1. Assoc. Prof. Dr. Ayşen YILMAZ Department of Chemistry Middle East Technical University Ankara, TURKEY Prof. Dr. Gülhan ÖZBAYOĞLU Dean Faculty of Engineering Atılım University Ankara, Turkey RAD, 24-27 April 2012

2. OBJECTIVES To synthesize metal doped Li 2 B 4 O 7 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.

3. THERMOLUMINESCENCE HEATING LIGHT EMISSION RADIATION EXPOSURE AND RESULTANT RADIATION STORAGE

4. 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 1150 o C) rapid cooling employed  Crystal: require complicated systems, seed crystal

5. LITHIUM TETRABORATE TL RESPONSE ▫ Glow Curve: Generally around 200 O C

6. MATERIALS AND METHODS 2- METHODS Li 2 CO 3 + 4H 3 BO 3  Li 2 B 4 O 7 + CO 2 +6 H 2 O Doping Synthesis Method Material Li 2 B 4 O 7 High Temp. Solid State High Temp. Solid State Solution Assisted Water /Solution Assisted Solution Assisted

7. MATERIALS AND METHODS Mixing Stoichiometric quantities of Li 2 CO 3 and H 3 BO 3 Initial Heating 0-400 o C by 400 o C per hr Retention Time: 3 hr Mixing,Pounding, Blending 0-400 o C by 400 o C per hr Retention Time: 3 hr Mixing,Pounding, Blending Secondary Heating Secondary Heating 400-750 o C by 400 o C per hr 2 hr exposure Intermittent mixing 2 more hours 400-750 o C by 400 o C per hr 2 hr exposure Intermittent mixing 2 more hours High Temperature Solid State Synthesis

8. MATERIALS AND METHODS Water / Solution Assisted Synthesis Stirring Li 2 CO 3 and H 3 BO 3 in 15 ml water At 100-150 o C for 15-20 min Li 2 CO 3 and H 3 BO 3 in 15 ml water At 100-150 o C for 15-20 min Initial Heating 0-150 o C by 400 o C per hr Retention Time: 3 hr Mixing 0-150 o C by 400 o C per hr Retention Time: 3 hr Mixing Secondary Heating Secondary Heating 400-750 o C by 400 o C per hr 4 hr exposure 400-750 o C by 400 o C per hr 4 hr exposure

9. 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  25-750 o C by 400 o C per hr  Retention  2+1 hr with intermittent mixing

10. MATERIALS AND METHODS Solution Assisted Doping  For 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  150 o C - 3 hrs, 700 o C - 2 hrs

11. MATERIALS AND METHODS LBO Weight (g)Cu %Ag %Cu %In % 10.10.010.10.01 10.10.020.10.02 10.10.030.10.03 10.10.040.10.04 10.10.050.10.05 10.30.010.30.01 10.30.020.30.02 10.30.030.30.03 10.30.040.30.04 10.30.050.30.05 Dopant amounts for double doping experiments

12. MATERIALS AND METHODS LBO Weight (g) Cu %Ag %In % 10.10.040.01 10.10.040.03 10.10.040.05 10.10.050.01 10.10.050.03 10.10.05 10.30.040.01 10.30.040.03 10.30.040.05 10.30.050.01 10.30.050.03 10.30.05 Dopant amounts for triple doping experiments

13. 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.

14. b RESULTS AND DISCUSSION-xrd-tl Undoped lithium tetraborate produced by water assisted method b)Lithium tetraborate solution assisted doping

15. THERMOLUMINESCENCE ANALYSES H.T. Solid State Synthesized Cu doped by H.T. Solid State Very low intensity around 200 o C Very complicated glow curve, no noticable trend

16. Water/Soln. Assisted Synthesized Cu doped by Solution Assisted Technique Higher intensity around 100 o C Around 200 o C Best result: 0.1%Cu

17. H.T. Solid State Synthesized Cu doped by Solution Assisted Technique Lower intensity around 100 o C Main peak around 200 o C Best result: 0.1%Cu

18. Glow patterns for the samples produced by solid state synthesis method and (0.1-1 % Cu) doped by solution assisted method.

19. 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.

20. Glow patterns for 0.1% and 0.3% Cu with varying amounts of In (0.01-0.05)

21. 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.

22. 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 Mn doping:

23. LTB synthesized with solution assisted method and solution assisted doped LTB synthesized with solution assisted method and high temperature solid state doped

24. 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

25. 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 %.

26. 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 %.

27. 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 %.

28. 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).

29. 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).

30. CONCLUSIONS The 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, PO 4 3- can replace the BO 4 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. Mg 2+ 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.

31. 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!