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- ItemOptical and electrical performance of translucent BaTiO3-BaSnO3 ceramics(ELSEVIER SCI LTD, 2024-08-15) Bijalwan, Vijay; Kaštyl, Jaroslav; Erhart, Jiří; Prajzler, Vladimír; Tofel, Pavel; Sobola, Dinara; Velazquez, Jose J.; Galusek, Dušan; Maca, KarelLead-free piezoceramic with the composition of 0.89BaTiO(3)-0.11BaSnO(3) (BT-11BS) was prepared by solid-state reaction followed by conventional sintering achieving nearly full density. The influence of sintering temperature on electrical properties were thoroughly investigated, implying a significant role in achieving best properties, which were obtained between 1420 and 1440 degrees C. The addition of SnO2 in BaTiO3 solid solution promoted grain growth, eventually resulting in the grain sizes between 145 and 216 mu m. An ultra-high dielectric permittivity >5.0 x 10(4) and related dielectric loss of 3.1 % at similar to 40 degrees C was achieved. A high value of quasi-static piezoelectric constant (d(33)) of 693 pC/N and the converse piezoelectric constant (denoted as d(33)*) reached a value of up to 831 pm/V in the frequency range between 10 and 110 Hz. The transmittance of similar to 25 % in the visible region and similar to 40 % in the infrared region together with good electromechanical properties showcasing a unique combination for this material.
- ItemBasic microstructural, mechanical, electrical and optical characterisation of BaTiAl6O12 ceramics(Elsevier, 2024-06-27) Drdlík, Daniel; Mařák, Vojtěch; Klement, Róbert; Tofel, Pavel; Drdlíková, Katarina; Hadraba, Hynek; Chlup, ZdeněkIn progressive particle or layered composites based on a combination of BaTiO3 and Al2O3, serving as e.g. ceramic harvesters, new phases are formed during heat treatment. The dominant one is BaTiAl6O12. This study provides information about the microstructural, mechanical and optical properties of the BaTiAl6O12 ceramics. The evolution of the phases during the solid-state reaction synthesis of the BaTiAl6O12 was monitored. The fully dense samples prepared by Spark Plasma Sintering had indentation Vickers hardness and indentation elastic modulus within ranges of 10.1 – 13.7 GPa and 132.0 – 187.0 GPa, depending on loading force. The three-point bending tests of the BaTiAl6O12 samples resulted in flexural strength of 129.9 MPa and fracture toughness of 1.8 MPa.m1/2.The sample showed blue broad-band emission under UV excitation due to the charge-transfer transition of the Ti4+ and defect sites. The BaTiAl6O12 evinced low permittivity (') = 16 and dielectric loss (tan ) < 0.0003 at a frequency 1 kHz.
- ItemComprehensive analysis of charge carriers dynamics through the honeycomb structure of graphite thin films and polymer graphite with applications in cold field emission and scanning tunneling microscopy(ELSEVIER, 2024-09-13) Allaham, Mohammad Mahmoud; Daradkeh, Samer; Al-Braikat, Hatem; Dallaev, Rashid; Burda, Daniel; Košelová, Zuzana; Al-Akhras, M-Ali; Jaber, Ahmad; Mousa, Marwan; Sobola, Dinara; Kolařík, Vladimír; Knápek, AlexandrPolymer graphite electron sources have performed satisfactorily as field emission emitters and scanning tunneling microscopy probes in the past few years. However, the emission process was characterized by limited total emission currents. This paper introduces the elemental, vibrational, electronic structure, and optical analysis of polymer graphite and glass-graphite composite field emission cathodes to study these limitations. Moreover, the field emission characteristics are studied including the changes in the potential energy barrier of the used materials and structures. Among the studied structures, the cathodes prepared from graphite thin films deposited on a micropointed glass substrate (film-GMF) showed superior performance as random field emission arrays. This includes obtaining much higher emission current values 20 times) and lower threshold voltages 1/2) compared to the results obtained from polymer graphite samples. The enhancement factor in such emitters is believed to be the three-dimensional honeycomb structure of graphite. Moreover, the study includes applying graphite coatings to tungsten nano-field emission cathodes and scanning tunneling microscopy probes, which improves the performance of such cathodes/probes in both microscopic techniques.
- ItemOptical Properties of YttriumOrthoferrite Films Prepared by PlasmaLaser Deposition(Preprints.org, 2024-08-08) Sobola, Dinara; Fawaeer, Saleh Hekmat Saleh; Kočková, Pavla; Schubert, Richard; Dallaev, Rashid; Trčka, TomášThis study investigates the optical properties of Yttrium Orthoferrite thin films fabricated via plasma laser deposition. Yttrium Orthoferrite, a ferrimagnetic material known for its potential applications in spintronics and photonics, was deposited on single-crystal substrates under controlled conditions to analyze its optical characteristics. The influence of deposition time, on the film quality and optical properties was examined.
- ItemComprehensive Analysis of E478 Single-Component Epoxy Resin and Tungsten-E478 Interface for Metallic-Polymer Composite Electron Source Applications(American Chemical Society, 2024-06-29) Allaham, Mohammad MahmoudThis study provides comprehensive elemental, optical, and energy gap characteristics of the E478 single-component epoxy resin. This type of epoxy resin has imperative applications in medium voltage insulation and cold field emission of electrons. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and hydrogen nuclear magnetic resonance (1H-NMR) were used to study the elemental and structural analyses, ultraviolet photoelectron spectroscopy (UPS) was used to obtain the local work function and the ionization potential energies, and ultraviolet/visible light spectroscopy (UV/VIS) was used to report the optical and energy gap characteristics of the epoxy resin being studied. Moreover, the UPS and UV/VIS analyses were merged to obtain the electron affinity of the E478 epoxy resin and to study the epoxy's energy band diagram and the tungsten-epoxy interface band structure. The results showed that the E478 epoxy resin is considered an n-type semiconductor of energy gap similar to 3.94 eV, local work function similar to 3.42 eV, ionization potential similar to 6.10 eV, electron affinity similar to 2.16 eV, and tungsten-epoxy Schottky contact barrier height similar to 2.50 eV.