Roxana Elena Patru
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Scopus Publications
Scholar Citations
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Scopus Publications
R.E. Pătru, C.A. Stanciu, V.A. Surdu, E.M. Soare, R.D. Truşcă, B.S. Vasile, A.I. Nicoară, L. Trupină, I. Pasuk, M. Botea,et al.
Elsevier BV
Vasile-Adrian Surdu, Mariana-Andreea Marinică, Roxana-Elena Pătru, Ovidiu-Cristian Oprea, Adrian Ionuț Nicoară, Bogdan Ștefan Vasile, Roxana Trușca, and Adelina-Carmen Ianculescu
MDPI AG
A novel high-entropy perovskite powder with the composition Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 was successfully synthesized using a modified Pechini method. The precursor powder underwent characterization through Fourier Transform Infrared Spectroscopy and thermal analysis. The resultant Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 powder, obtained post-calcination at 900 °C, was further examined using a variety of techniques including X-ray diffraction, Raman spectroscopy, X-ray fluorescence, scanning electron microscopy, and transmission electron microscopy. Ceramic samples were fabricated by conventional sintering at various temperatures (900, 950, and 1000 °C). The structure, microstructure, and dielectric properties of these ceramics were subsequently analyzed and discussed. The ceramics exhibited a two-phase composition comprising cubic and tetragonal perovskites. The grain size was observed to increase from 35 to 50 nm, contingent on the sintering temperature. All ceramic samples demonstrated relaxor behavior with a dielectric maximum that became more flattened and shifted towards lower temperatures as the grain size decreased.
Vladimir Lucian Ene, Valentin Razvan Lupu, Claudiu Vasile Condor, Roxana Elena Patru, Luminita Mirela Hrib, Luminita Amarande, Adrian Ionut Nicoara, Lucian Pintilie, and Adelina-Carmen Ianculescu
MDPI AG
Fine-tuning of grain sizes can significantly influence the interaction between different dielectric phenomena, allowing the development of materials with tailored dielectric resistivity. By virtue of various synthesis mechanisms, a pathway to manipulate grain sizes and, consequently, tune the material’s dielectric response is revealed. Understanding these intricate relationships between granulation and dielectric properties can pave the way for designing and optimizing materials for specific applications where tailored dielectric responses are sought. The experimental part involved the fabrication of dense BCT-BZT ceramics with different grain sizes by varying the synthesis (conventional solid-state reaction route and sol-gel) and consolidation methods. Both consolidation methods produced well-crystallized specimens, with Ba0.85Ca0.15O3Ti0.9Zr0.1 (BCTZ) perovskite as the major phase. Conventional sintering resulted in microstructured and submicron-structured BCT-BZT ceramics, with average grain sizes of 2.35 μm for the solid-state sample and 0.91 μm for the sol-gel synthesized ceramic. However, spark plasma sintering produced a nanocrystalline specimen with an average grain size of 67.5 nm. As the grain size decreases, there is a noticeable decrease in the maximum permittivity, a significant reduction in dielectric losses, and a shifting of the Curie temperature towards lower values.
Roxana-Elena Pătru, Cătălina Andreea Stanciu, Elena Mirabela Soare, Vasile-Adrian Surdu, Roxana Doina Truşcă, Adrian Ionuţ Nicoară, Bogdan Ştefan Vasile, Georgia Boni, Luminiţa Amarande, Nadejda Horchidan,et al.
Elsevier BV
Nicolae Filipoiu, Amanda Teodora Preda, Dragos-Victor Anghel, Roxana Patru, Rachel Elizabeth Brophy, Movaffaq Kateb, Cristina Besleaga, Andrei Gabriel Tomulescu, Ioana Pintilie, Andrei Manolescu,et al.
American Physical Society (APS)
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Andra Georgia Boni, Roxana Patru, Lucian D. Filip, Cristina Chirila, Iuliana Pasuk, Ioana Pintilie, and Lucian Pintilie
American Chemical Society (ACS)
Roxana Patru, Hamidreza Khassaf, Iuliana Pasuk, Mihaela Botea, Lucian Trupina, Constantin-Paul Ganea, Lucian Pintilie, and Ioana Pintilie
MDPI AG
The frequency and temperature dependence of dielectric properties of CH3NH3PbI3 (MAPI) crystals have been studied and analyzed in connection with temperature-dependent structural studies. The obtained results bring arguments for the existence of ferroelectricity and aim to complete the current knowledge on the thermally activated conduction mechanisms, in dark equilibrium and in the presence of a small external a.c. electric field. The study correlates the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes, as well as with the different transport regimes indicated by the Nyquist plots. The different energy barriers revealed by the impedance spectroscopy highlight the dominant transport mechanisms in different frequency and temperature ranges, being associated with the bulk of the grains, their boundaries, and/or the electrodes’ interfaces.
Andrei Gabriel Tomulescu, Lucia Nicoleta Leonat, Florentina Neațu, Viorica Stancu, Vasilica Toma, Sarah Derbali, Ștefan Neațu, Arpad Mihai Rostas, Cristina Beșleagă, Roxana Pătru,et al.
Elsevier BV
Mihaela Botea, Ioana Pintilie, Vasile-Adrian Surdu, Cătălina-Andreea Stanciu, Roxana-Doina Truşcă, Bogdan Ştefan Vasile, Roxana Patru, Adelina-Carmen Ianculescu, and Lucian Pintilie
Elsevier BV
Felicia Gheorghiu, Roxana Stanculescu, Lavinia Curecheriu, Elisabetta Brunengo, Paola Stagnaro, Vasile Tiron, Petronel Postolache, Maria Teresa Buscaglia, and Liliana Mitoseriu
Springer Science and Business Media LLC
Roxana Elena Patru, Constantin Paul Ganea, Catalina-Andreea Stanciu, Vasile-Adrian Surdu, Roxana Trusca, Adelina-Carmen Ianculescu, Ioana Pintilie, and Lucian Pintilie
Elsevier BV
Vlad Alexandru Lukacs, Roxana Stanculescu, Lavinia Curecheriu, Cristina Elena Ciomaga, Nadejda Horchidan, Cipriana Cioclea, and Liliana Mitoseriu
Elsevier BV
Roxana Stanculescu, Nadejda Horchidan, Carmen Galassi, Mihai Asandulesa, Leontin Padurariu, Cristina Ciomaga, and Liliana Mitoseriu
National Library of Serbia
3D Finite Element Method simulations were employed in order to describe tunability properties in anisotropic porous paraelectric structures. The simulations predicted that properties of a ceramic can be tailored by using various levels of porosity. Porous Ba0.6Sr0.4TiO3 (BST) ceramics have been studied in order to investigate the influence of porosity on their functional properties. The BST ceramics with various porosity levels have been obtained by solid-state reaction. Lamellar graphite in different concentration of 10, 20 and 35 vol.%was added as sacrificial pore forming agent. The structural, microstructural, dielectric and tunability properties were investigated. By comparison with dense BST ceramic, porous samples present a fracture mode transformation from intragranular to an intergranular fracture and a decrease of grain size. Lower dielectric constants, low dielectric losses, but higher values of tunability than in the dense material were obtained in the porous BST structures as a result of local field inhomogeneity generated by the presence of air pores-ceramic interfaces.
M. Airimioaei, R. Stanculescu, V. Preutu, C. Ciomaga, N. Horchidan, S. Tascu, D. Lutic, A. Pui, and L. Mitoseriu
Elsevier BV
Roxana E. Stanculescu, Cristina E. Ciomaga, Nadejda Horchidan, Carmen Galassi, Florin Mihai Tufescu, and Liliana Mitoseriu
Elsevier BV
Roxana Stanculescu, Cristina E. Ciomaga, Leontin Padurariu, Pietro Galizia, Nadejda Horchidan, Claudio Capiani, Carmen Galassi, and Liliana Mitoseriu
Elsevier BV
C. S. Olariu, L. Padurariu, R. Stanculescu, C. Baldisserri, C. Galassi, and L. Mitoseriu
AIP Publishing
Anisotropic porous Pb(Zr,Ti)O3 ceramics with various porosity degrees have been studied in order to determine the role of the pore shape and orientation on the low-field dielectric properties. Ceramic samples with formula Pb(Zr0.52Ti0.48)0.976Nb0.024O3 with different porosity degrees (dense, 10%, 20%, 40% vol.) have been prepared by solid state reaction. Taking into consideration the shape and orientation of the pore inclusions, the dielectric properties of porous ceramics have been described by using adapted mixing rules models. Rigorous bounds, derived on the basis on Variational Principle, were used to frame dielectric properties of porous composites. The finite element method (FEM) was additionally used to simulate the dielectric response of the porous composites under various applied fields. Among the few effective medium approximation models adapted for anisotropic oriented inclusions, the best results were obtained in case of needle-like shape inclusions (which do not correspond to the real shape of microstructure inclusions). The general case of Wiener bounds limited well the dielectric properties of anisotropic porous composites in case of parallel orientation. Among the theoretical approaches, FEM technique allowed to simulate the distribution of potential and electric field inside composites and provided a very good agreement between the computed permittivity values and experimental ones.
Luminita Stroia, Roxana-Elena Stanculescu, and Dana Ortansa Dorohoi
SPIE
Two spectrally active molecules - carbanion monosubstituted cycloimmonium ylids having as heterocycles benzo-[f]- quinolinium and p-phenyl-pyridazinium - can offer information about the local field of forces in binary solutions. Hyper Chem. 8.0.6 software was used to characterize these molecules from the structural, energetic and electro-optical point of view. The visible band of the cycloimmonium ylids appears by an intramolecular charge transfer (ICT) from the carbanion to the heterocycle. It is very sensitive to the solvent nature. The projection of the excited state dipole moment on the dipole moment in the electronic ground state was obtained for two studied ylids on the basis of the existent theories regarding the intermolecular interactions in liquid phase studied by spectral means.