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1

Numerical prediction of thermal performance of an electrocaloric device based on ceramic material

Kehileche Brahim, Chiba Younes, Tlemcani Abdelhalim, Henini Noureddine

Przegląd Elektrotechniczny

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2020

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R. 96, nr 9

38--42

EN

The main objective of this work is to efficiency prediction and parameter optimisation of an electrocaloric refrigeration system based on ceramic materials (BaTiO3) and nanofluids (Al2O3, CuO). For this purpose, an electrocaloric device is used and studied. The principle consists in the heating and cooling of the ceramic material under the application and removal of electrical field respectively. The nanoparticles suspended in water increase the heat thermal between solid electrocaloric material and carried fluid, so we have much faster heat exchanges that cause an increase in coefficient of performance (COP) and temperature span; the temperature difference between the cold heat exchanger (CHEX) and the hot heat exchanger (HHEX). Indeed, the performances of these systems are strongly dependent on the interactions between the thermal, the fluidic and the electricity in order to be able to evaluate and optimize these systems in terms of cooling power, and the observation is that there are very few current studies in this area. Finally, a parametric study effected by using the COMSOL Multiphysics identified the characteristic quantities that have a significant influence on thermal behavior in electrocaloric refrigeration systems based nanofluids and ceramic material.

PL

Tematem artykułu jest analiza i optymalizacja systemu chłodzenia bazującego na materiale ceramicznym BaTiO3 i nanocieczy Al2O3, CuO. W tym celu analizowano element elektrokaloryczny I współczynnik wymiany ciepła CCP. Przedstawiono wyniki badań elementu jak I całego systemu chłodzenia.

2

The Application of the Mechanochemical Synthesis for the Preparation of Advanced Ceramics Based on Barium Titanate

Garbarz-Glos B., Bąk W., Budziak A., Dulian P., Lisińska-Czekaj A., Czekaj D.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1391--1396

EN

In the present study, the lead-free BaTi1-x Zrx O3 (for x = 0, 0.05 and 0.15) ceramics were prepared by High-Energy Ball Milling and heat treatments. The performed X-ray, SEM and EDS measurements confirmed high purity, good quality and the expected quantitative composition of the obtained samples. The study of dielectric properties was performed by means of broadband dielectric spectroscopy at the frequency ranging from 0.1 Hz to 10 MHz. The obtained measurement data, analyzed in accordance with the Arrhenius formalism demonstrated the presence of relaxation type dielectric mechanisms. The impedance answer of studied ceramic materials indicated the presence of two relaxation processes: one with a dominant resistive component and the other with a small capacitive component. The observed dielectric relaxation process is temperature dependent and has a “non-Debye” character.

3

Preparatyka nanoproszków tytanianu baru metodą hydrotermalną

Wajler A., Sidorowicz A., Jach K., Węglarz H., Romaniec M., Diduszko R.

Materiały Ceramiczne

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2016

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T. 68, nr 2

105--109

PL

W pracy badano wpływ warunków syntezy hydrotermalnej nanocząstek BaTiO3 z użyciem azotanu, chlorku lub wodorotlenku baru oraz nanoproszku tlenku tytanu w temperaturach 100-200 °C. We wszystkich badanych przypadkach rentgenowska analiza fazowa potwierdziła istnienie BaTiO3. Jednakże, morfologia proszków uzyskiwanych w odmiennych warunkach zasadniczo się różniła. W przypadku zastosowania niższych temperatur syntezy (100-150 °C) cząstki miały postać wielościanów lub kształt gwiazd. Synteza w 200 °C pozwoliła na uzyskanie sferycznych cząstek, których rozmiar i stopień aglomeracji zależały od czasu procesu oraz rodzaju zastosowanych substratów.

EN

In this work the experimental conditions for growth of BaTiO3 nanoparticles in aqueous solutions using of barium nitrate, chloride or hydroxide were studied at 100-200°C. In all of the studied cases XRD proved the existence of BaTiO3 after hydrothermal synthesis. However, the morphology of the obtained powders was different. At lower temperatures (100-150 °C) star-like or polyhedron nanoparticles were observed. Synthesis at 200 °C allowed obtaining spherical particles of size and degree of agglomeration dependent on the process time and the type of the substrates used.

4

Colossal dielectric constant of NaNbO3 doped BaTiO3 ceramics

Cao W. Q., Xu L. F., Ismail M. M., Huang L. L.

Materials Science Poland

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2016

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Vol. 34, No. 2

322--329

EN

BaTiO3 ceramics doped with 0.40 mol% NaNbO3 were prepared using a traditional approach by sintering at temperature of 1250 ºC to 1290 ºC. The prepared ceramics was characterized by very good dielectric properties, such as high dielectric constant (1.5 × 105), low dielectric loss (0.1), and good dielectric temperature stability in the −40 ºC to 100 ºC range for the sample sintered below 1270 ºC. The dielectric characteristics obtained with XPS confirmed that Ti4+ ions remain in the state without any change. The huge increase in dielectric constant in NaNbO3 doped BaTiO3 samples occurs when large amount of Ba2+ ions are excited to a high energy bound state of Ba2+ − e or Ba+ to create electron hopping conduction. For samples with the content of NaNbO3 higher than 0.40 mol%, or sintering temperature higher than 1280 ºC, compensation effect is dominated by cation vacancies with sharply decreasing dielectric constant and increased dielectric loss. The polaron effect is used to explain the relevant mechanism of giant dielectric constant appearing in the ferroelectric phase.

5

Structural and electrical properties of barium titanate (BaTiO3) thin films obtained by spray pyrolysis method

Kumbhar S. S., Mahadik M. A., Chougule P. K., Mohite V. S., Hunge Y. M., Rajpure K. Y., Moholkar A. V., Bhosale C. H.

Materials Science Poland

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2015

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Vol. 33, No. 4

852--861

EN

Barium titanate (BaTiO3) thin films have been prepared using the spray pyrolysis method. The films were deposited onto a glass substrate at varying substrate temperature ranging from 250 to 350 degrees C with the interval of 50 degrees C. The structural, morphological, electrical and dielectric properties of the deposited films have been studied. The X-ray diffraction pattern confirmed the polycrystalline nature of the films with a cubic crystal structure. X-ray photoelectron spectroscopy (XPS) showed a good agreement of the thin films stoichiometry with (BaTiO3). A presence of Ba, Ti and O in the BaTiO3 thin films was observed by energy dispersive X-ray analysis. The scanning electron microscopy (SEM) showed the heterogeneous distribution of cubical grains all over the substrate. The grain size decreased with an increase in substrate temperature. The dielectric constant and dielectric loss showed the dispersion behaviour as a function of frequency, measured in the frequency range of 20 Hz to 1 MHz. The AC conductivity (sigma(ac)) measurement showed the linear nature of obtained films, which confirms conduction mechanism due to small polarons. Impedance spectroscopy has been used to study the electrical behaviour of BaTiO3 ferroelectric thin films. The ferroelectric hysteresis loop has been recorded at room temperature.

6

Fabrication of 0.95BaTiO3-0.05Pb(Mg1/3Nb2/3)O3 ceramics by conventional solid state reaction method

Nogas-Ćwikiel E., Suchanicz J.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 4

1397--1399

EN

The possibility to obtain of ceramic solid solution between barium titanate and lead magnesium niobate by two-step sintering technique through conventional solid-state reaction method has been investigated. In the first step MgNb2O6 has been synthesized. In the second step 0.95BaTiO3-0.05Pb(Mg1/3Nb2/3)O3 has been obtained using MgNb2O6, PbO and BaTiO3. The two-step sintering technique is effective for the synthesized of 0.95BaTiO3-0.05Pb(Mg1/3Nb2/3)O3 ceramics. Single-phase (pyrochlore-free) ceramics with perovskite phase were obtained.

PL

Badano możliwość otrzymania ceramicznego roztworu stałego ty tanianu baru i niobianu ołowiu magnezu metodą reakcji w fazie stałej. Ceramikę otrzymano dwuetapowo. W pierwszym etapie zsyntezowano MgNb2O6. W drugim etapie z 0.95BaTiO3-0.05Pb(Mg1/3Nb2/3)O3 otrzymano 0.95BaTiO3-0.05Pb(Mg1/3Nb2/3)O3. Użyta metoda dwuetapowa okazała się skuteczna dla otrzymania ceramiki 0.95BaTiO3-0.05Pb(Mg1/3Nb2/3)O3. Otrzymano jednofazową ceramikę o strukturze typu perowskitu. bez niepożądanej fazy pirochloru.

7

Synthesis of 0.7BiFeO3-0.3BaTiO3 ceramics: thermal, structural and AC impedance studies

Wodecka-Duś B., Czekaj D.

Archives of Metallurgy and Materials

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2011

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Vol. 56, iss. 4

1127-1136

EN

In a present paper results of the process of synthesis and study of a perovskite-type solid solution of the chemical composition (1-x)BiFeO3-xBaTiO3 for x=0.3 are reported. Synthesis of 0.7BiFeO3-0.3BaTiO3 (BF-BT) ceramics was carried out according to the solid-phase reaction from the mixture of powders. Simultaneous thermal analysis (STA) and X-ray diffraction method were utilized to study the synthesis of BF-BT ceramics. On the basis of STA analysis the optimum conditions of the thermal treatment were found. BF-BT ceramics was studied in terms of its microstructure (SEM), chemical composition (EDS), crystalline structure (XRD), and dielectric properties (impedance spectroscopy) at room temperature. It was found that dense BF-BT ceramics with a cubic structure of Pm3m space group and desired stoichiometry (š3%) was fabricated under technological conditions differing in both sintering temperature (T=750°C-850°C) and soaking time (t=2h-40h). It was found that an increase in sintering temperature for ?T=100°C made it possible to decrease the soaking time 10 times. Impedance spectroscopy was utilized for characterizing dynamical dielectric properties of 0.7BF-0.3BT ceramics. The alternative representation of impedance data in a form of complex plot (Z" vs. Z') as well as simultaneous Bode plots (imaginary parts of impedance Z", admittance Y", electric modulus M" and tan versus frequency in a log-log scale) were used for preliminary visual analysis. Kramers-Kronig transform test was utilized for experimental data validation. To analyze the room temperature impedance spectroscopy data complex nonlinear least squares fitting method was used and the data were fitted to the corresponding equivalent circuit consisting of resistors and constant phase elements. Agreement between experimental and simulated data was established.

PL

W niniejszej pracy przedstawiono rezultaty badań poświęconych wytwarzaniu i charakterystyce właściwosci roztworu stałego o strukturze typu perowskitu i składzie chemicznym (1-x)BiFeO3–xBaTiO3 dla x=0,3. Proces syntezy ceramiki 0,7BiFeO3–0,3BaTiO3 (BF-BT) przeprowadzono w wyniku reakcji w fazie stałej z mieszaniny prostych tlenków. Przy pomocy analizy termicznej (STA) oraz rentgenowskiej analizy strukturalnej dokonano charakterystyki procesu syntezy ceramiki BF-BT. Przeprowadzono badania mikrostruktury ceramiki BF-BT za pomoca skaningowego mikroskopu elektronowego (SEM), określono stechiometrie składu chemicznego przy użyciu metody EDS, a strukture krystaliczna badano metoda dyfrakcji rentgenowskiej (RTG). Przeprowadzono badania właściwosci dielektyrcznych wytworzonej ceramiki metodą spektroskopii impedancyjnej. Wykorzystując metodę swobodnego spiekania dla trzech różnych warunków technologicznych (T=750-880 C, t=2-40h) otrzymano ceramike 0,7BF–0,3BT o dużej czystości i homogenicznosci składu (3%), wykazujaca strukture regularna Pm3m. Na podstawie przeprowadzonych badań stwierdzono, iż zwiększenie temperatury syntezy i spiekania o T=100 C, pozwoliło zmniejszyć czas wytrzymania ceramiki 10 razy. Badania przeprowadzone metoda spektroskopii impedancyjnej pozwoliły na scharakteryzowanie właściwosci dielektrycznych ceramiki 0,7BF–0,3BT. Dane impedancyjne przedstawiono w płaszczyznie zespolonej Z" od Z' oraz w postaci zależności częstotliwościowych urojonych składowych impedancji Z"(v), modułu elektrycznego M"0(v), admitancji Y"(v) i strat dielektrycznych tg(v). Spójność danych pomiarowych sprawdzono przy pomocy metodyki Kramersa-Kroniga, która potwierdziła poprawność danych eksperymentalnych.

8

The influence of barium titanate as a filler in impregnating epoxy resin on chosen electrical parameters of obtained material

Kasprzak W., Nadolny Z., Walczak K., Siodła K., Sikorski W., Jóźwiak K., Paściak G., Moroń L.

Materials Science Poland

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2009

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Vol. 27, No. 4/2

1219--1227

EN

The paper describes the influence of barium titanate BaTiO3 used as a filler in impregnating epoxy resin on electrical parameters of obtained material. The results of computer simulation of electric field intensity distribution in area of 220 kV ac composite insulator show that in order to reduce the maximum value of this field it is necessary to use the rod with the highest possible permittivity. It was assumed that the increase of rod permittivity is possible by doping the epoxy resin, being one of glass-epoxy rod components, with a filler having high permittivity. Barium titanate BaTiO3 in micro- and nanograins was used as a filler. Presumably, such a change in material structure, may negatively influence other electrical parameters of the material, important in composite insulators construction. In order to check the filler dispersion in epoxy matrix, microscopic observations of fractions of the obtained materials were performed. In a wide range of frequencies, the permittivity and volume resistivity of the materials were determined. The inception voltage of partial discharges on surface of materials was determined by the electric, acoustic and antenna methods.

9

Analysis of quadratic electrooptic response of BaTiO₃ crystal in ferroelectric phase

Izdebski M., Kucharczyk W.

Opto-Electronics Review

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2008

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Vol. 16, No. 1

42-45

EN

Using the example of BaTiO₃ in a ferroelectric phase it is shown that a large difference in magnitudes of individual linear electrooptic coefficients may be a reason of additional indirect quadratic contributions that are independent of real quadratic coefficients. For some directions of the applied field and light, the indirect contributions may be even larger than the real quadratic ones. Independently of nonlinear distortions that can affect applicability of technical devices, a large difference between linear electrooptic coefficients may lead to serious problems in measurements of the real quadratic electrooptic effect. The analysis is based on the extended Jones matrix calculus applied to a Gaussian beam.

10

Electronic properties of thin niobium doped barium titanate films

Firek P., Ćwil M., Werbowy A., Szmidt J.

Materiały Elektroniczne

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2008

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T. 36, nr 3

110-116

EN

This work presents results of investigations of barium titanate thin films with Nb2O5 admixture, deposited on Si substrates by means of Radio Frequency Plasma Sputtering (RF PS) of sintered BaTiO3 + Nb2O5 target. Round, aluminum (Al) electrodes were evaporated on the top of deposited layers. Thus, metal-insulator-semiconductor (MIS) structures were created with BaTiO3 thin films playing the role of the insulator. They enabled subsequent electrical characterization (current-voltage (I-V) and capacitance-voltage (C-V) measurements) of studied material. This allowed extraction of several electronic parameters (e.g. εn, ρ, VFB ΔVH). Films composition were additionally studied using secondary ion mass spectroscopy (SIMS) techniques.

PL

W pracy prezentowane są wyniki badań dotyczące cienkich warstw tytanianu baru (BaTiO3) z domieszką Nb2O5. Powłoki zostały osadzone metodą rozpylania targetu w plazmie o częstotliwości radiowej (Radio Freąuency Plasma Sputtering - RF PS), a następnie poprzez próżniowe naparowanie elektrod aluminiowych na powierzchnie BaTiO3, zostały wytworzone struktury metal-dielektryk-półprzewodnik (MIS). Pozwoliło to na charakteryzacje elektryczną (pomiary prądowo-napięciowe (I-V) i pojemnościowo-napięciowe (C-V)) kondensatorów, gdzie warstwa tytanianu baru występowała jako dielektryk. Wyznaczone zostały parametry takie jak: εn, ρ, VFB, ΔVH, . Ponadto zmierzono profil warstwy przy użyciu spektroskopii mas jonów wtórnych (secondary ion mass spectroscopy - SIMS).

11

The influence of barium titanate bati03 as a filler in impregnating epoxy resin on chosen electrical parameters of obtained material.

Kasprzak W., Nadolny Z., Walczak K., Siodła K., Sikorski W., Józwiak K., Paścik G., Moron L.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

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2007

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Vol. 46, nr 19

165-170

EN

The paper describes the influence of barium titanate BaTiO3 used as a filler in impregnating epoxy resin on electrical parameters of obtained material. The results of computer simulation of electric filed intensity distribution in area of 220 kV AC composite insulator show, that in order to reduce the maximal value of this field it is necessary to use the rod with the highest possible permittivity. It was assumed that the increase of rod permittivity is possible by doping the epoxy resin, being one of glass-epoxy rod components, with a filler having high permittivity value. Barium titanate BaTi03 in micro- and nanograms was chosen as the filler. Presumably, such a change in material structure, may negatively influence other electrical parameters of obtained material, important in composite insulators construction. In order to check the filler dispersion in epoxy matrix, microscopical observations of obtained materials fractions were performed. In wide range of frequency, the permittivity and volume resistivity of obtained materials in were determined. The inception voltage of partial discharges on surface of materials was determined with electric, acoustic and antenna methods.