Search results

1

Effects of B₂O₃ Addition on the Sintering Behavior of 0-5-10% ZrO₂ Doped BaTiO₃ Based Ceramics

100%

Öksüz K., Şen Ş., Şen U.

Acta Physica Polonica A

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2015

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vol. 127

|

issue 4

1086-1089

EN

In this study, the effect of B₂O₃ addition on the sintering behavior of 0-5-10% ZrO₂ doped barium titanate based microwave dielectric ceramics were investigated. For this purpose, the powder mixtures consisting of BaCO₃, TiO₂ and ZrO₂ were prepared by ball milling technique in alcohol using ZrO₂ balls at 200 cycle/min for 20 h. The prepared powders were calcined at 900°C for 2 h. Produced powders were mixed 0.5% B₂O₃ and 5% PVA and pressed as green body under the pressure of 100 MPa. The disc-shaped die-pressed samples were sintered at 1250°C, 1350°C and 1450°C for 4 h. X-ray diffraction analysis showed that the main phases formed in the sintered samples are BaTiO₃ and Ba(Ti_{1-x}Zr_{x})O₃. The scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to investigate microstructure of the sintered samples. The bulk densities of the sintered samples increased with the addition of B₂O₃ content due to the low number of pores trapped between the grains.

2

^1H NMR Study of Molecular Dynamics of 4-apyH Cation under High Hydrostatic Pressure

100%

Medycki W., Świergiel J., Jakubas R., Hołderna-Natkaniec K.

Acta Physica Polonica A

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2005

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vol. 108

|

issue 1

161-164

EN

Polycrystalline [4-NH_2C_5H_4NH] SbCl_4 and [4-NH_2C_5H_4NH] SbCl_6 have been investigated by proton NMR methods between 120 K and 370 K under hydrostatic pressure of 0.1 and 520 MPa. Reduction in the dipolar second moment is interpreted in terms of cation reorientation. Activation energies characterizing the motion increase with increasing pressure.

3

Peculiarities of Dielectric Relaxation in DMAAS Ferroelectric Crystals

100%

Kapustianik V., Czapla Z., Czukwinski R.

Acta Physica Polonica A

|

2002

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vol. 102

|

issue 3

365-372

EN

This paper presents the results of investigations of the dielectric properties of NH_2(CH_3)_2Al(SO_4)_2×6H_2O crystals performed in a wide frequency range. In particular, the temperature and frequency dependences of the dielectric permittivity were measured in the region of ferroelectric phase at different rates of temperature change. The thermal dipole relaxation with a critical slowing-down at T_{c1} was observed at comparatively low frequencies of measuring field. The relaxation connected with the domain freezing takes place at still lower frequencies (below 100 kHz) and was found to be strongly dependent on the rate of the temperature change. It was shown that deuteration results in a noticeable change of the parameters characterising this process including the temperature of domain wall freezing.

4

The Pb(Fe_{1/2}Nb_{1/2})O_3 Ferroelectromagnetic Ceramics in a View of Possibilities to be Used for Electric Transducers

80%

Bochenek D., Zachariasz R.

Acta Physica Polonica A

|

2008

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vol. 114

|

issue 6A

A-15-A-20

EN

The PbFe_{1/2}Nb_{1/2}O_3 (PFN) ceramics can be obtained by a lot of ways. There are a lot of methods and techniques to synthesize the PFN powder such as: reactions in the solid phase by one-stage or two-stage synthesizing method (the columbite method), molten salt synthesis, sol-gel, co-precipitation method and sintering of compacts from a loose mixture of powders. Each of them requires accuracy and precision to conduct a technological process, aiming at obtaining a product with the optimum parameters. In the work PFN specimens were obtained by one-stage synthesis methods using two different powder synthesizing techniques: by calcining (sintering of a loose mixture of the PFN powder) and as a result of sintering of pressed compacts from the PFN powder mixture at high temperature (pressing). The obtained specimens were subjected to X-ray and micro-structural examinations and tests of internal friction and dielectric properties. The tests showed that the ceramics obtained by the powder calcining method has better applied properties.

5

Electrical Charge Transfer in Complex Oxides

80%

Shevchuk V., Kayun I.

Acta Physica Polonica A

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2010

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vol. 117

|

issue 1

150-154

EN

The electrophysical properties (temperature-frequency dependence of conductivity and dielectric constant, current of depolarization) of complex oxide single crystals (Ca-Ga-Ge-garnet, Ca-Ga-germanate, Pb-, Ca-, Cd-tungstates) are analyzed. The experimental results for different crystallographic axes were obtained in the frequency range 10-10^{5} Hz and temperature range 290-650 K. The main parameters of conductivity and depolarization currents are determined. The nature of polarization charge induced by applied external field is discussed using the model of polarization at hopping exchange of charge between complex dipolar defects and space-inhomogeneous distribution of charge in the sample. Existence of small polarons in the crystals is considered.

6

Dielectric and Electrooptic Investigations of B Phases οf Banana-Shaped Thioesters

80%

Wierzejska-Adamowicz M., Ossowska-Chruściel D., Chruściel J., Douali R., Legrand C., Marzec M., Mikułko A., Sikorska A., Wróbel S.

Acta Physica Polonica A

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2010

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vol. 117

|

issue 4

557-561

EN

Electrooptic and dielectric measurements were done for B phases of two banana-shaped homologues 1,3-phenylene bis{4-[(4-nonylo-xy-benzoyl)sulfanyl]benzoate (9OSOR) and 1,3-phenylene bis{4-[(4-dodecylo-xy-benzoyl)sulfanyl]benzoate (12OSOR). Polarizing microscopy allowed to identify B_{1} phase for 9OSOR and B_{2} phase for 12OSOR on the basis of texture observation. Spontaneous polarization measurements were performed using reversal current method. The current response to applied triangular voltage shows that B_{1} phase is a ferroelectric and B_{2} phase - antiferroelectric one for which two well separated peaks were observed. Polarization for phase B_{1} of 9OSOR is rather small and its temperature dependence is unusual for ferroelectric liquid crystals - it increases with temperature. Spontaneous polarization for B_{2} phase of 12OSOR compound is of about 600 nC/cm^{2}. Dielectric spectra measured with bias field for B_{2} phase of 12OSOR show two well separated relaxation processes. In the low frequency range the relaxation process is connected with fluctuations of ferroelectric domains. The relaxation process in the high frequency range appearing also without bias field is connected with molecular reorientation. The dielectric spectra measured for B_{1} phase of 9OSOR with and without bias voltage showed only one dielectric relaxation process connected with molecular reorientation around the short axis.

7

Influence of the sample orientation in Sn2P2S6 crystals on the hydrostatic piezoelectric coefficients

80%

Panoŝ S., Panoŝová D.

Open Physics

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2003

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vol. 1

|

issue 1

91-99

EN

The influence of the sample orientation on the effective value of the hydrostatic piezoelectric coefficients dh(i) of Sn2P2S6 crystals has been studied. The hydrostatic piezoelectric coefficients dh(1) and d′h(3), were measured, dh(1)=(244±3) pC/N and d′h(3)=(92±1) pC/N. The hydrostatic piezoelectric coefficient d h(3) for orthogonal axis system was calculated to be dh(3)=(87±2) pC/N. The, optimal orientation of the sample has been found as (Xy l)−20°-cut. Maximal value of the effective hydrostatic piezoelectric coefficient d h(1) equals 260 pC/N. Double rotated samples were also studied. The orientation of the samples insensitive to the pressure has been found. The theoretical mean value of hydrostatic piezoelectric coefficient (d h)mean corresponding to randomly oriented Sn2P2S6 grains in a poled composite has been calculated to be (d h)mean=136 pC/N.

8

The Influence of Partial Isomorphic Substitution on Electronic and Optical Parameters of ABSO₄ Group Crystals

80%

Shchepanskyi P., Gaba V., Stadnyk V., Rudysh M., Brezvin R., Piasecki M.

Acta Physica Polonica A

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2018

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vol. 133

|

issue 4

819-823

EN

First principles calculations of band energy, density of states and dielectric function of K_{1.75}(NH₄)_{0.25}SO₄ single crystals in Pnma structure is performed in the framework of density functional theory. In order to describe the exchange-correlation interaction the general gradient approximation and local density approximation are used. Character and genesis of main energy bands of the crystal are discussed and comparison with data set for K₂SO₄ isomorphic crystal performed. The influence of partial isomorphic substitution K→ NH₄ found itself mainly in altering the bottom of conduction band and decrease of band gap value. From the dielectric functions dependences, the refractive indices dispersion and absorption coefficient spectra are deduced. Obtained refractive indices satisfactorily agree with experimental data in the visible spectrum region.

9

Electronic Structure of BiFeO₃ in Different Crystal Phases

80%

Kaczkowski J., Pugaczowa-Michalska M., Jezierski A.

Acta Physica Polonica A

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2015

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vol. 127

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issue 2

266-268

EN

The electronic structure of different phases of BiFeO₃ were calculated by using density functional theory. The DFT+U and semilocal Tran-Blaha modified Becke-Johnson potential were used. DFT+U results are in good agreement with previous calculations. Our results have shown that in case of R3c, Pnma, Pn2₁a BiFeO₃ has G-antiferromagnetic ordering and C-antiferromagnetic in case of Cm space group. In all calculated structures BiFeO₃ is a semiconductor with the band gap: 2.26 eV (2.27 eV) for R3c, 1.91 eV (1.66 eV) for Pnma, 1.99 eV (2.18 eV) for Pn2₁a and 2.09 eV (2.55 eV) for Cm within DFT+U (Tran-Blaha modified Becke-Johnson).

10

Characterization of Barium Titanate Ceramic Powders by Raman Spectroscopy

80%

Lazarević Z., Romčević N., Vijatović M., Paunović N., Romčević M., Stojanović B., Dohčević-Mitrović Z.

Acta Physica Polonica A

|

2009

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vol. 115

|

issue 4

808-810

EN

Barium titanate, BaTiO_3 ceramic powders were prepared by mechanochemical synthesis and by the Pechini method. A powder mixture of BaO and TiO_2 was treated in a planetary ball mill in an air atmosphere for up to 1 h, using zirconium oxide vial and zirconium oxide balls as the milling medium. After 60 min BaTiO_3 phase was formed. In both ways BaTiO_3 ceramics were sintered after 2 h on 1300°C without pre-calcinations step. The heating rate was 10°C min^{-1}. The formation of phase and crystal structure of BaTiO_3 was approved by X-ray diffraction analysis and the Raman spectroscopy. The morphology and microstructure of obtained powders were examined by scanning electron microscopy method. Sharp phase transition from ferroelectric to paraelectric state was observed. The hysteresis loop is very well performed with regular sharp characteristic of ferroelectric materials.

11

Polarization Induced Effects in AlGaN/GaN Heterostructures

80%

Ambacher O.

Acta Physica Polonica A

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2000

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vol. 98

|

issue 3

195-201

EN

Two-dimensional hole and electron gases in wurtzite GaN/Al_{x}Ga_{1-x}N/GaN heterostructures areinduced by strong polarization induced effects. The sheet carrier concentration and the confinement of the two-dimensional carrier gases located close to one of the AlGaN/GaN interfaces are sensitive to a high number of different physical properties such as polarity, alloy composition, strain, thickness, and doping. We have investigated the structural quality, the carrier concentration profiles, and electrical transport properties by a combination of high resolution X-ray diffraction, Hall effect, and C-V profiling measurements. The investigated heterostructures with N- and Ga-face polarity were grown by metalorganic vapor phase or plasma induced molecular beam epitaxy covering a broad range of alloy compositions and barrier thickness. By comparison of theoretical and experimental results we demonstrate that the formation of two-dimensional hole and electron gases in GaN/AlGaN/GaN heterostructures both rely on the difference of the polarization between the AlGaN and the GaN layer. In addition the role of polarity on the carrier accumulation at different interfaces in n- and p-doped heterostructures will be discussed in detail.

12

Impedance Spectra of As-Grown and Heat Treated Na_{0.5}Bi_{0.5}TiO₃ Crystals

80%

Kruzina T., Sidak V., Trubitsyn M., Popov S., Tuluk A., Suchanicz J.

Acta Physica Polonica A

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2018

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vol. 133

|

issue 4

816-818

EN

The complex impedance spectra Z*(ω) were studied for as-grown and annealed in air Na_{0.5}Bi_{0.5}TiO₃ single crystals. Experimental data showed that annealing significantly increased impedance and led to appearance of low frequency Z* relaxation. The detected relaxation processes were associated with charge transfer within the regions with initial and reduced after annealing concentration of oxygen vacancies.

13

In situ Investigation of OH^{-} Absorption in LiNbO_{3} and LiNbO_{3}:MgO Crystals during Reducing/Oxidizing Annealing

80%

Sugak Y., Sugak D., Zhydachevskii Y., Solskii I., Buryy O., Ubizskii S., Becker K.

Acta Physica Polonica A

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2010

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vol. 117

|

issue 1

170-173

EN

The work presents experimental results of an in situ investigation of the OH^{-} absorption in pure and MgO-doped LiNbO_{3} crystals during reducing (95% Ar + 5% H_{2}) and oxidizing (O_{2}) high-temperature treatments in the temperature range from room temperature to 820 K. The absorption spectra measured in situ at high temperatures in reducing/oxidizing atmospheres have been analyzed. The origin of the changes in optical absorption caused by heating of the crystal is discussed in terms of the OH-bonds orientation change.

14

Vibronic Magnetoelectric Effects in the Bi-Based Multiferroics

80%

Konsin P., Sorkin B.

Acta Physica Polonica A

|

2015

|

vol. 127

|

issue 2

243-244

EN

The detailed magneto-electron-lattice (vibronic) theory of ferroelectricity in the Bi-based multiferroics (BiFeO₃ etc.) is developed further. The vibronic admixture of the empty oxygen 2p states to the Bi 6s lone electron pair state leads to ferroelectricity. These interactions are the driving and restoring forces of the structural phase transformations of the Bi-based multiferroics. The free energy of the BiFeO₃-type multiferroics with the ferroelectric and the G-type antiferromagnetic phase transitions are derived. The Zeeman splitting and spin-transversal optical phonon couplings are also important.

15

Modes Orthogonality of the Mechanical System Simple Supported Beam-Actuators-Concentrated Masses

80%

Brański A.

Acta Physica Polonica A

|

2012

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vol. 121

|

issue 1A

A-126-A-131

EN

This paper deals with simple supported beam-actuators-concentrated masses mechanical system; it appears in active vibration reduction problem. To solve the problem with the Fourier method, the system is discretized into uniform elements. In the paper the orthogonality condition of the modes of the discretized system is derived. Furthermore, the solution of the forced vibration problem of the above system, appearing inherently in the active vibration reduction problem, is outlined.

16

Electrical, Electromechanical and Piezoelectric Properties of Ca₃TaGa₃Si₂O₁₄ Resonators at Elevated Temperatures

80%

Suhak Y., Schulz M., Sotnikov A., Schmidt H., Fritze H.

Acta Physica Polonica A

|

2018

|

vol. 133

|

issue 4

1069-1073

EN

The electrical conductivity, resonance frequency and piezoelectric strain constants are determined for ordered piezoelectric Ca₃TaGa₃Si₂O₁₄ (CTGS) single crystals from room temperature to 900°C. The latter result from three independent methods, namely resonant, ultrasonic pulse-echo, and laser Doppler vibrometry techniques, which allows validating the results. Further, the long-term behaviour of fundamental materials properties including electrical conductivity and resonance frequency are examined at 1000°C for CTGS crystals, grown by different manufacturers. After an initial period of about 500 h, the conductivity is found to remain nearly constant for at least 1500 h. In a period of 2000-5000 h a decrease of conductivity by only 20% is observed. The resonance frequency is found to decrease almost linearly in a period of 500-5000 h for all investigated samples.

17

Influence of ZrO₂ Addition on the Structure and Dielectric Properties of BaTiO₃ Ceramics

80%

Oksuz K., Sen S., Sen U.

Acta Physica Polonica A

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2017

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vol. 131

|

issue 1

197-199

EN

Ba(Ti_{1-x}Zr_{x})O₃ (x=0÷0.3) ceramics were prepared by the standard solid state reaction method and were sintered at 1450°C for 4 h. The structural and dielectric properties of the samples were studied. The phases formed in the ZrO₂ doped BaTiO₃ were tetragonal and of cubic symmetry. Increase in ZrO₂ content in the BaTiO₃ caused to increase of the lattice parameter and crystallite size of the perovskite structure. The evolution of the Raman spectra was studied for various compositions and the spectroscopic signature of the corresponding phase was determined. The scanning electron microscope was used to investigate the microstructure and surface morphology of the sintered samples. Scanning electron microscope observations revealed enhanced microstructural uniformity and retarded grain growth with increase of ZrO₂ content. Dielectric characteristics of ZrO₂ doped barium titanate were studied using a Hioki 3532-50 LCR meter in the frequency range of 1 kHz-1 MHz. It is found that the dielectric constant (ε_{r}) increases while the dielectric loss (tan δ) decreases with increase in zirconium oxide content (x<0.3).

18

Radiation Effects in DMAAS:Cr Ferroelectric Crystal

80%

Kapustianik V., Czapla Z., Eliyachevskyy Y., Korchak Y., Kulyk B., Rudyk V.

Acta Physica Polonica A

|

2003

|

vol. 104

|

issue 6

571-580

EN

This paper presents the results of investigations of the radiation effects in NH_2(CH_3)_2Al(SO_4)_2×6H_2O crystals doped with chromium. On the basis of absorption spectroscopy and resonance Raman scattering study it has been shown that comparatively low doses of radiation first of all causes recharging of Cr^{3+} on Cr^{4+} ions. Besides, the processes of dehydrogenation and the changes in arrangement of the hydrogen bond network were observed. These changes are followed by distortion of the complexes bonded by such a type of bonds.

19

Barium Strontium Bismuth Niobate Layered Perovskites: Dielectric, Impedance and Electrical Modulus Characteristics

80%

Dasari M., Sambasiva Rao K., Murali Krishna P., Gopala Krishna G.

Acta Physica Polonica A

|

2011

|

vol. 119

|

issue 3

387-394

EN

SrBi_2Nb_2O_9 (SBN) is a bismuth layered perovskite compound, due to its relatively high Curie temperature, has potential application as high ceramic transducer. Also, it is an attractive ferroelectric material that is being considered in non-volatile random access memory cells. Present article describes preparation, dielectric, impedance and modulus characteristics. Temperature and frequency dependence of dielectric permittivity, impedance and electric modulus of barium strontium bismuth niobate (Ba_{0.1}Sr_{0.9}Bi_2Nb_2O_9, BSBN) have been studied in the range of 35-590°C and 45 Hz-5 MHz, respectively. The structural analysis of compound revealed orthorhombic at room temperature. Complex impedance Cole-Cole plots are used to interpret the relaxation mechanism. These plots shows the relaxation behavior as non-Debye type. By using the Cole-Cole plots grain and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in BSBN have been discussed. DC and AC conductivity measurements have been performed on BSBN.

20

Phase Transitions and Fundamental Ferroelectric Dispersion in DMAAl_{1-x}Cr_{x}S Crystals

80%

Kapustianyk V., Eliyashevskyy Y., Czapla Z., Dacko S., Czupiński O., Rudyk V., Serkiz R., Sereda S., Semak S.

Acta Physica Polonica A

|

2015

|

vol. 127

|

issue 3

791-794

EN

This paper presents the results of investigations of the temperature dependence of heat capacity and dielectric dispersion in the vicinity of ferroelectric-ferroelastic phase transition of dimethylammonium metal sulphate hexahydrate crystals DMAAl_{1-x}Cr_{x}S. In particular, it is shown that the isomorphous substitution of metal ion noticeably changes the temperature of phase transition and parameters of the fundamental ferroelectric dispersion observed around T_{c1}. These changes are explained in terms of clusters sizes and dynamics in the framework of order-disorder type phase transition mechanism.

Refine search results

Effects of B₂O₃ Addition on the Sintering Behavior of 0-5-10% ZrO₂ Doped BaTiO₃ Based Ceramics

^1H NMR Study of Molecular Dynamics of 4-apyH Cation under High Hydrostatic Pressure

Peculiarities of Dielectric Relaxation in DMAAS Ferroelectric Crystals

The Pb(Fe_{1/2}Nb_{1/2})O_3 Ferroelectromagnetic Ceramics in a View of Possibilities to be Used for Electric Transducers

Electrical Charge Transfer in Complex Oxides

Dielectric and Electrooptic Investigations of B Phases οf Banana-Shaped Thioesters

Influence of the sample orientation in Sn2P2S6 crystals on the hydrostatic piezoelectric coefficients

The Influence of Partial Isomorphic Substitution on Electronic and Optical Parameters of ABSO₄ Group Crystals

Electronic Structure of BiFeO₃ in Different Crystal Phases

Characterization of Barium Titanate Ceramic Powders by Raman Spectroscopy

Polarization Induced Effects in AlGaN/GaN Heterostructures

Impedance Spectra of As-Grown and Heat Treated Na_{0.5}Bi_{0.5}TiO₃ Crystals

In situ Investigation of OH^{-} Absorption in LiNbO_{3} and LiNbO_{3}:MgO Crystals during Reducing/Oxidizing Annealing

Vibronic Magnetoelectric Effects in the Bi-Based Multiferroics

Modes Orthogonality of the Mechanical System Simple Supported Beam-Actuators-Concentrated Masses

Electrical, Electromechanical and Piezoelectric Properties of Ca₃TaGa₃Si₂O₁₄ Resonators at Elevated Temperatures

Influence of ZrO₂ Addition on the Structure and Dielectric Properties of BaTiO₃ Ceramics

Radiation Effects in DMAAS:Cr Ferroelectric Crystal

Barium Strontium Bismuth Niobate Layered Perovskites: Dielectric, Impedance and Electrical Modulus Characteristics

Phase Transitions and Fundamental Ferroelectric Dispersion in DMAAl_{1-x}Cr_{x}S Crystals