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1

Frequency and temperature dependence of dielectric and electric properties of Ba2-xSm4+2x/3Ti8O24 with structural analysis

Narang S. B., Kaur D., Pubby K.

Materials Science Poland

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2015

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Vol. 33, No. 2

268--277

EN

Dielectric ceramics samples of barium titanium oxide doped with samarium, having a complex structural formula of Ba2-xSm4+2x/3Ti8O24 (referred to as BST), were fabricated by a high temperature solid-state reaction technique with varying x (0.0, 0.2, 0.4, 0.6). X-ray diffraction technique was used to check the formation of particular phases. Scanning electron microscope technique was used to study the surface morphology of the samples. The samples were studied in a temperature range of 298 K to 623 K and frequency range of 10 KHz to 1 MHz. The dielectric constant (εr), loss tangent (tanδ), and AC conductivity (σAC) were measured on sintered disks of BST samples. The DC resistivity of different compositions was measured at room temperature. Detailed studies of dielectric and electrical properties showed that these properties are strongly dependent on composition, frequency and temperature. The compounds showed stable behavior in lower temperature range (up to 523 K), therefore, they can be used in practical applications in this temperature range.

2

Measurement of Electrical Properties as Effectiveness Appraisal of Microwave Absorption by Moulding and Core Sands Subject to Microwave Utilization

Nowak D., Granat K., Opyd B

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 2

713--716

EN

Within the research, carried-out were examinations of foundry rejects in form of waste moulding and core sands in order to determine effectiveness of the microwave utilization process. Presented are measurements of permittivity and loss tangent that determine behaviour of materials in electromagnetic field. Measurements were performed on a stand of waveguide resonance cavity that permits precise determination of the above-mentioned parameters with the perturbation method. Examination results of five waste moulding sands confirm that effectiveness of microwave utilization depends on electrical properties of the sandmixes (permittivity and loss tangent).

PL

W pracy podjęto badania odpadów odlewniczych w postaci zużytych mas formierskich i rdzeniowych w celu określenia skuteczności procesu mikrofalowej utylizacji. Przedstawiono wyniki pomiarów przenikałności elektrycznej oraz tangensa kąta stratności. które określają zachowanie materiałów w polu elektromagnetycznym. Pomiary przeprowadzono na stanowisku falowodowej wnęki rezonansowej, która umożliwia precyzyjne wyznaczenie metodą perturbacyjną wymienionych parametrów. Badania pięciu zużytych mas formierskich i rdzeniowych potwierdzają, iż skuteczność mikrofalowej utylizacji jest zależna od ich właściwości elektrycznych (przenikalności elektrycznej oraz tangensa kąta stratności).

3

Theoretical study of ferroelectric triglycine sulphate (TGS) crystal in external electric fields

Upadhyay T. Ch., Nautiyal A.

International Letters of Chemistry, Physics and Astronomy

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2013

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Vol. 6

54-65

EN

A modified two sub-lattice pseudospin-lattice coupled mode model of Mitsui et al [Phys. Rev., 111 (1958) 1259] by adding third, fourth order phonon anharmonic interaction and external electric field terms has been applied to ferroelectric triglycine sulphate crystal. Electric field dependence of ferroelectric, dielectric and acoustical properties has been studied. With the help of double time temperature dependent Green’s function method, expressions for shift, width, soft mode frequency, dielectric constant, loss tangent and acoustic attenuation have been derived. Numerically calculations have been made and results have been compared with experimental data reported by Bye et al [Ferroelectrics 4 (1974) 243] and Shreekumar et al [Ferroelectrics 160 (1994) 23] for TGS crystal and a good agreement has been observed.

4

Usefulness of foundry tooling materials in microwave heating process

Granat K., Opyd B, Nowak D., Stachowicz M., Jaworski G.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 3

919--922

EN

The paper describes preliminary examinations on establishing usefulness criteria of foundry tooling materials in the microwave heating technology. Presented are measurement results of permittivity and loss tangent that determine behaviour of the materials in electromagnetic field. The measurements were carried-out in a waveguide resonant cavity that permits precise determination the above-mentioned parameters by perturbation technique. Examined were five different materials designed for use in foundry tooling. Determined was the loss factor that permits evaluating usefulness of materials in microwave heating technology. It was demonstrated that the selected plastics meet the basic criterion that is transparency for electromagnetic radiation.

PL

W pracy podjęto wstępne badania nad ustaleniem kryteriów oceny przydatności materiałów do budowy oprzyrządowania odlewniczego, przewidzianego do zastosowania w technologii nagrzewania mikrofalowego. Przedstawiono wyniki pomiarów przenikalności elektrycznej oraz tangensa kąta stratności, które określają zachowanie materiałów w polu elektromagnetycznym. Pomiary przeprowadzono na stanowisku falowodowej wnęki rezonansowej, która umożliwia precyzyjne wyznaczenie metodą perturbacyjną wymienionych parametrów. Badaniom poddano piec różnych materiałów przewidzianych do zastosowania w budowie oprzyrządowania odlewniczego. Określono współczynnik stratności, który pozwala, na ocenę przydatności materiałów w technologii nagrzewania mikrofalowego. Wykazano, że wybrane tworzywa sztuczne spełniają podstawowe kryterium, jakim jest transparentność dla promieniowania elektromagnetycznego.

5

Określenie możliwości zastosowania w procesach nagrzewania mikrofalowego oprzyrządowania odlewniczego z drewna

Granat K., Opyd B., Nowak D., Stachowicz M.

Archives of Foundry Engineering

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2013

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Vol. 13, iss. 1 spec.

135--138

PL

W pracy przedstawiono wyniki badań wstępnych nad możliwością zastosowania różnych gatunków drewna do budowy oprzyrządowania odlewniczego, przewidzianego przy procesie nagrzewania mikrofalowego mas formierskich i rdzeniowych. Badania podjęto w celu oceny tych materiałów z punktu widzenia kryterium transparentności dla promieniowania mikrofalowego. Pomiary przeprowadzono metodą perturbacyjną na stanowisku falowodowej wnęki rezonansowej, która umożliwia precyzyjne wyznaczenie tangensa kąta stratności oraz przenikalności dielektrycznej materiałów konstrukcyjnych. Wykazano, iż wszystkie wybrane gatunki drewna charakteryzują się zbliżonym współczynnikiem stratności, który determinuje możliwości ich zastosowania do budowy oprzyrządowania odlewniczego, przewidywanego do pracy w polu elektromagnetycznym.

EN

The paper presents the results of preliminary studies on the possibility of using different types of wood to construct foundry tooling, designed for microwave heating process of moulding and core sands. The study was undertaken to evaluate these materials from viewpoint of transparency criterion for microwave radiation. The measurements were carried out in a waveguide resonant cavity that permits precise determination permittivity and loss tangent by perturbation technique. It was demonstrated that all of the selected wood species are characterized by a similar loss factor that determines the possibility of their use in the construction of foundry tooling, intended for use in the electromagnetic field.

6

Electric properties of ice near solidification and melting temperature

Rusiniak L.

Acta Geophysica Polonica

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2004

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Vol. 52, nr 3

363-380

EN

The dielectric permittivity, conductivity and loss tangent of ice were measured for different thicknesses of the sample (0.1-4 mm). In this investigation, the measurement of thin samples can be treated as a laboratory test of surface proper-ties and that of thick samples as a test of bulk properties. The measurements were carried out from 3.5 to -13.5°C with descending and growing temperature. Two domain Debye resonances were observed. The one at low frequency is interpreted as being associated with transversal mode, and the other, at higher frequency, is associated with longitudinal mode of proton domain. The resonance frequencies depend on sample size and temperature. Temperature hysteresis of resonance frequencies was observed. As the temperature grows starting from low temperature, the resonance frequencies move towards each other and finally the two modes join to form one mode. The dielectric constant associated with transversal mode is higher than 104. The dielectric constant associated with longitudinal mode is about 102. The dipole dielectric constant vanishes after solidification. As the temperature grows, the di-pole dielectric constant grows too. Oscillation of dielectric permittivity and conductance for a small value of oscillator level was observed. The experimental data show that ice could be both a ferroelectric and a piezoelectric material.

7

Whispering gallery resonator method for permittivity measurements

Derzakowski K., Abramowicz A., Krupka J.

Journal of Telecommunications and Information Technology

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2002

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nr 1

43-47

EN

The new method of measuring permittivity is described. The measurements are performed using whispering gallery mode open dielectric resonators. The accuracy is assured by applications of the mode matching method. Three resonant modes (HE511, HE611 and HE711) are used in measurement procedure. Accuracy of the method is much better than 0.3% for the relative permittivity having values from 20 to 50.