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1.
Single crystals of Cs3Bi2I9 have been grown. Polarized-optical, dielectric, and calorimetric studies have been performed, along with measurements of
birefringence, and the coefficients of elasticity c
44, and linear expansion a over a wide temperature range. It is found that an intrinsic (pseudo-intrinsic) second-order phase
transition to the ferroelastic phase takes place at T
0=220.0±0.6 K accompanied by a change of the crystal symmetry from 6/mmc to 2/m. The transition parameter depends linearly on the shear strain x
5 and varies with temperature according to a power law with exponent β=0.5.
Zh. éksp. Teor. Fiz. 39, 1850–1852 (October 1997) 相似文献
2.
I. P. Aleksandrova A. A. Sukhovskii S. V. Mel’nikova L. I. Shabanova A. I. Zaitsev J. J. Melero J. Bartolomé 《Physics of the Solid State》1997,39(5):846-848
A sequence of two phase transitions at 85.3±0.6 K and 72.6±0.4 K is observed in hexagonal Cs3Sb2I9. The NQR spectra of 127I are analyzed, optical polarization studies are made, and the thermal properties, linear expansion coefficients, and stiffness
constants are measured over a broad range of temperatures below room temperature.
Fiz. Tverd. Tela (St. Petersburg) 39, 946–948 (May 1997) 相似文献
3.
I.P. Aleksandrova R. Burriel J. Bartolome B.Sh. Bagautdinov J. Blasco A.A. Sukhovsky 《Phase Transitions》2013,86(6):607-620
The trigonal (P-3 m1) modification of Cs 3 Bi 2 Br 9 and Cs 3 Sb 2 I 9 have been studied using NQR, X-ray single crystal and powder pattern methods. Moreover, the heat capacity was measured in a wide temperature interval: 4-300 K. In Cs 3 Bi 2 Br 9 a second-order phase transition was found at T C = 96 K. The low-temperature phase is monoclinic (C12/c1), with the unit cell doubled along the [001] direction. Cs 3 Sb 2 I 9 has a sequence of phase transitions at T C = 85 K, T i = 78 K and T L = 72.1 K. The monoclinic structure below 85 K is isomorphic with the low-temperature structure of Cs 3 Bi 2 Br 9 . According to calorimetric data the lock-in transition at 72.1 K is discontinuous. 相似文献
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Raman and IR spectra of Bi2W2O9, the m = 2 member of the cation‐deficient Aurivillius phase, have been measured. The obtained spectra are discussed using the factor group approach for the orthorhombic Pna21(C2v9) space group. The results are compared with those obtained for Bi2WO6 and some m = 2 members of Aurivillius family of bismuth layered ferroelectrics. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
6.
Grenier B Inagaki Y Regnault LP Wildes A Asano T Ajiro Y Lhotel E Paulsen C Ziman T Boucher JP 《Physical review letters》2004,92(17):177202
Field-induced magnetic order has been investigated in detail in the interacting spin 3/2 dimer system Cs3Cr2Br9. Elastic and inelastic neutron scattering measurements were performed up to H=6 T, well above the critical field H(c1) approximately 1.5 T. The ordering displays incommensurabilities and a large hysteresis before a commensurate structure is reached. This structure is fully determined. Surprisingly, the lowest excitation branch never closes. Above H(c1), the gap increases slowly with the field. An analysis in terms of projected pseudospins is given. 相似文献
7.
Stability,electronic structure,and optical properties of lead-free perovskite monolayer Cs3B2X9(B=Sb,Bi;X=Cl,Br,I)and bilayer vertical heterostructure Cs3B2X9/Cs3B’2X9(B,B’=Sb,Bi;X=Cl,Br,I) 下载免费PDF全文
The lead-free perovskites Cs3B2X9(B=Sb,Bi;X=Cl,Br,I)as the popular photoelectric materials have excellent optical properties with lower toxicity.In this study,we systematically investigate the stable monolayer Cs3B2X9and bilayer vertical heterostructure Cs3B2X9/Cs3B02X9(B,B0=Sb,Bi;X=Cl,Br,I)via first-principles simulations.By exploring the electrical structures and band edge positions,we find the band gap reduction and the band type transition in the heterostructure Cs3B2X9/Cs3B02X9 due to the charge transfer between layers.Furthermore,the results of optical properties reveal light absorption from the visible light to UV region,especially monolayer Cs3Sb2I9 and heterostructure Cs3Sb2I9/Cs3Bi2I9,which have absorption peaks in the visible light region,leading to the possibility of photocatalytic water splitting.These results provide insights for more two-dimensional semiconductors applied in the optoelectronic and photocatalytic fields. 相似文献
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R. A. Brand G. Le Caër J. -M. Dubois F. Hippert Ch. Sauer J. Pannetier 《Hyperfine Interactions》1990,54(1-4):473-478
Recently we have studies β-Al9Si(Mn1?x Fe x )3 using Mössbauer effect spectroscopy withx=0.28 and discovered a new transition at about 80 K. Neutron diffraction studies down to low temperatures reveal no structural changes, so that this transition at 80 K is indeed of magnetic origin. The magnetic susceptibility shows a small maximum near this temperature superimposed on a large Curie-like background. In addition to this transition, the Curie-like background shows a cusp near 4 K. We thus infer a magnetic double transition in this disordered alloy. These magnetic transitions have been followed to lower Fe concentrations (x=0.10 and 0.20) by both Mössbauer spectroscopy (T c ) and by magnetic susceptibility (T g). It is found thatT C decreases rapidly with decreasing Fe concentration, whileT g remains relatively constant. The saturation hyperfine fieldB hf(0) decreases rapidly with decreasingx, indicating that the Fe atoms loose their magnetic moments in the limit of infinite dilution, and the important role played by Fe?Fe nearest neighbors in determining the magnetic properties. 相似文献
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Angst M Hermann RP Schweika W Kim JW Khalifah P Xiang HJ Whangbo MH Kim DH Sales BC Mandrus D 《Physical review letters》2007,99(25):256402
The temperature dependence of charge order in Fe2OBO3 was investigated by resistivity and differential scanning calorimetry measurements, M?ssbauer spectroscopy, and synchrotron x-ray scattering, revealing an intermediate phase between room temperature and 340 K, characterized by coexisting mobile and immobile carriers, and by incommensurate superstructure modulations with temperature-dependent propagation vector (1/2, 0, tau). The incommensurate modulations arise from specific antiphase boundaries with low energy cost due to geometrical charge frustration. 相似文献
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Friedrich A Biehler J Morgenroth W Wiehl L Winkler B Hanfland M Tolkiehn M Burianek M Mühlberg M 《J Phys Condens Matter》2012,24(14):145401
The high-pressure behaviour of Bi2Fe4O9 was analysed by in situ powder and single-crystal x-ray diffraction and Raman spectroscopy. Pressures up to 34.3(8) GPa were generated using the diamond anvil cell technique. A reversible phase transition is observed at approximately 6.89(6) GPa and the high-pressure structure is stable up to 26.3(1) GPa. At higher pressures the onset of amorphization is observed. The crystal structures were refined from single-crystal data at ambient pressure and pressures of 4.49(2), 6.46(2), 7.26(2) and 9.4(1) GPa. The high-pressure structure is isotypic to the high-pressure structure of Bi2Ga4O9. The lower phase transition pressure of Bi2Fe4O9 with respect to that of Bi2Ga4O9 (16 GPa) confirms the previously proposed strong influence of cation substitution on the high-pressure stability and the misfit of Ga3+ and Fe3+ in tetrahedral coordination at high pressure. A fit of a second-order Birch–Murnaghan equation of state to the p–V data results in K0 = 74(3) GPa for the low-pressure phase and K0 = 79(2) GPa for the high-pressure phase. The mode Grüneisen parameters were obtained from Raman-spectroscopic measurements. 相似文献
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Fedir V. Motsnyi Oleksandr M. Smolanka Evgen Yu. Peresh 《Solid State Communications》2006,137(4):221-224
For the first time we have found a new giant thermodynamical optical effect near the ferroelastic phase transition point in Cs3Bi2I9 layered crystal. The effect is appeared as periodical oscillations in time of the reflection coefficient. This phenomenon is caused by the small temperature deviations in thermodynamical system the appearance of which in the reflection spectra is strongly amplified in the ferroelastic phase transition point. The optical oscillations are explained on the base of a model that takes into account the temperature dependence of the refractive index through the order parameter (spontaneous strain) of the crystal. 相似文献
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Powder samples of hydrothermally grown Cr 3+ -doped Cs 2 NaGaF 6 crystals have been investigated with electron paramagnetic resonance spectroscopy at X - (9.5 v GHz) and Q -band (34 v GHz). Analysis of the spectra clearly demonstrates that there are two distinct Cr 3+ centres in the Cs 2 NaGaF 6 crystal, having nearly identical g factors, but differing largely from the viewpoint of their zero field splitting. By using the 53 Cr hyperfine spectra observed with electron nuclear double resonance spectroscopy, it is deduced that these centres have opposite signs for the zero field splitting. The spectroscopic properties of the Cr 3+ centres in the isostructural Cs 2 NaGaF 6 and Cs 2 NaAlF 6 crystals are compared and discussed. 相似文献
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2D and 3D electrically switchable hexagonal photonic crystal in the ultraviolet range 总被引:1,自引:0,他引:1
Two holographic lithography systems are demonstrated for easy and large-area fabrication of 2D and 3D photonic crystal (PhC)
microstructures in a polymer dispersed liquid crystal (PDLC) by applying a single top-cut hexagon prism. A six-beam system
has been used to produce 2D hexagonal PhCs. By adding an additional mirror, a twelve-beam system is demonstrated to fabricate
3D PhCs with ultraviolet (UV) band-gap along the z direction. A good agreement is obtained for measured PhCs structure and
theoretical results. Far-field diffraction patterns and electrical switching characteristics of the 2D and 3D PhC HPDLC films
have been investigated.
PACS 42.15.Eq; 42.40.Eq 相似文献
18.
Paturzo M De Natale P De Nicola S Ferraro P Mailis S Eason RW Coppola G Iodice M Gioffré M 《Optics letters》2006,31(21):3164-3166
An optical phase array with tunable phase step is demonstrated. The phase array consists of a two-dimensional hexagonal lattice of inverted ferroelectric domains fabricated on a Z-cut lithium niobate substrate. The electro-optically tunable phase step is obtained by the application of an external electric field along the z axis of the crystal via transparent electrodes. Theoretical analysis and experimental results are presented, showing that a tunable and flexible adaptive optical illuminator device can be realized by combining the electro-optic tunability with the Talbot effect. Generation of a multiplicity of light patterns is shown. 相似文献
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