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1.
The structural and electrophysical characteristics of a series of solid solutions of layered perovs-kite-like oxides Bi6 ? x Sr x Ti2 ? x Nb2 + x O18 (x = 0, 0.25, 0.5, 1.0, 1.5, 2.0) have been studied. The temperature dependences of the relative permittivity ?/?0(T) and dielectric loss tangent tanδ have been measured. The dependences of the maximum of the permittivity ?/?0, Curie temperature T C, lattice parameters, and the unit cell volume on x have been obtained. The structural parameter a, which corresponds to the polar direction, and the value of the orthorhombic distortion of the unit cell have been found to demonstrate noticeable negative deviations from the Vegard’s law. It has been established that the variations of the orthorhombic distortion correlate with the variations of the permittivity maximum; however, they do not markedly influence the Curie temperature that varies linearly over entire range of changes in x. 相似文献
2.
《Current Applied Physics》2014,14(1):46-52
The phase assemblage, crystal structure evolution and microwave dielectric response of (Ca0.5+xSr0.5−x)[(Al0.5Nb0.5)0.5Ti0.5]O3 ceramics (abbreviated as CSANT hereafter) are investigated. Single perovskite solid solution is formed in the CSANT ceramics in Sr-rich composition range of x < −0.05, however, Ca4Ti3O10-type layered perovskite phase begins to segregate after x = −0.05. The CSANT perovskites crystallized in Fm3m cubic symmetry in the composition range of x ≤ −0.2, however, as the Ca2+ content in A-site increased, the oxygen octahedral began to be anti-phase tilted at x = −0.1 and the crystal structure transited to P21/n pseudo-orthorhombic space group thereafter. The microwave dielectric response of the CSANT ceramics is elaborately discussed in terms of their crystallographic structure and chemical composition. When sintered at 1500 °C for 4 h, a dielectric constant ɛr of 52.5, a Qf product of 28000 GHz and a τf of +25.4 ppm/°C microwave dielectric ceramic can be obtained in the CSANT ceramics at x = 0.3. 相似文献
3.
S. N. Kallaev Z. M. Omarov R. G. Mitarov A. R. Bilalov G. G. Gadzhiev L. A. Reznichenko R. M. Ferzilaev S. A. Sadykov 《Physics of the Solid State》2014,56(7):1412-1415
The heat capacity and the permittivity of multiferroics Bi1 ? x Gd x FeO3 (x = 0, 0.05, 0.10, 0.15, 0.20) have been studied in the temperature range 130–800 K. It has been found that insignificant substitution of gadolinium for bismuth markedly shifts the temperature of antiferromagnetic phase transition and increases the heat capacity over a wide temperature range. It has been shown that the temperature dependence of the excess heat capacity is due to the manifestation of three-level states. Additional anomalies characteristic of the phase transitions have been revealed in the temperature dependences of the heat capacity for the compositions with x = 0.1 and 0.15 at T ≈ 680 K and T ≈ 430 K, respectively. The results of studies of the heat capacity have been discussed simultaneously with the data of structural studies. 相似文献
4.
E.M. Dutkiewicz J. Suchanicz V. Bovtun K. Konieczny P. Czaja K. Kluczewska 《Phase Transitions》2016,89(7-8):823-828
ABSTRACTThermal expansion, Raman and dielectric properties of the lead-free (1?x)Na0.5Bi0.5TiO3-xSrTiO3 (x = 0, 0.08 and 0.1) ceramic solid solutions, fabricated by the conventional solid-state reaction method, were investigated. The Sr-doping results in an increase of the dielectric permittivity, broadening of the permittivity maximum, enhancement of the relaxation near depolarization temperature, broadening of the Raman bands and shift of all anomalies toward lower temperatures. The observed effects are attributed to an increase of the degree of cationic disorder and enhancement of the relaxor-like features. Anomalies in the thermal expansion strain were observed at the temperatures corresponding to the dielectric anomalies but not related to any phase transitions. These anomalies are supposed to follow changes of the averaged unit cell volume in the temperature interval of tetragonal and rhombohedral phase coexistence. 相似文献
5.
High-quality, large-size lead-free (1 – x)Na0.5Bi0.5TiO3–xBaTiO3 ((1 – x)NBT–xBT) single crystals (x = 0, 0.025, 0.0325 and 0.05) were grown using the Czochralski method. Dielectric and transmitted light intensity properties were measured for these crystals. The broad anomalies exhibited in the temperature dependence of the transmitted light corresponded to structural and dielectric anomalies and were related to the temperature dependence of polar regions and the appearance of a long-range ferroelectric state. We explain our results based on local electromechanical fields, by inhomogeneity of the ion distribution and the mismatch in ion size. We suggested that the NBT–BT system can be a promising lead-free piezoelectric material for ultrasonic delay-line applications, broadband transducers and sensors. 相似文献
6.
Ya. V. Baklanova N. A. Zhuravlev L. G. Maximova T. A. Denisova O. N. Leonidova A. A. Raskovalov N. V. Tarakina 《Bulletin of the Russian Academy of Sciences: Physics》2014,78(4):320-322
Complex lithium metallates Li2 Me x Zr1 ? x O3 ? δ (Me = Nb, Ti, x = 0.05, 0.1) with iso-and heterovalent substitutions for Zr4+ ions in lithium zirconate are synthesized for the first time using a citrate technique. The inclusion of Ti4+ and Nb5+ ions in the crystal structure of Li2ZrO3 is confirmed by means of X-ray diffraction and NMR. It is shown that in the temperature range of 750–820 K, Li2Ti0.1Zr0.9O3 solid solution has higher conductivity than phases of undoped lithium zirconate. 相似文献
7.
Ambrish Kumar Srivastava 《Molecular physics》2014,112(21):2820-2826
In this work, a density functional survey on manganese oxyfluoride (MnOxFy) species for x + y = 1–4 is performed, in which an Mn atom interacts simultaneously with O as well as F atoms. The stabilities of all these species are established against dissociation to manganese oxides as well as fluorides and their relative stabilities are also discussed. It is revealed that the most favourable oxidation state of Mn is +4 in its oxyfluorides, same as in fluorides. For the first time, the superhalogen properties of MnOF3, MnO3F and MnO2F2 species are introduced on the basis of their high electron affinities as compared to halogens. The interaction of MnO2F2 superhalogen with an alkali metal (K) is considered via F atoms as well as O atoms which is similar to that in KF and leads to the formation of stable KMnO2F2 complex. Thus, this study is expected to motivate theorist to design a new series of superhalogen species using transition metals with mixed F and O ligands, as well as experimentalists to synthesise such novel complex compounds. 相似文献
8.
V. V. Sikolenko V. V. Efimov I. O. Troyanchuk D. V. Karpinskii 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(5):713-717
The crystal structure and magnetic properties of a system of Pr0.5Sr0.5Co1 ? x Mn x O3 solid solutions were studied by neutron diffraction and magnetization measurements. It is shown that, at a low manganese concentration, the structure can be described by the I/2a monoclinic space group; with increasing substitution level x the structure becomes orthorhombic. For x > 0.9 the crystal structure is tetragonal at high temperatures and the symmetry is lowered to orthorhombic with lowering the temperature. The substitution of cobalt for manganese leads to the destruction of long-range ferromagnetic order near x ?? 0.25. A transition from the high-temperature ferromagnetic phase to the A-type low-temperature antiferromagnetic phase is observed at x ?? 0.93 in the temperature range 110?C160 K. 相似文献
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11.
G. I. Makovetski? S. S. Dorofe?chik T. M. Tkachenko O. F. Demidenko 《Physics of the Solid State》2009,51(3):537-539
Solid solutions in the (Mn1 ? x Fe x )1.68Sn system (x ≤ 0.5) with a Ni2In-type structure are synthesized by the solid-phase reaction method in a stepwise temperature regime. The unit cell parameters a and c decrease with an increase in the iron concentration in the alloys and become equal to a = 0.430 nm and c = 0.538 nm for the (Mn0.5Fe0.5)1.68Sn alloy. A superstructure with the unit cell parameters a ss = 3a and c ss = c is revealed in alloys of the system under investigation. The specific magnetization of the alloys increases nonlinearly from 53 G cm3 g?1 in the Mn1.68Sn alloy to 72 G cm3 g?1 in the (Mn0.5Fe0.5)1.68Sn solid solution. The Curie temperature changes from 270 K in the initial alloy of the composition Mn1.68Sn to 365 K in the alloy of the composition (Mn0.5Fe0.5)1.68Sn. All solid solutions in the (Mn1 ? x Fe x )1.68Sn (x ≤ 0.5) system exhibit metallic conductivity in the temperature range from 77 to 450 K. 相似文献
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13.
《Surface science》1989,223(3):L913-L919
The structures and binding energies of small boron-rich clusters are studied using correlated wave functions and polarization basis sets. Carbon is the central atom in CBn+, while SiBn+ prefers planar boron networks with silicon as one of the edge atoms. These ground state structures can be explained by differences in the electronegativities of the component elements. The various fragmentation channels of SiBn+ are also examined using binding energy differences. 相似文献
14.
The real and imaginary parts of the magnetic permeability at frequencies of 0.1, 1.0, and 10.0 kHz, as well as the electron paramagnetic resonance (EPR) line width and g-factor, have been measured in Sm x Mn1 ? x S (0.10 < x < 0.25) solid solutions in the temperature range 5–300 K. The logarithmic dependence of the maximum in the imaginary part of the magnetic permeability on the frequency and the power-law dependence of Imμ on the temperature have been determined. The mechanism of relaxation of the magnetic moment in the magnetically ordered and paramagnetic phases has been established. The experimental results have been explained in terms of the Heisenberg model with competing exchange interactions and the formation of the antiaspiromagnetic state at low temperatures. 相似文献
15.
N. M. Olekhnovich I. I. Moroz A. V. Pushkarev Yu. V. Radyush A. N. Salak N. P. Vyshatko V. M. Ferreira 《Physics of the Solid State》2008,50(3):490-495
The dielectric properties of (1 ? x)Na1/2Bi1/2TiO3-xLaMg1/2Ti1/2O3 solid solutions (0 ≤ x ≤ 0.4) were studied over the temperature range 650–1030 K by measuring the impedance spectra over the frequency range 25–106 Hz. The Curie temperature T C was determined as a function of the composition of the solid solutions. It is shown that T C decreases linearly with increasing x. The temperature dependences of the dc component (σdc) and the polarization component (σ′ac) of the real part of the conductivity are found. The activation energy for the conductivity σdc is shown to increase abruptly as the temperature increases above approximately 770 K for all solid solution compositions. Over the temperature range corresponding approximately to the region of existence of the tetragonal phase of Na1/2Bi1/2TiO3, the polarization component σ′ac of the solid solutions, as well as that of the pure compound, is anomalously high at low frequencies, which can be due to structural inhomogeneities. 相似文献
16.
P. Yu. Teslenko A. G. Razumnaya V. O. Ponomarenko A. G. Rudskaya A. V. Nazarenko A. S. Anokhin M. V. Avramenko D. I. Levshov M. F. Kupriyanov Yu. I. Yuzyuk 《Physics of the Solid State》2014,56(9):1866-1871
The structures and the dynamic characteristics of the lattices of two compositions of solid solutions of multiferroic BiFeO3 with ferroelectric KNbO3 and antiferroelctric NaNbO3, namely, (1 ? x)BiFeO3-xKNbO3 and (1 ? x)BiFeO3-xNaNbO3, have been studied using X-ray powder diffraction and Raman spectroscopy. For these systems with x = 0.3, 0.5, and 0.7, the symmetry and unit cell parameters at room temperature have been determined. An analysis of the vibrational spectra has revealed sequences of rotational distortions with variations in the concentrations of components. 相似文献
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18.
《Chinese Journal of Physics (Taipei)》2018,56(6):2958-2966
Sm2O3, Gd2O3, Eu2O3 triple-doped Bi2O3 based quaternary solid solutions were synthesized as a candidate electrolyte material using the solid-state reaction technique. The structural, thermal and electrical conductivity features of the ceramic samples were examined and compared by using X-ray powder diffraction (XRD), thermal gravimetry/differantial thermal analysis (TG/DTA) and the four-point probe technique (4PPT). The result of XRD measurements indicated that the (Bi2O3)(1−x−y−z)(Gd2O3)x(Sm2O3)y(Eu2O3)z (x = 10/y = 10/z = 5, 15, 20 mol % and x = 10/y = 5, 10, 15, 20/z = 10 mol %) samples have a stable face-centered cubic δ-phase and mixed phase crystallographic structure. The phase stability was also checked by the DTA evaluations results. The temperature dependent electrical conductivity measurements showed that the highest electrical conductivity was observed for the sample of the (Bi2O3)0.75(Gd2O3)0.10(Sm2O3)0.05(Eu2O3)0.10 system which has a stable and δ-phase was found as 6.67 × 10−3 (Ω cm)−1 at 650 °C. This sample can be used as an electrolyte material in the solid oxide fuel cells (SOFCs) which is possible to operate at intermediate temperature ranges. The activation energy was also calculated at a low temperature range (350–650 °C) and high temperature range (above 650 °C). The values for the samples vary from 0.63 eV to 1.08 eV at low temperature and at high temperature they vary from 0.43 eV to 0.75 eV. 相似文献
19.
Studies on (Y1 - xLa X )Ba2Cu3O7, x = 0.0 - 1.0, in steps of 0.1, have been carried out. Results show that for x ≤ 0.4, orthorhombicity and high Tc of 90 K are retained. Tc decreases gradually for x ≥ 0.4. Pure LaBa2Cu3O7 shows a TC ZERO of 73 K. XRD data do not reveal any clearcut orthorhombic distortion for pure LaBa2CuO7 after annealing at 350°C for 4 days. 相似文献
20.
Sheleg A. U. Hurtavy V. G. Shautsova V. V. Aliev V. A. 《Physics of the Solid State》2012,54(3):622-625
This paper reports on a study of the dielectric permittivity and electrical conductivity of single-crystal TlInS
x
Se2 − x
solid solutions as functions of temperature and composition. It has been found that the dielectric permittivity ɛ and electrical
conductivity σ decrease with increasing x and increase with growing temperature. The temperature dependences ɛ = f(T) and σ = f(T) for TlInS
x
Se2 − x
crystals have been demonstrated to reveal anomalies in the form of maxima, which suggests that these crystals undergo phase
transitions. The temperatures of the phase transitions increase with increasing x. 相似文献