The material system YMn₂O₅ has several low temperatures phases, where magnetism and ferroelectricity occur. Especially, the origin of the ferroelectricity (FE) in a phase below T_FE = 39 K is an open question. The Literature agrees upon a magnetically driven principal mechanism from changes in the Mn spin configuration, which may be based either on magnetostriction due to symmetric exchange, the antisymmetric inverse Dzyaloshinskii-Moriya interaction or a combination of the two. Both mechanisms are accompanied by specific atomic displacements of ions in the structure. The space group Pbam (55) of the paraelectric phase does not allow the respective polar displacements and a refinement of the charge structure in a lower symmetric phase has not been successful so far, as the applied conventional structure analysis methods lack the required spatial resolution for the expected positional deviations.

We apply the new Resonantly Suppressed Diffraction (RSD)³ method, which is sensitive to minuscule structural changes in the sub-pm range, to shed new light on this controversial discussion. RSD is a structural characterization method in the field of Resonant Elastic X-ray Scattering and tunes the photon energy such that certain reflections approach zero due to destructive interference.

Here, we employ RSD on carefully chosen Bragg reflections below and above T_fE. With the data above T_FE we refined the static and dynamic displacements of the paraelectric phase, to receive an improved starting model for the structural characterization of the FE phase. With this starting model we were able to characterize the FE phase and consolidating the findings about the origin of ferroelectricity in YMO.

³Richter, C., Zschornak, M., Novikov, D. V., Mehner, E., Nentwich, M., Hanzig, J., Gorfman,S. & Meyer, D. C. Nature Communications, 9, 178 (2018).

Breast cancer is the leading cause of cancer death in women worldwide. Systemic changes in the elemental composition of the microenvironment between the cancer cells and the host stroma play an important role in supporting the growth and progression of the tumor. Excessive accumulation of the trace elements Fe, Zn, and Cu and its relationship with the matrix of the tumor microenvironment remodeling has been reported. Although the knowledge of breast carcinogenesis is being progressively elucidated with 2D cell-culture experiments, they are not able to reproduce the real physiological pattern of the tumor microenvironment where the surroundings cells are equally as important as the tumor cell itself. X-ray fluorescence (XRF) has been successfully exploited to detected trace elements in breast tissues, nevertheless, this technique is not sensitive to light elements such as carbon and oxygen, the major constituents of the breast tissue matrix. This information can be complemented by using the Rayleigh-to-Compton ratio technique (R/C). Likewise, the microenvironment remodeling comprises collagen fibrils rearrangements which can be investigated by Small-angle X-ray scattering (SAXS). Therefore, it will be shown the results of a pilot experiment exploiting the complementarity of the X-ray scattering and spectroscopy signals tomographically acquired, to map three-dimensionally the changes due to cancer progression.

Refractory materials structural and surface changes by sulfuric acid treatment E. Nushi¹, L. Gjurgjaj², A. Mele^1,21Center of Techniques Studies, Ivodent Academy, Rr. “Prokop Myzeqari, nr.10, Tirana, Albania enida.nushi@ivodent.org altin.mele@ivodent.edu.al ²Department of Chemistry, Faculty of Natural Sciences, University of Tirana, Bulevardi “Zog I”, nr. 25/1, 1016-Tirana, Albania lorenci.gjurgjaj@fshnstudent.info

Prrenjas clay mineral is used as refractory material in the metal casting and is found in southeast of Albania. It has a high content on bentonite. The influence of the sulphuric acid activation on the composition, structure and surface properties of Prrenjas clay mineral is investigated in this study by means of elemental chemical analysis, X-Ray Diffractometry, IR Spectroscopy and gas adsorption-desorption measurement. H₂SO₄ concentrations of 0.143 M, 0.232 M, 0.371 M, 0.537 M, 0.734 M, 0.927 M and 1.456 M were used in the treatment of samples. The treatment by increasing the acid concentration brings the leaching of Al³⁺, Fe²⁺, Mg²⁺ from the clay structure. The specific surface area and the pore volume of the clay samples increases respectively from 83 m²/g and 0.069 cm³/g for the untreated clay to 420 m²/g and 0.384 cm³/g for the clay mineral treated with 1.456 M H₂SO₄ solution. New mesopores were created during the acid activation mainly in the range of 2 – 8 nm. For the samples treated with 0.927 M and 1.456 M solutions the increase in specific surface area and pore volume is very high. The cationic exchange capacity decreases steadily with the concentration of H₂SO₄ used for the treatment.

[1]Steudel, A., Batenburg, L. F., Fischer, H. R., Weidler, P. G., Emmerich, K. (2009). Appl. Clay Sci. 44, 105-115.[2] Komadel, P., Schmidt, D., Madejova, J., Cicel, B. (1990). Appl. Clay Sci. 5, 113-122.[3]Madejova, J., Budjak, J., Janek, M., Komadel, P. (1998) Spectrochim. Acta 54, 1397-1406.[4] Kahr, G., Madsen, F. T. (1995). Applied Clay Sci., 9, Alexandre, 327-336.

Keywords: clay mineral; acid activation; surface properties

The present work is based on the development of a new lead-free perovskite system (Ba_1-xCa_x)(Sn_0.11Zr_0.05Ti_0.84)O₃ (BCSZTx); 0≤x≤0.20, exhibiting ferroelectricity in an average cubic structure [1]. The x-ray diffraction measurements have shown a simple cubic phase with Pm-3m space group for all the compositions. Despite having a centrosymmetric cubic phase, a slim hysteresis loop has been observed via PE loop measurements. Raman spectroscopic measurements have revealed the presence of local ordering in the macroscopically cubic matrix, corresponding to ‘A’ and ‘B’ sites. The cooperative behaviour of ‘A’ and ‘B’ site off-centered (local) atoms leading to microscopic polar symmetry in the macroscopically cubic matrix is held responsible for the observed ferroelectricity [2-4]. Owing to the aforementioned contrapositive behaviour, these ceramics have shown a diffuse dielectric phase transition with relaxor nature and thus exhibit a high value of dielectric constant. Eventually, we have clearly observed a decisive role of Ca²⁺ dopant at ‘A’ site in BCSZTx ceramic system leading to the enhancement in the ferroelectric and dielectric properties. The presence of a slim hysteresis loop along with broad and diffuse dielectric nature makes these ceramics a potential candidate for energy storage applications.

References:

[1] Y. Yao, C. Zhou, D. Lv, D. Wang, H. Wu, Y. Yang, and X. Ren, EPL (Europhysics Letters) 98, 27008 (2012).

[2] D. Fu, M. Itoh, S.-y. Koshihara, T. Kosugi, and S. Tsuneyuki, Physical review letters 100, 227601 (2008).

[3] A. K. Singh, D. N. Dubey, G. Singh, and S. Tripathi, EPL (Europhysics Letters) 130, 36002 (2020).

[4] V. Buscaglia, S. Tripathi, V. Petkov, M. Dapiaggi, M. Deluca, A. Gajovic, and Y. Ren, Journal of Physics: Condensed Matter 26, 065901 (2014).

The (E)-N-benzylidene-4-haloanilines belong to the Schiff base family, an important class of organic compounds which appears as an intermediate in several biological processes and during synthesis of organic compounds, due to the presence of azomethine group it finds extensive applications in analytical, coordination chemistry and biochemistry[1]. Some patents included versatile applications of this type of compounds, for example, in the protection of the skin against the harmful effects caused by sun exposure (Erythema), as well as the importance of mixtures of N-benzylideneanilines with aqueous acid solutions used as anticorrosives[2].The use of organic solvents translates into a significant environmental cost, which is why synthetic methods have been developed that do not involve solvents and involve other principles of green chemistry; the clean and efficient preparation of imines in aqueous suspension is one of them, in which acid catalysis is not necessary and provides relatively high yields when 1: 1 mixtures of aromatic aldehydes are reacted with primary aromatic amines[3]

In the X-ray powder diffraction crystallography literature, there are still no records for the resolution of the structure of the (E)-N-benzylidene-4-fluor(chloride)aniline, although for the other two haloanilines there are available data obtained in a previous work made by a former undergraduate student. The resolution of the structures was made using a D8 ADVANCE with DaVinci geometry, these data, as well as the other different spectroscopic results will be exposed and discussed in the poster.

In this work, the results obtained by single X-ray diffraction (XRD); even if for larger R-factor, are confirmed by another independent technique, one can study the vibrational spectroscopy with symmetry and group theory character tables. This method can be applied on the whole molecule or a part of it, mainly we search for function groups such as H₂O, an ionic part such as NH⁴⁺ or metal halide such as (MnBr_x). The fine XRD data results five possible solutions for the same molecule with the same chemical formula, although the R-factor values are so close, this method can distinguish between these possible solutions upon the crystal structure. The study of C₅H₁₀(NH₃)₂(MnCl₄Br₂) results one solution of XRD is confirmed by IR and Raman spectroscopy.

The space group of the molecule Ima2 with R= 3.33, The (MnCl₄Br₂) belongs to D_4h of 5 Raman peaks and different 5 IR peaks.

The Mn₂(MnCl₄Br₂) is C₂, C_2h or C_s according To the location of Mn atoms to the octahedral, the suitable solution is C_2h which expects 12 IR and another 9 Raman peaks with good agreement with IR and Raman results.

References

1. J. R. Ferraro, "Low-Frequency Vibrations of Inorganic and Coordination Compounds", Plenum Press, New York (1971).
2. M. S. Dresselhaus G. Dresselhaus and A. Jorio. Group theory: Application to the physics of condensed matter (Springer, Berlin, Germany, 2008) CH8.
3. G. Herzberg. Molecular spectra & molecular structure: II Infrared & Raman spectra of polyatomic molecules (Von Nostrand Reinhold comp., New York, USA, 1945) pp. 462-487.
4. K. Kamaras, L. Badeeb, M. Özeren, A. Pekker, S. Abdel-Aal, A. S. Abdel-Rahman, P. Andricevic, L. Forro and E. Horvath, Bulletin of the American Physical Society, MARV20013K (2019).
5. S. K. Abdel-Aal, A. S. Abdel-Rahman, W. M. Gamal, M. Abdel-Kader, H. S. Ayoub, A. F. El-Sherif, M. Fawzy, S. Bozhko, E. E. Yakimov and E. B. Yakimov, Acta Crystallographica B75(5) 880-886 (2019).