crystals 2. Films scintillators - powder films; - single crystalline films; - columnar-grown film; 3. Transparent ceramic 4. Transparent nanoceramic Methods of preparations 1. XXXXXXX technique (large crystals) 2. ZZZZZZZ technique (large crystals) 3. MPD technique (small crystal) 4. Solid state reaction (ceramic) 5. Sol-gel technique (nanoceramic) 6. Film technique - Deposition from solution - Print technique; - Thermal vapor deposition; - Liquid phase epitaxy;

4 Q.1 Kto jest Polski uczony najczęściej wymieniany w literaturze światowej?

5 Kto jest Polski uczony najczęściej wymieniany w literaturze światowej? Urodzony w 1885 roku jako ósmy syn ubogiego stolarza. Nie jest pewne czy zdał maturę Nie stać go było na opłacenie studiów

6 Kto jest Polski uczony najczęściej wymieniany w literaturze światowej? Urodzony w 1885 roku jako ósmy syn ubogiego stolarza. Nie jest pewne czy zdał maturę Nie stać go było na opłacenie studiów Uznawany za "praojca elektroniki"

7 Kto jest Polski uczony najczęściej wymieniany w literaturze światowej? Urodzony w 1885 roku jako ósmy syn ubogiego stolarza. Nie jest pewne czy zdał maturę Nie stać go było na opłacenie studiów Uznawany za "praojca elektroniki" Odkrywca metody wzrostu kryształów

8 Kto jest Polski uczony najczęściej wymieniany w literaturze światowej? Urodzony w 1885 roku jako ósmy syn ubogiego stolarza. Nie jest pewne czy zdał maturę Nie stać go było na opłacenie studiów Uznawany za "praojca elektroniki" Odkrywca metody wzrostu kryształów Prof Jan Czochralski October 23, 1885 in Kcynia - April 22, 1953 in Poznań

9 Technology of material preparation Type of materials 1. Bulk crystals 2. Films scintillators - powder films; - single crystalline films; - columnar-grown film; 3. Transparent ceramic 4. Transparent nanoceramic Methods of preparations 1. Czochralski technique (large crystals) 2. Bridgman technique (large crystals) 3. MPD technique (small crystal) 4. Solid state reaction (ceramic) 5. Sol-gel technique (nanoceramic) 6. Film technique - Deposition from solution - Print technique; - Thermal vapor deposition; - Liquid phase epitaxy;

10 Czochralski technique Scheme of equipment for growth of crystal by Czochralski methods : 1 crucible with melt, 2 - crystal, 3 furnace, 4,5 translation and rotation mechanism Main characteristics of methods: 1. High temperature o C melt with large interface water 2. Crucibles using Pt - low ~ o C temperatures Ir higher temperatures, but need the inert atmosphere or vacuum for oxygen protection Stage of crystal growth

11 Czochralski technique The first reported oxide material grown using the Czochralski technique was CaWO 4 in 1960 [5]. PbWO 4 crystal growth (2006)

12 Important parameters for crystal growth 1. Composition of melt 2. Growth atmosphere 3. Growth rate 4. Shape of front of crystallization 5. Crystal diameter control 6. Dimensions 7. Segregation coefficient of dopants 8. Quantity of intrinsic macro-defects and micro- defects 9. Price

13 Non-stoichiomtric composition of melt It was always assumed that the composition of oxide materials is stoichiometric; hence, the initial starting melt composition was also stoichiometric. mp This is wrong conclusion for complex oxides! The phase diagram (Fig. 1) shows the shift in the composition in the Li 2 O Nb 2 O 5 phase diagram from stoichiometric to congruent.

14 The congruently melting composition was 48.6% Li 2 O and crystals grown from this melt composition showed much lower variations in the structural and optical properties. Stoichiometric melt Congruent melt (a) (b) Polished crystal sections showing the change in the growth striations for a crystal grown from a stoichiometric melt (a) and grown from a congruent melt (b).

15 Growth of {RE} 3 [Ga 2x RE x ](Ga) 3 O 12 garnet crystal Part of phase diagram Gd 2 O 3 -Ga 2 O 3 oxides. In Gd 2 O 3 -Ga 2 O 3 at Т п =1720 о С the garnet Gd 3.05 Ga 4.95 O 12 is melted congruently. Y,Re Ga,Al Ga,Al Garnet compound T ( C) Ga2O (Y,Re)Al Creation of antisite defects in single crystals of garnets Fragment of garnet structure with Lu Al antisite defect

16 Growth of {RE} 3 [Ga(Al) 2x RE x ](Ga) 3 O 12 garnet crystals Segregation coefficient of dopants K= C (in melt) / C (in crystal) Lu With decreasing the ionic radius of RE ions the concentration of antisite defects is increase

17 Growth of Gd 3 Sc 2 Ga 3 O 12 (GSGG) garnet as laser material The congruent composition of GSGG was {Gd Sc }[Sc Ga ](Ga) 3 O12.

18 Local conclusion Unlike what was believedin the 1960s and 1970s, a nonstoichiometric, congruently melting composition appears as the rule rather than the exception and very few oxide materials exist as line compounds. Thus today, our current understanding of composition is: For most oxides, the congruently melting composition most probably is not the stoichiometric composition. The more complex the crystal structure, the higher the probability for nonstoichiometry to exist at the melting point. Materials with a crystal structure that have similar cation coordination sites are most likely to show nonstoichiometry at its melting point. Only simple oxides such as Al 2 O 3 tend to have congruent melting composition that is stoichiometric.

19 Shape of growth interface and its influence on the quality of the crystal Shape of the growth interface couldbe controlledby the crystal rotation rate Growth rate is ~ mm/h Rotation rate is ~5-40 rpm Conical interface was necessary to maintain stable growth Flat or convex interface shape result in unstable growth Conical flat convex Surface and bulk flow observed in water / glycerin simulations (a) slow rotation (b) moderate rotation (c) fast rotation.

20 Shape of interface between the crystal and melt

21 Crystal diameter control (in past) Problems: non-uniformity diameter of cylindrical part of crystal Initial control systems were based on control of the power input If the power input in the furnace is constant the diameter of crystal would be also constant. For the early low melting oxides such as CaWO 4, a thermocouple was placed in the liquid and provid the signal for diameter control

22 Crystal diameter control based on crystal waiting (today) The uniformity diameter of cylindrical part of crystal

23 Milestone of Czochralski technique in the oxide crystal growth

24 Methods of crystal growth: Czochralski technology Seed crystal chamber carbon heater carbon Ir, Pt crucible Yoshikawa Lab, IMRAM, Tohoku university, Sendai, Japan computer control rotary pump diffusion pump Czochralski grown PbWO 4 IP Prague, CR 8-inch-size BaF 2 T g = o C Czochralski grown YAlO 3 :Ce, Lu 3 Al 5 O 12 :Ce, CRYTUR LtD, Turnov, CzR

25 Crystal grows and mechanics-polishing equipment in Institute of Materials NAS, Kharkiv, Ukraine

26 Institute of materials (IM), Kharkv, Ukraine Apl. CT LHC CT PET PET PET

27 The Bridgman-Stockbarger method Percy Williams Bridgman Nobel prize 1946 Stage of growth 1. Sealing the starting materials in an ampoule 2. Melting 3. Crystal growth by passing the ampoule through the temperature gradient zone Halides NaI:Tl, CsI:Tl, CsI:Na, CsBr:Eu, etc.

28 Methods of crystal growth: Bridgman technique CsI:Tl crystals grown by the Bridgman methods

29 Methods of crystal growth: Bridgman technique W-Mo crucible Lu 3 Al 5 O 12 :Pr 3+ (a) and (Lu 1-x Gd x ) 3 Al 5 O 12 :Ce 3+ (b) crystals grown by Bridgman methods

30 Crystal Growth by Micro-Pulling-Down Technique

31 Yoshikawa Lab, IMRAM, Tohoku university, Sendai, Japan Methods of crystal growth: micro-pulling-down (MPD) technology melt Quartz tube Work coil Ar Ir crucible After heater Grown crystal Alumina stage Seed crystal <RF heating μ-pd furnace> Undoped YAP Pr 0.1 mol% Pr 0.5 mol% Grown crystals φ1mm φ3mm BaF 2 crystal

32 Conclusions 1. Over the past 40-th years we have large progress with the growth crystal from of small (1 cm diameter and 3 cm length, 100 g) crystals suitable for research to the growth of large oxide crystals that now are 75 mm or larger in diameter that can weigh as much as 30 kg. 2. We have a much better understanding of the impact of stoichiometry, growth atmosphere and furnace design on the quality of the resulting crystal. 3. As the optical and electronic industries demand for new materials highest performance, smaller component size and lower cost. 4. These new materials are being engineered for improved properties to for set of applications by using such techniques as coupled substitution, selective ion replacement or solid solutions.