assoc. prof. dr. ayşen yilmaz department of chemistry middle east technical university ankara,...
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Assoc. Prof. Dr. Ayşen YILMAZDepartment of Chemistry
Middle East Technical UniversityAnkara, TURKEY
Prof. Dr. Gülhan ÖZBAYOĞLUDean Faculty of Engineering
Atılım University Ankara, Turkey
RAD, 24-27 April 2012
OBJECTIVES
To synthesize metal doped Li2B4O7 to be used in TL dosimetry by using different synthesis methods.
• high temperature solid state synthesis • solution assisted synthesis• doping with Cu and Mn• Co-doping with Ag and In together with Cu, of Ag, P and Mg together with Mn
To determine the thermoluminescence response.
THERMOLUMINESCENCE
HEATINGHEATING
LIGHT EMISSION
RADİATİON EXPOSURE
AND RESULTANT RADİATİON STORAGE
LITHIUM TETRABORATE
SYNTHESIS
Powder:
by heating hydrated precursors
by wet reaction
by solid state reactions
Pellet: ease in lab work, final product is fragile
Glass: cautious control of temperature (up to 1150oC) rapid cooling
employed
Crystal: require complicated systems, seed crystal
LITHIUM TETRABORATE
TL RESPONSE
▫Glow Curve: Generally around 200 O C
MATERIALS AND METHODS
2- METHODS
•Li2CO3 + 4H3BO3 Li2B4O7 + CO2 +6 H2O
DopingSynthesis Method
Material
Li2B4O7
High Temp.
Solid State
High Temp.
Solid State
Solution Assisted
Water /Solution
AssistedSolution Assisted
MATERIALS AND METHODSMATERIALS AND METHODS
MixingMixing
• Stoichiometric quantities of Li2CO3 and H3BO3
• Stoichiometric quantities of Li2CO3 and H3BO3
Initial HeatingInitial
Heating
• 0-400 oC by 400 oC per hr• Retention Time: 3 hr• Mixing,Pounding, Blending
• 0-400 oC by 400 oC per hr• Retention Time: 3 hr• Mixing,Pounding, Blending
Secondary
Heating
Secondary
Heating
• 400-750 oC by 400 oC per hr• 2 hr exposure• Intermittent mixing• 2 more hours
• 400-750 oC by 400 oC per hr• 2 hr exposure• Intermittent mixing• 2 more hours
High Temperature Solid State Synthesis
MATERIALS AND METHODS
Water / Solution Assisted Synthesis
StirringStirring• Li2CO3 and H3BO3 in 15 ml water• At 100-150 oC for 15-20 min
• Li2CO3 and H3BO3 in 15 ml water• At 100-150 oC for 15-20 min
Initial HeatingInitial
Heating
• 0-150 oC by 400 oC per hr• Retention Time: 3 hr• Mixing
• 0-150 oC by 400 oC per hr• Retention Time: 3 hr• Mixing
Secondary
Heating
Secondary
Heating
• 400-750 oC by 400 oC per hr• 4 hr exposure• 400-750 oC by 400 oC per hr• 4 hr exposure
MATERIALS AND METHODS
High Temperature Solid State Doping
Applied to high temp. solid state synthesis product only
0.1-1.0% Cu, 0.1-10% Mn doped
Heating 25-750oC by 400oC per hr
Retention2+1 hr with intermittent mixing
MATERIALS AND METHODS
Solution Assisted DopingFor water/solution assisted synthesis product
0.1-1% Cu
For high temp solid state synthesis product 0.1% Cu and 1.0 % Mn best results
Heating 150oC - 3 hrs, 700oC - 2 hrs
MATERIALS AND METHODS
LBO Weight (g) Cu % Ag % Cu % In %
1 0.1 0.01 0.1 0.01
1 0.1 0.02 0.1 0.02
1 0.1 0.03 0.1 0.03
1 0.1 0.04 0.1 0.04
1 0.1 0.05 0.1 0.05
1 0.3 0.01 0.3 0.01
1 0.3 0.02 0.3 0.02
1 0.3 0.03 0.3 0.03
1 0.3 0.04 0.3 0.04
1 0.3 0.05 0.3 0.05
Dopant amounts for double doping experiments
MATERIALS AND METHODS
LBO
Weight (g)
Cu % Ag % In %
1 0.1 0.04 0.01
1 0.1 0.04 0.03
1 0.1 0.04 0.05
1 0.1 0.05 0.01
1 0.1 0.05 0.03
1 0.1 0.05 0.05
1 0.3 0.04 0.01
1 0.3 0.04 0.03
1 0.3 0.04 0.05
1 0.3 0.05 0.01
1 0.3 0.05 0.03
1 0.3 0.05 0.05
Dopant amounts for triple doping experiments
RESULTS AND DISCUSSION-xrd-tl• X RAY DIFFRACTION high temperature solid state synthesis
a b
c
a) Undoped lithium tetraborate produced by high temperature solid state synthesis b) Lithium tetraborate doped by solid state doping method c) Lithium tetraborate doped by solution assisted doping method.
b
RESULTS AND DISCUSSION-xrd-tlUndoped lithium tetraborate produced by water assisted method b)Lithium tetraborate solution assisted doping
10 20 30 40 50 60 70 80
Inte
nsity (
arb
itra
ry u
nits)
2 degree)
• THERMOLUMINESCENCE ANALYSES
0 50 100 150 200 250 300 350 400 4500.0
2.0x104
4.0x104
6.0x104
8.0x104
1.0x105
Inte
nsi
ty (
arb
itra
ry u
nits
)
Temperature (oC)
0.1% Cu 0.2% Cu 0.3% Cu 0.4% Cu 0.5% Cu 0.6% Cu 0.7% Cu 0.8% Cu 0.9% Cu 1% Cu
H.T. Solid State Synthesized
Cu doped by H.T. Solid State
Very low intensity around 200oC
Very complicated glow curve , no noticable
trend
0 50 100 150 200 250 300 350 4000.0
5.0x104
1.0x105
1.5x105
2.0x105
2.5x105
3.0x105
3.5x105
4.0x105
4.5x105
5.0x105
Inte
nsi
ty (
arb
itra
ry u
nits
)
Temperature (oC)
Cu: 0.1% Cu: 0.2% Cu: 0.3% Cu: 0.4% Cu: 0.5% Cu: 0.6% Cu: 0.7% Cu: 0.8% Cu: 0.9% Cu: 1%
Water/Soln. Assisted
Synthesized
Cu doped by Solution Assisted
TechniqueHigher
intensity around 100oC
Around 200oCBest result:
0.1%Cu
0 50 100 150 200 250 300 350 4000.0
1.0x105
2.0x105
Inte
nsity (
arb
itra
ry u
nits)
Temperature (oC)
0.1% Cu 0.2% Cu 0.3% Cu 0.4% Cu 0.5% Cu 0.6% Cu 0.7% Cu 0.8% Cu 0.9% Cu 1% Cu
H.T. Solid State Synthesized
Cu doped by Solution Assisted
Technique
Lower intensity around 100oC
Main peak around 200oCBest result:
0.1%Cu
Glow patterns for the samples produced by solid state synthesis method and (0.1-1 % Cu) doped by solution assisted method.
Glow patterns for 0.1% Cu with varying amounts of Ag (0.01-0.05)
Glow patterns for 0.3% Cu with varying amounts of Ag (0.01-0.05)
with 0.1%Cu, 0.04% Ag coactivator gave the highest TL response.
Glow patterns for 0.1% and 0.3% Cu with varying amounts of In (0.01-0.05)
Glow patterns for 0.1% and 0.3% Cu-0.04%Ag with varying amounts of In (0.01-0.05)
with 0.1%Cu, 0.04% Ag coactivator gave the highest TL response.
XRD patterns of solution assisted synthesized undoped LTB (a), high temperature solid synthesized undoped LTB (b), solution assisted synthesized 1 wt % Mn doped LTB (c), and high temperature solid synthesized 1 wt % Mn doped LTB
0 10 20 30 40 50 60 70
b
c
dIn
tensity (a.u
.)
2 theta (degree)
a
Mn doping:
0 50 100 150 200 250 300 350 400 450-2000
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
temperature (°C)
0.1% Mn 0.5% Mn 1% Mn 2% Mn 3% Mn 4% Mn 5% Mn 6% Mn 7% Mn 8% Mn 9% Mn 10% Mn
inten
sity (
a.u.)
0 50 100 150 200 250 300 350 400 450
0
2000
4000
6000
8000
10000
12000
14000
0.1% Mn 0.5% Mn 1% Mn 2% Mn 3% Mn 4% Mn 5% Mn 6% Mn 7% Mn 8% Mn 9% Mn 10% Mn
inten
sity (
a.u.)
temperature (°C)
LTB synthesized with solution assisted method and solution assisted doped
LTB synthesized with solution assisted method and high temperature solid state doped
0 50 100 150 200 250 300 350 400 450
0
5000
10000
15000
20000
25000
0.1% Mn 0.5% Mn 1% Mn 2% Mn 3% Mn 4% Mn 5% Mn 6% Mn 7% Mn 8% Mn 9% Mn 10% Mn
inten
sity (
a.u.)
temperature (°C)0 50 100 150 200 250 300 350 400 450
0
20000
40000
60000
80000
0.1% Mn 0.5% Mn 1% Mn 2% Mn 3% Mn 4% Mn 5% Mn 6% Mn 7% Mn 8% Mn 9% Mn 10% Mn
temperature (°C)int
ensit
y (a.
u.)
LTB synthesized with high temperature solid state synthesis method and solution assisted doped
LTB synthesized with high temperature solid state synthesis method and high temperature solid state doped
0 50 100 150 200 250 300 350 400 450
0
10000
20000
30000
40000
50000
temperature (°C)
inte
nsity
(a.
u.)
0,1% Mn + 0,5% Ag 0,2% Mn + 0,5% Ag 0,3% Mn + 0,5% Ag 0,4% Mn + 0,5% Ag 0,5% Mn + 0,5% Ag 0,6% Mn + 0,5% Ag 0,7% Mn + 0,5% Ag 0,8% Mn + 0,5% Ag 0,9% Mn + 0,5% Ag 1,0% Mn + 0,5% Ag
Thermoluminescence measurements of LTB synthesized with high temperature solid state synthesis method and high temperature solid state doped with 0.5 wt % Ag and varying Mn content in the range of 0.1 - 1 wt %.
0 50 100 150 200 250 300 350 400 450
0
50000
100000
150000
200000
250000
300000
0,1% Mn + 0,5% P 0,2% Mn + 0,5% P 0,3% Mn + 0,5% P 0,4% Mn + 0,5% P 0,5% Mn + 0,5% P 0,6% Mn + 0,5% P 0,7% Mn + 0,5% P 0,8% Mn + 0,5% P 0,9% Mn + 0,5% P 1,0% Mn + 0,5% P
inte
nsity
(a.
u.)
temperature (°C)
Thermoluminescence measurements of LTB synthesized with high temperature solid state synthesis method and high temperature solid state doped with 0.5 wt % P and varying Mn content in the range of 0.1 - 1 wt %.
0 50 100 150 200 250 300 350 400 450 500 550
0
10000
20000
30000
40000
50000
60000
70000
temperature (°C)
inte
nsity (a.u
.) 0,1% Mn + 0,5% Mg 0,2% Mn + 0,5% Mg 0,3% Mn + 0,5% Mg 0,4% Mn + 0,5% Mg 0,5% Mn + 0,5% Mg 0,6% Mn + 0,5% Mg 0,7% Mn + 0,5% Mg 0,8% Mn + 0,5% Mg 0,9% Mn + 0,5% Mg 1,0% Mn + 0,5% Mg
Thermoluminescence measurements of LTB synthesized with high temperature solid state synthesis method and high temperature solid state doped with 0.5 wt % Mg and varying Mn content in the range of 0.1 - 1 wt %.
SEM images of solution assisted synthesized 1 wt % Mn solution assisted doped LTB (A), solution assisted synthesized 1 wt % Mn high temperature solid doped LTB (B), high temperature solid synthesized 1 wt % Mn solution assisted doped LTB (C), and high temperature solid synthesized 1 wt % Mn high temperature solid doped LTB (D).
TEM Micrograph taken from high temperature solid synthesized 1 wt % Mn high temperature solid doped LTB (A) and solution assisted synthesized 1 wt % Mn high temperature solid doped LTB (B).
CONCLUSIONSThe radii of Ag+ is larger than Li+ radius and LTB lattice will be destroyed, and therefore TL peaks are shifted.
Phosphorus co-doping increased the peak intensities of glow curves because when P is doped into LTB, PO4
3- can replace the BO4 units, the radius of P is not too larger than boron atom, no destruction in LTB lattice would be expected.
Electronegativity of P atom is higher than that of B atom, so impurity of P can produce electron traps in LTB crystals to enhance TL sensitivity.
Mg2+ has approximately same ionic radii with Li+ ions however, the high charge on Mg create great valance difference to destroy the LTB lattice.
High temperature solid state synthesis method is the way to combine highly ordered crystalline nanoparticles of the same phase because this method has diffusion control step of reactants. This step increases the time duration during crystallization.
In order to obtain high intensity glow peak the sample need to be the combinations of nano sized crystallites. Having bigger single crystals reduces the glow peak intensity of sample. Preparing lithium tetraborate by solution assisted synthesis method helps the formation of bigger single crystals.
Acknowledgements
Prof. Dr. Necmeddin Yazici, Dept. of Eng. Physics, University of Gaziantep,
National BORON Research Institute for financial support
References: 1.E. Pekpak, A. Yilmaz, G. Ozbayoglu, “The Effect of Synthesis and Doping Procedures on Thermoluminescent Response of Lithium Tetraborate” Journal of Alloys and Compounds, 509 (2011) 2466–2472.
2. M. Kayhan, A. Yilmaz, “Effects of Synthesis, Doping Methods and Metal Content on Thermoluminescence Glow Curves of Lithium Tetraborate“Journal of Alloys and Compounds, 509 (2011) 7818-7825.
Thank you very much for your attention!