RARE EARTHS CHEMISTRY: SCIENTIFIC, TECHNOLOGICAL AND PRODUCTION ACTIVITIES AT THE DEPARTMENT OF INORGANIC CHEMISTRY, SOFIA UNIVERSITY

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THE DEPARTMENT OF INORGANIC CHEMISTRY, SOFIA UNIVERSITY M. Milanova, D. Todorovsky, N.

1 Group of Rare and Rare Earth Elements, Est RARE EARTHS CHEMISTRY: SCIENTIFIC, TECHNOLOGICAL AND PRODUCTION ACTIVITIES AT THE DEPARTMENT OF INORGANIC CHEMISTRY, SOFIA UNIVERSITY M. Milanova, D. Todorovsky, N. Minkova, A. Terziev, M. Getsova, G. Tzvetkov, N. Petrova, M. Uzunova, S. Anastasova, J. Zaharieva, R. Kralchevska, R. Todorovska

2 Chemistry of rare earth elements SOLID SOLUTIONS COORDINATION COMPOUNDS MECHANOCHEMISTRY Leaching, separation, purification RE products Materials, based on REE Silicates Polymetallic oxides Modified photocatalysts Thin films Optical sensors

3 Plan Materials based on REE RE products

4 Polymerized complex method, PCM

5 Polymerized complex method Problems Reaction CA /EG Factors influencing the complex compositions Nature of the complexes in bimetallic systems Alcoholic group deprotonation Thermochemical behaviour of the complexes; nature of the final precursor Application of the solutions of complexes for thin film deposition

6 Synthesized and characterised materials Buffer layers for high temperature superconductors (Y 2 O 3, CeO 2, YSZ) Materials of high magnet restriction (LaMnO 3, pure/doped with Ca) Magnet materials (Fe 2 O 3, Y 3 Fe 5 O 12, (granite), YFeO 3, Y 3 Fe 5 O 12 doped with Al or Се) Ferroelectrics ( La 2 Ti 2 O 7, Nd 2 Ti 2 O 7 ) Ionic conductors (Y 2 Ti 2 O 7 ) Oxygen sensors based on YSZ, doped with Pt nanoparticles (Assoc. Prof. Dimitrov, Assoc. Prof. Dushkin) Optical oxygen sensors Photocatalysts based on TiO 2, including modified by doping with Lа or by mechanochemical treatment (Assoc. Prof. Dimitrov)

7 Deposition of thin films Spray-pyrolysis /PCM (mixed-metal citrates)

fused quarz SEM images (8 mol% Y) Т substrate 350 o C;

8 Thin films of Y-stabilized ZrO 2 Buffer layers for high temperature superconductors (YBCO) XRD film on quarz On fused quarz SEM images (8 mol% Y) Т substrate 350 o C; additionally annealed at 750 о С On glass film on fused silica powder

Thin films of CeO 2 Buffer layers for high

9 Thin films of CeO 2 Buffer layers for high temperature superconductors AFM (10x10 μm), from Ce(N)Cit (fused quarz) AFM (5x5 μm), from Ce(Cl)Cit (fused quarz) from Ce(N)Cit, Т substrate 500 о С from Ce(N)Tar Т substrate 350 о С size of the grains ( )x( ) nm

10 Thin films of LaMnO 3 Materials of high magnet restriction AFM (6,5x6,5 μm) of LaMnO 3 film on SrTiO 3 La 0,7 Ca 0,3 MnO 3 LaMnO 3 SEM of manganite films with thickness ~150 nm on SrTiO 3, x20 000). XRD

11 Thin films of YFeO 3 Ferromagnetic behaviour, potential UV-Vis photocatalyst AFM (5x5 μm) of YFeO 3 film on SrTiO 3

12 Thin films of La-doped TiO 2 Photocatalysts glass graphite stainless steel SEM images, post deposition heating at 400ºC (a), 500ºC (b,c). Ti-coated steel Degradation of methylene TiO 2 :5 mol% La blue, silica

13 Thin films based on SiO 2 Optical oxygen sensors Silanes Ru(dpp) 3 2+ Tetraethoxy silane (TEOS) Methyl triethoxysilane (MTEOS) I 0 = 1 + К SV O I [ ] 2 Octyl-triethoxysilane (OtEOS)

14 SiO 2 -based films Effect of sonication Stern-Volmer constants (n.10-3 % -1 ) Gas phase Water 0 TEOS TEOS + OtEOS TEOS + MtEOS TEOS TEOS + OtEOS TEOS + MtEOS No sonication Sonication

15 PMMA films Optical oxygen sensors SEM PMMA solution AFM PMMA solution MMA polymerized

16 PMMA films Oxygen in the gas phase I 0 /I 2,0 Ksv = 0,0105 1,5 1,0 0,5 I 0 /I 2,0 1,5 1,0 0,5 Ksv = 0,0017 0, Concentration of O 2, % 1 0, Concentration of O 2, % film prepared via PMMA solution film prepared via in situ polymerization of MMA

17 PMMA films Dissolved oxygen in water 1,3 1,2 KSV=0,0062 I 0 /I 1,1 1,0 0, Concentration O 2, ppm film prepared via PMMA solution

18 Hybrid matrix, SiO 2 /polyester Optical oxygen sensors TEOS/CA/EG = 4 : 1 : 1

19 Hybrid matrix, SiO 2 /polyester I 0 /I Oxygen in the gas phase Ksv =0,0302 Intensity, a. u. 1,0 0,8 0,6 0,4 Oxygen dissolved in water Ksv 0, , Concentration of O 2 0, Concentration of O 2, ppm

20 K sv, comparison Ksv Gas Water PMMA MMA Hybrid

21 Eu β-diketonates Immobilization in PMMA matrix DBM

Eu(DBM) 3 oxygen sensitive AFM AFM,, Eu(DBM) 3 in 3 in PMMA 80 450 70 400 Intensity, a. u.

22 Eu(DBM) 3 oxygen sensitive AFM AFM,, Eu(DBM) 3 in 3 in PMMA Intensity, a. u μs Powder Intensity, a. u μs Immobilized in matrix Wavelenght, nm Wavelength, nm

23 AFM, Eu(DBM) 3.phen in PMMA Eu(DBM) 3.Phen Phen 1,10-phenathroline Intensity, a.u μs Powder 400 Intensity, a. u μs Immobilized in matrix Wavelength, nm Wavelength, nm

24 REE products, Technology and production activities Methods of RE recovery from waste and by-products Production routes for some RE compounds developed and carried out in practice

25 RE sources Phosphogypsum H 3 PO 4 Mechanochemical treatment RE concentrate Ca separation RE concentrate, low Ca REO non-re sepn

26 REO treatment Ce separation Mechanochemistry Selective dissolution Selective precipitation CeO 2 Ln 2 O 3

27 REO/Ln 2 O 3 REO Ln 2 O 3 Extraction La-Nd Didymium Heavy RE, Eu LME Solid state complexes, DEHPA Nd 2 O 3 Pr concentrate Concentrate, Eu enriched La 2 O 3 Eu 2 O 3

28 Pilot facilities

29 Some of the products Product REE yield, % Purity REE concentrate of low Са content 99 Са<1,5% RE oxide mixture % СеО Ln 2 O 3 : < 10-2 %, other impurities: < 0.1% Oxide mixture, Се-free Се < 1,5% Nd 2 O % % Eu 2 O % % Y 2 O % Y 2 O 3 (from YAG) 85 Impurities of Аl Polishing material 85 Cerox quality

30 Thank you! Dr. Maria Milanova, Assoc. Prof., nhmm@wmail.chem.uni-sofia.bg

Supplementary Figure 1. Substrate X-ray diffraction patterns Supplementary Figure 2. Substrate XPS.

$Supplementary Figure 1. Substrate X-ray diffraction patterns Supplementary Figure 2. Substrate XPS.$ Supplementary Figure 1. Substrate X-ray diffraction patterns. Patterns show the main rutile peaks, but only very weak Au peaks from the AuNPs (gold nanoparticles). The top pattern was collected after irradiation