共查询到20条相似文献,搜索用时 0 毫秒
1.
The dielectric properties of the ceramics of (1 − x)BiFeO3 − x(KBi)1/2TiO3 (0.40 < x < 0.85) solid solutions with an orthorhombic structure have been studied using impedance spectroscopy in the frequency range
25–106 Hz at different temperatures. It has been shown that these solid solutions undergo a diffuse ferroelectric phase transition.
The Curie temperature is found to be in the range 620–640 K. The activation energies of dielectric polarization relaxation
(δE
M
) and dc charge carriers (ΔE
dc) are determined. It has been established that, in the vicinity of 460 K, ΔE
dc increases jumpwise as the temperature increases. 相似文献
2.
M. V. Gorev I. N. Flerov Ph. Sciau S. Guillemet-Fritsch 《Physics of the Solid State》2009,51(4):790-796
Deformation and the thermal expansion coefficient of ceramic samples of (Ba1 − x
La
x
)Ti1 − x/4O3 solid solutions (x = 0, 0.026, 0.036, 0.054) were studied in the temperature range 120–700 K. Based on an analysis of the data obtained, the
temperature-composition phase diagram is refined, and the temperature dependence of the polarization is calculated. The results
are discussed in combination with the dielectric measurement data.
Original Russian Text ? M.V. Gorev, I.N. Flerov, Ph. Sciau, S. Guillemet-Fritsch, 2009, published in Fizika Tverdogo Tela,
2009, Vol. 51, No. 4, pp. 746–752. 相似文献
3.
4.
D. S. L. Pontes E. Longo F. M. Pontes M. S. Galhiane L. S. Santos Marcelo A. Pereira-da-Silva J. H. D. da Silva A. J. Chiquito P. S. Pizani 《Applied Physics A: Materials Science & Processing》2009,96(3):731-740
Ferroelectric Pb1−x−y
Ca
x
Sr
y
TiO3 thin films (denoted by PCST90, PCST70, and PCST30) were deposited on the Pt/Ti/SiO2/Si substrates by a chemical solution deposition method. Their properties were investigated from the viewpoint of crystal
structure, microstructure, dielectric, and ferroelectric properties. X-ray diffraction patterns revealed the formation of
PCST90, PCST70, and PCST30 thin films without any secondary phases. Infrared and Raman spectroscopy results show that a gradual
phase transition from tetragonal to pseudocubic or cubic perovskite structure may occur in PCST thin films with the simultaneous
increase of Ca2+ and Sr2+ contents. Both substitution of isovalent Ca2+ and Sr2+ at Pb2+-site enhanced the dielectric constant and reduced the remnant polarization. In addition, ferroelectric test analyses show
that the PCST thin films undergo a ferroelectric-to-paraelectric phase transformation with an amount of Pb2+, Ca2+, and Sr2+ at 30%, 35%, and 35% mol, respectively. Hence, the absence of ferroelectric property may be attributed to a decreasing of
the octahedron distortion in the perovskite structure accompanied by a weakening of long-range ferroelectric order. 相似文献
5.
I. O. Troyanchuk A. N. Chobot N. V. Tereshko O. S. Mantytskaya E. A. Efimova 《Physics of the Solid State》2011,53(7):1340-1347
The magnetic and magnetotransport properties of Pr0.5Sr0.5Mn1 − x
Co
x
O3 (x ≤ 0.5) solid solutions have been investigated using neutron diffraction methods. The magnetization and electrical conductivity
have been measured in magnetic fields up to 140 kOe. It has been established that, during cooling in the temperature range
from 160 to 110 K, the compounds of compositions with a cobalt content x ≤ 0.07 undergo a structural phase transition from the high-temperature ferromagnetic phase to the antiferromagnetic phase.
A further substitution of cobalt for manganese leads to a stabilization of the inhomogeneous dielectric ferromagnetic state,
whereas a state of the cluster spin-glass type has been revealed in compositions with x = 0.15 and 0.20. At x ≥ 0.25, a new magnetic phase with a Curie temperature up to 210 K is formed as a result of the magnetic interaction between
manganese and cobalt ions. A magnetic phase diagram of the system under investigation has been constructed. 相似文献
6.
I. O. Troyanchuk D. V. Karpinsky M. V. Bushinskii O. Prokhnenko M. Kopcevicz R. Szymczak J. Pietosa 《Journal of Experimental and Theoretical Physics》2008,107(1):83-89
Systems of solid solutions Bi1 − x
Ca
x
FeO3 (I) and Bi1 − x
CaxFeO1 − x
Ti
x
O3 (II) have been obtained and their properties have been studied using neutronography and M?ssbauer spectroscopy; magnetization
and permittivity have been measured. It is shown that an increase in the concentration of calcium ions in system I for x > 0.2 changes rhombohedral distortions of a unit cell (space group R3c) to tetragonal distortions (space group I4/mcm), while rhombohedral distortions in system II for x > 0.2 are replaced by orthorhombic distortions (space group Pnma). Analysis of the crystal structure has revealed strong anisotropy in vibrations of Bi and O ions in system I compounds.
Systems I and II are characterized by G-type antiferromagnetic ordering of magnetic moments. In system II, spontaneous magnetization
associated with the Dzyaloshinskii-Moriya interaction has been detected. According to M?ssbauer spectroscopy data, iron ions
in compounds I and II are in the trivalent state and charge compensation occurs due to the formation of oxygen vacancies.
The permittivity increases with the calcium concentration.
Original Russian Text ? I.O. Troyanchuk, D.V. Karpinsky, M.V. Bushinskii, O. Prokhnenko, M. Kopcevicz, R. Szymczak, J. Pietosa,
2008, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2008, Vol. 134, No. 1, pp. 105–112. 相似文献
7.
I. A. Boiaryntseva A. V. Gektin G. B. Stryganyuk V. N. Baumer A. N. Belsky 《Journal of Applied Spectroscopy》2012,79(4):589-594
Luminescence spectra of Ca0.65Pr0.35F2.35 solid solutions are studied. It is found that, depending on the excitation energy, different kinds of emission centers appear
in these spectra. An interconfigurational 4f 15d1 →4f2 luminescence is typical for single Pr3+ ions in tetragonal sites. Data on the structure of the solid solutions show that the emission centers involved in 1S0 → 4f2 transitions can be attributed to Pr3+ ions contained in clusters. 相似文献
8.
N. P. Stepanov A. A. Kalashnikov A. K. Gil’fanov V. M. Grabov Yu. V. Ulashkevich L. D. Ivanova Yu. V. Granatkina 《Optics and Spectroscopy》2011,111(6):912-918
We study IR polarized reflection spectra of solid solutions (Bi2−x Sb x )Te3 (0 < x < 1) in the temperature range 78–293 K and in the excitation range of plasma oscillations of free charge carriers. We reveal that, as the content of Sb2Te3 in the solid solution increases from 0 to 50%, the anisotropy of both plasma frequencies and magnetic susceptibility vary insignificantly. This indicates that, at 293 K, these crystals do not show significant changes in the composition of groups of free carriers near the chemical potential level. We have found that to describe the observed anisotropy of plasma frequencies, it is necessary to take into account the effect of heavy holes of the valence band. This is also confirmed by the results of the study of the temperature behavior of plasma reflection spectra, which exhibit regularities that are similar to anomalous temperature changes of the Hall coefficient. We show that a decrease in plasma frequencies with increasing temperature cannot be described by an increase in the effective mass of charge carriers in accordance with the expression m* ∼ T 0.17, which was obtained upon interpretation of temperature dependences of a number of kinetic coefficients. We use the empirical Moss rule ɛ∞2 E g to estimate the rate of decrease of the thermal band gap dE g /dT = −1.6 × 10−4 eV/deg in a crystal that contains 25% Sb2Te3. 相似文献
9.
Polycrystalline Pb1−x
Sr
x
(Fe0.012Ti0.988)O3 (0.2≤x≤0.4) (PSFT) thin films have been grown on fused quartz substrates by metallo-organic decomposition technique. The grown films
were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), source meter and UV–Vis–NIR spectrophotometer
to determine the structural, microstructural, dc resistivity and optical properties. The XRD pattern confirmed that the PSFT
films has distorted tetragonal single phase, which close to cubic at higher Sr concentration. AFM analysis revealed that the
grains size reduces with increasing Sr concentration and their average values lies in the range of 26–9 nm. The higher values
of dc resistivity of PSFT nano grains indicate that the transmission of light occurs within these grains up to short wavelength.
The refractive index and the extinction coefficient were determined from the optical transmission spectrum in the wavelength
range of 200–1100 nm and compared with that theoretically calculated, when fitted to a single oscillator model. The values
of optical band gap were determined from Tauc’s extrapolation fitting and suggests that the transformation of electrons during
transmission of light through local states within Fermi gap. 相似文献
10.
Phase x-T diagram of actual solid solutions of the (1 ? x )PbZrO3- x PbTiO3 system (0.37 ≤ x ≤ 0.57)
L. A. Reznichenko L. A. Shilkina O. N. Razumovskaya E. A. Yaroslavtseva S. I. Dudkina O. A. Demchenko Yu. I. Yurasov A. A. Esis I. N. Andryushina 《Physics of the Solid State》2008,50(8):1527-1533
Ceramics of PbZr1 − x
Ti
x
O3 solid solutions were systematically studied in the range 0.37 ≤ x ≤0.57. The x-T phase diagram of the system is constructed in the range 25°C ≤ T ≤ 650°C. The diagram has a region of an indefinite symmetry in the vicinity of the transition to the nonpolar cubic phase.
It is established that solid solutions in this region are characterized by weak distortions and temperature-time instability
of the crystal structure. Three concentration regions are separated differing in the value of the jump in the unit cell volume
ΔV at the line of transitions from the rhombohedral (tetragonal) phase to the region of indefinite symmetry. It is revealed
that there are three temperature ranges differing in the behavior of the temperature dependence of the inverse permittivity,
which are due to the existence of two critical Curie points at the boundary separating the ferroelectric phases from the cubic
phase.
Original Russian Text ? L.A. Reznichenko, L.A. Shilkina, O.N. Razumovskaya, E.A. Yaroslavtseva, S.I. Dudkina, O.A. Demchenko,
Yu.I. Yurasov, A.A. Esis, I.N. Andryushina, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 8, pp. 1469–1475. 相似文献
11.
Kuldeep Chand Verma R. K. Kotnala N. S. Negi 《Applied Physics A: Materials Science & Processing》2009,96(4):1009-1015
The effect of nanosize grains to enhance dielectric tunability in chemically prepared (Pb1−x
Sr
x
)TiO3 (PST) (x=0.1 to 0.5) thin films has been observed. The grain size is evaluated from X-ray diffraction patterns and atomic force microscopy.
The average grain size lies in the range of 80–23 nm with varying Sr content. The nanosize grains in the PST films control
the dielectric behavior up to the higher frequency region and exhibit large tunability with low loss factor at room temperature.
The current–voltage characteristics show a large tunability as electron transport takes place within a highly resistive Fermi
gap. 相似文献
12.
O. M. Fedorova A. M. Jankin L. B. Vedmid G. A. Dorogina I. A. Zvereva 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(8):1159-1160
The mechanisms of formation of NdSr2− x
Ca
x
Mn2O7 (0 ≤ x ≤ 2.0) solid solution have been studied. The dependence of its volume magnetic susceptibility on the calcium concentration
is obtained. The stability of this solid solution is compared with that of similar solid solutions in lanthanum-containing
systems. 相似文献
13.
I. O. Troyanchuk D. V. Karpinsky M. V. Bushinsky M. I. Kovetskaya E. A. Efimova V. V. Eremenko 《Journal of Experimental and Theoretical Physics》2011,113(6):1025-1031
The crystal structure and magnetic and piezoelectric properties of the Bi1 − x
Ca
x
FeO3 − x/2 system (x ≤ 0.2) are studied. The crystal-structure transformations occur in the following sequence: rhombohedral (R3c) polar phase (x ≤ 0.06) → modulated polar phase (0.07 ≤ x ≤ 0.1) → modulated antipolar phase (0.11 ≤ x ≤ 0.14). The modulated polar and antipolar phases are weakly ferromagnetic with a spontaneous magnetization of 0.25 G cm3/g (x = 0.09). In the polar weak ferromagnet with x = 0.09, a uniform piezoelec- tric response 2.5 times stronger than in the initial BiFeO3 compound is detected by the piezoelectric force microscopy. 相似文献
14.
D. V. Shamshur R. V. Parfen’ev A. V. Chernyaev S. A. Nemov 《Physics of the Solid State》2010,52(9):1815-1819
A study is reported of the low-temperature electrophysical (including superconducting) characteristics of the (Pb0.5Sn0.5)1 − x
In
x
Te semiconducting solid solutions with an indium content variable within x = 0.05–0.20. A decrease in the impurity content x in the material has been found to bring about a decrease in the superconducting transition temperature T
c
and the onset of an “insulating” state of the material. These effects manifest themselves in an increase in the low-temperature
(T = 4.2 K) resistivity of (Pb0.5Sn0.5)0.95In0.05Te by more than three orders of magnitude as compared to that of (Pb0.5Sn0.5)0.8In0.2Te. A decrease in the In content in the solid solution also gives rise to a radical change in the shape of the temperature
dependence of the electrical resistivity from a metallic behavior in the material with x = 0.20 (decrease in the electrical resistivity with decreasing temperature in the range 300–4.2 K) to a semiconducting behavior
in a sample with x = 0.05 (exponential increase in the resistivity at T < 25 K). This transition to the insulating state with decreasing content of the impurity should be assigned to the displacement
of the impurity band of quasi-local indium states toward the top of the light-hole valence band of the material and its emergence
into the band gap of the solid solution. 相似文献
15.
E. I. Lakhno E. I. Burmakin I. V. Korzun G. Sh. Shekhtman 《Physics of the Solid State》2012,54(3):504-507
The rubidium monoferrite RbFeO2-based solid solutions with the composition Rb2 − 2x
Fe2 − x
P
x
O4 have been synthesized, and their crystal structure and the temperature and concentration dependences of the total and electron
conductivities have been studied. The introduction of P5+ ions has been found to sharply decrease the electron conductivity that prevails in pure rubidium monoferrite and, at the
same time, to increase the ionic conductivity. The latter becomes dominant as the phosphorus concentration increases. The
maximum rubidium-cation conductivity of the materials under study is ∼3 × 10−2 S/cm at 300°C and ∼3 × 10−1 S/cm at 700°C. The results have been compared with the previously obtained data for similar solid solutions based on rubidium
monogallate and monoaluminate. 相似文献
16.
E. S. Zhukova N. P. Aksenov B. P. Gorshunov Yu. G. Selivanov I. I. Zasavitskii D. Wu M. Dressel 《Physics of the Solid State》2011,53(4):810-814
The spectra of epitaxial Pb1 − x
Eu
x
Te (0 ≤ x ≤ 0.37) solid solution layers grown on BaF2 and Si substrates have been investigated over a wide frequency range 7–4000 cm−1 at temperatures of 5–300 K. Apart from the phonon and impurity absorption lines, the absorption in a local mode in PbEuTe
layers of substrates and buffer layers has been observed in the frequency range 110–114 cm−1. As the temperature decreases from 300 to 5 K, the transverse phonon mode softens from 33.0 to 19.5 cm−1. 相似文献
17.
Investigations of magnetic susceptibility (χ) of (3HgS)1–x
(Al2S3)
x
(x = 0.5) crystals doped with manganese investigated by the Faraday method in the range of Т = 77–300 K and Н = 0.25–4 kOe demonstrate that peculiar magnetic properties can be due to the presence of clusters of the Mn–S–Mn–S type in
these crystals. Based on the investigation of kinetic coefficients of the crystals performed for Т = 77–300 K and Н = 0.5–5 kOe, it is established that the crystals demonstrate conductivity of the n-type, and their electric conduction only
very slightly depends on the temperature and shows a maximum, the Hall coefficient is independent of the temperature, while
the temperature dependences of mobility exhibit a maximum. Using the concentration dependence of the effective electron mass
at the Fermi level, the width of the forbidden band, the matrix element of interatomic interaction, and the effective mass
on the conduction-band bottom are obtained. Based on investigations by optical methods, the presence of direct optical interband
transitions in the crystals is established and the value of the optical forbidden band (at Т = 300 K) is determined. 相似文献
18.
Yu. B. Bolkhovityanov A. K. Gutakovskii A. S. Deryabin L. V. Sokolov 《Physics of the Solid State》2011,53(9):1791-1797
The structure of dislocations in Ge x Si1 − x (x ∼ 0.4–0.8) films grown by molecular beam epitaxy on Si(001) substrates tilted by 6° toward the nearest (111) plane has been studied. The epitaxy of GeSi films on substrates deviating from the exact (001) orientation has allowed us to establish the main mechanism of formation of edge misfit dislocations (MDs), which most effectively (for heterostructures of the given composition) relieve stresses caused by the mismatch between lattice parameters of the film and substrate. Despite the edge MDs being defined as immobile (sessile) dislocations, their formation proceeds according to the gliding mechanism proposed by Kvam et al. [J. Mater. Res. 5, 1900 (1990)]. A comparative estimation of the propagation velocities of the primary and induced 60° dislocations, as well as the resulting 90° MDs, has been performed. It has been established that the condition providing for the most effective edge MD formation by the induced nucleation mechanism is the appearance of 60° MDs in a stressed film immediately after it reached a critical thickness. A source of these dislocations can be provided by a preliminarily grown buffer GeSi layer that occurs in a metastable state at the initial stage of plastic relaxation. 相似文献
19.
A. A. Pavelko A. G. Lutokhin S. I. Raevskaya Yu. N. Zakharov M. A. Malitskaya I. P. Raevskii I. N. Zakharchenko E. I. Sitalo N. A. Korchagina V. G. Kuznetsov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1104-1106
(1 − x)PbFe1/2Nb1/2O3−x
PbTiO3 (PFN-xPT) ferroelectric ceramics with low dielectric loss and pronounced anomalies of dielectric and pyroelectric properties near
the ferroelectric-ferroelectric phase transition was obtained by doping with lithium. The temperature dependence of the position
of the morphotropic boundary between the rhombohedral (monoclinic) and tetragonal phases in the x-T phase diagram of the PFN-xPT system was determined for the first time. 相似文献