1. S M Fuad Kabir Moni 1, Ö. Gün 1, H. J. Deiseroth 1. Introduction The Sensor Concept References Acknowledgements 1. E. GaudinI, H. J. Deiseroth, and T. ZaißII : The argyrodite g-Ag9AlSe6: A non-metallic filled Laves phase, Z. Kristallogr. 216 (2001) 39–44. 2.Shiao-Tong Kong, Hans-Jörg Deiseroth, Christof Reiner, özgul Gün, Elmar Neumann, Clemens Ritter and Dirk Zahn : Lithium Argyrodites with Phosphorus and Arsenic:Order and Disorder of Lithium Atoms, Crystal Chemistry, and Phase Transitions, Chem. Eur. J. 2010, 16, 2198 – 2206 3.Shiao-Tong Kong, Özgul Gün, Barbara Koch, Hans-Jörg Deiseroth, Hellmut Eckert, Christof Reiner : Structural Characterisation of the Li Argyrodites Li 7 PS 6 and Li 7 PSe 6 and their Solid Solutions: Quantification of Site Preferences by MAS-NMR Spectroscopy, Chem. Eur. J. 2010, 16, 5138 – 5147 SAMPLE PREPARATION AND CHARACTERIZATION OF MIXED Li-Cu ARGYRODITES 2. Argyrodites Argyrodites are good ionic conductor and also used as a solid state electrolyte in a battery to increase its life. The researchers are trying develop long time power backup of a battery using new electrolytes. Using the mixed crystal argyrodites as an electrolytes is the most important steps for further innovation of the durable battery. 4. Relation Between Cubic Laves Phase and Argyrodite Structure 3. Synthetic argyrodites 5. Phase transition of Argyrodites. Mobility 1) Inorganic Chemistry I, Department Chemistry-Biology, University of Siegen, Adolf-Reichwein-Str.2, 57076 Siegen, Germany. Silver (Ag) = 76.51 % Germanium (Ge) = 6.44 % Sulfur (S) = 17.06 % Fig 1: Natural Argyrodites (Ag 8 GeS 6 ) Clemens Alexander Winkler 1886 1. Motivation 1.Ternary Argyrodites A m+ (12-n)/m B n+ Ch 6 2- 2. Quaternary Argyrodites A m+ (12-n-x)/m B n+ Ch 6-x 2- X x - A = A + (Ag, Cu, Li) A 2+ (Cd, Hg) B = B 3+ (Ga, Al) B 4+ (Si, Ge, Sn) B 5+ (P, As) Ch = O, S, Se, Te X = Cl, Br, I (0 ≤ x ≤ 1) i.e. Ag 7 PSe 6, Ag 8 GeSe 6, Cu 7 PSe 6 i.e. Ag 7 GeSe 5 I Crystal Structure of Argyrodites Synthesis of mixed Argyrodite δ = 0 to 7 Reaction condition Heating rate :20 0 C per hour till 600 0 C Reaction time at 600 0 C is 120 hours. Cooling rate : 20 0 C per hour. Cubic Laves Phase Argyrodite E. Gaudin, H. J. Deiseroth and T. Zaiß, Z. Kristallogr. 216 (2001) 39–44 Frank Kasper Polyhedra C.N. = 12 C.N. = 15 C.N. = 14 C.N. = 16 MgCu 2 (Fd3m) Ag 9 AlSe 6 (F-43m) δ Li 2 Se + (7- δ)Cu 2 Se + P 2 Se 5 2Li δ Cu (7- δ) PSe 6 600 0 C Compounds Cu 7 PSe 6 LiCu 6 PSe 6 Li 2 Cu 5 PSe 6 Li 3 Cu 4 PSe 6 Li 4 Cu 3 PSe 6 Li 5 Cu 2 PSe 6 Li 6 CuPSe 6 Li 7 PSe 6 Tetrahedral Close Packing Total 136 Tetrahedra Only 4 of them occupied by P Rest occupied by Li in disordered way. Characterization ArgyroditesCrystal SystemSpace Group Lattice Constant (Å) Cell volume/Å 3 Cu 7 PSe 6 CubicP213P21310.14671034.28 LiCu 6 PSe 6 OrthorhombicPna2 1 a = 14.4531 b = 10.1390 c = 7.1744 1051.34 Li 2 Cu 5 PSe 6 CubicF-43m10.217051066.53 Li 3 Cu 4 PSe 6 CubicF-43m10.252691077.74 Li 4 Cu 3 PSe 6 CubicF-43m10.289811089.49 Li 5 Cu 2 PSe 6 CubicF-43m10.32881101.95 Li 6 CuPSe 6 CubicF-43m10.36361112.97 Li 7 PSe 6 OrthorhombicPna2 1 a = 14.5486 b = 10.4746 c = 7.3853 1125.45 LiCu 6 PSe 6 Li 3 Cu 4 PSe 6 ArgyroditesElementsCalculated (atom %)Measured (atom %) Cu 7 PSe 6 Cu P Se 50 7.14 42.86 48.70 8.78 42.52 LiCu 6 PSe 6 Cu P Se 46.14 7.69 46.14 48.03 4.52 48.03 Li 3 Cu 4 PSe 6 Cu P Se 36.36 9.09 54.54 25.36 13.04 61.60 Li 7 PSe 6 P Se 14.28 85.72 10.79 89.21 Conclusion All solid state lithium ion batteries are attractive power sources for the many electrochemical applications, due to their potentiality in terms of improving safety and stability over the conventional batteries with the liquid electrolytes. Contemporary all lithium ion batteries require a Li fast ion conductor as a solid electrolyte. It is a big challenge to find out a suitable solid electrolyte of the Li-ion with high ionic conductivity and performance of the Li-ion battery. There have been numerous research on Li-rich sulfide glasses as a solid state electrolytes, but they showed limited current density. To avoid this major drawback a new class of material called argyrodites (ternary and quaternary) have been introduced as a solid state electrolyte. The quaternary argyrodite showed better stability in oxidation- reduction but lower conductivity at room temperature compare to the ternary argyrodites. The characteristics of a mixed argyrodites (more than one conductive element) in terms of stability and conductivity is still unknown. This project is focused on the synthesis and characterization of a series of Li and Cu based mixed ternary argyrodites. The air-sensitive products were prepared in a glovebox. The samples were ground and loaded with grease (Lithelen) between two Mylar foils (diameter: 0.1 mm). The diffraction data were collected on a Siemens D5000 diffractometer (CuKa1 radiation, Ge monochromator). The data analyses were performed by using the STOE Software package WINXPOW Powder X-ray measurements Microstructure analysis by SEM and EDX Fig : Comparing MgCu 2 (Fd3m) Vs Ag 9 AlSe 6 (F-43m) Fig: Different Frank Kasper polyhedra according to CN Fig : Tetrahedral holes with packing with Li The granulated compounds were transferred in tubes of boran glass and temporary seal with grease to protect from air outside the globe box and again seal with the help of H 2 -O 2 flame. Due to dark colour samples, it was very difficult to get better intensities. Raman analysis Fig: Microstructure images from the SEM for different compounds. Fig : Spectrum from EDX for argyrodites Table: Comparing atomic percentages from calculated and from EDX Fig: Raman spectrum for Li 0 to Li 7 DTA analysis Differential scanning calorimetry measurements were performed on samples in stainless steel crucibles under a nitrogen atmosphere between 143 and 873 K with a heating rate of 7 Kmin1 by using a Setaram DSC131. The preparation of the sealed crucible was carried out in an argon-filled glovebox. Differential thermal analyses were carried out in evacuated graphitised quartz ampules between room temperature and 673 K with a heating rate of 5 Kmin1 by using a DTA-L62 (Linseis company). Fig: Sections of the DTA curve of Li 7 PSe 6 Fig: X-ray powder diagrams of Li 7 PSe 6 before (black) and after (red) DTA measurements. EDX (energy dispersive X-ray) analysis was used to semi-quantitatively (Li disregarded) check the ratio of phosphorus/sulfur/ selenium and to prove the absence of silicon (quartz glass ampoule), which is important due to the existence of silicon-containing argyrodites. A joint probability density function (jpdf) to visualize the delocalization of silver atoms in the framework. Calculating the jpdf of silver atoms gives evidence for the diffusion pathway of the silver atoms in the structure. Fig: Three-dimensional representation of a joint probability density isosurface (at the 150 A –3 level) for g-Ag9AlSe6 at 293 K, showing the silver diffusion path around the Se2 atom. The characterization of the Li-Cu mixed argyrodites sample have been investigated in PD, EDX, Raman and SEM at room temperature. The single crystal investigation, solid state NMR and conductivity by impedence spectroscopy currently under investigation to compare with the properties with other ternary and quaternary argyrodites.