Search results for "Ferro"
showing 10 items of 2451 documents
DSC, Dilatometric, Dielectric, and1H NMR Studies of Phase Transitions and Molecular Motions in [N(C2H5)4]3M2Cl9 (M = Sb, Bi) Crystals
1995
Results in the dependence of stoichiometry of obtained tetraethylammonium (TEA) chloroantiomonate and chlorobismuthate salts on the molar ratio of reactants used in the synthesis are presented. Seven tetraethylammonium salts are obtained: (TEA) 6 M 8 Cl 30 , TEAMCI 4 , (TEA) 3 M 2 Cl 9 (M = Sb, Bi) and (TEA) 2 SbCl 5 . Preliminary X-ray diffraction studies on (TEA) 3 M 2 Cl 9 (M = Sb, Bi) show that they are isomorphous, crystallizing at room temperature in monoclinic symmetry. The dilatometric, dielectric, and DSC studies show that (TEA) 3 Bi 2 Cl 9 undergoes two phase transitions at T c2 = 144 K and at T c1 = 322 K while (TEA) 3 Sb 2 Cl 9 undergoes three transitions at T c3 = 185, T c2 = 2…
Ferroelectricity in {N(CH3)4}2ZnI4
1988
Dielectric properties of the {N(CH 3 ) 4 } 2 ZnI 4 crystal were studied between room temperature and 4.2 K. Two phase transitions were seen from dielectric constant anomalies at T 1 =254 K and T c =210 K on cooling. Ferroelectric hysteresis loops were observed along the c -direction below T c with a low frequency applied field of 0.0025 Hz. The spontaneous polarization obtained by pyroelectric charge measurement tended to be 2.5×10 -3 C/m 2 at 0 K.
Crystal structure, phase transition and ferroelectric properties of the [(CH3)3NH]3[Sb2Cl9(1 x)Br9x] (TMACBA) mixed crystals
2003
The paraelectric–ferroelectric phase transition in the [(CH3)3NH]3[Sb2Cl9(1−x) Br9x] (TMACBA) mixed crystals is investigated by the differential scanning calorimetry, dilatometric and dielectric methods. The phase transition is found at 363.5, 362.7, 360.5 and 350.9 K (on cooling) for TMACBA crystals with x = 0, 0.02, 0.17 and 0.42, respectively. The crystal structures of the pure bromine analogue (x = 1), TMABA, and the mixed crystal TMACBA (x = 0.55) are determined at 297 K. TMABA crystallizes in the trigonal space group Rc: a = 15.098(2) A, c = 21.906(4) A, Z = 3, R1 = 0.0393, wR2 = 0.0746. Its structure is built up of discrete Sb2Br93− bioctahedra and disordered trimethylammonium cation…
Structure, phase transitions and molecular motions in ferroelastic (C4H8NH2)SbCl6·(C4H8NH2)Cl
2002
The crystal structure at 293 K of the new pyrrolidinium chloroantimonate (V) analogue, (C4H8NH2)SbCl6(C4H8NH2)Cl, has been determined by x-ray diffraction as monoclinic, space group P21/c, Z = 8. The crystal is built up of isolated SbCl6- anions, two types of inequivalent pyrrolidinium cation and isolated Cl- ions. It undergoes five solid-solid phase transitions: at 351/374 K of first-order type (cooling/heating, respectively), at 356 and 152 K second order and at 135/141 and 105/134 K first order, detected by differential scanning calorimetry, dilatometric and dielectric measurements. The ferroelastic domain structure appears between 152 and 135 K. The proton nuclear magnetic resonance sec…
Effect of Hydrostatic Pressure on the Phase Transitions of {N(CH3)4}2ZnCl4-xBrxMixed Crystals
1991
Single crystals of the solid solution system {N(CH 3 ) 4 } 2 ZnCl 4- x Br x have been prepared in a low x region, and the effect of hydrostatic pressure on the phase transitions were measured for x =0.2 and 0.3. The normal-to-incommensurate phase transition temperatures increase linearly with increasing pressure with the rates of 0.126 K/MPa and 0.129 K/MPa for x =0.2 and 0.3 crystals, respectively. The ferroelectric III phase disappears at about 60 MPa for x =0.2 crystal. On the other hand, phase III is not observed for the x =0.3 crystal both at 0 pressure and at high pressures. The II-IV or III-IV transition temperatures also increases with increasing pressure with the rates of 0.162 K/M…
Crystal Field Excitations in CeAgl−xInx Compounds
1982
The substitution of the monovalent Ag for the trivalent In in LaAgl−xInx and CeAgl−xInx offers the possibility of influencing the conduction electron system in these compounds. The strong dependence of the spin susceptibility of La-systems on the In-concentration1 was interpreted by band calculations which suggest that the Fermi level is pushed into a region of a high 5d-eg-band density of states2. Furthermore, CeAgl−xInx is one of the rare 4f systems where a structural phase transition (from cubic to tetragonal) occurs prior to magnetic ordering. The ferromagnetic Curie temperature TC is roughly independent of x whereas the structural transition temperature Ts rises from 15 K for CeAg to a…
Morphotropic ceramic solid solutions of the Pb(B3+½Nb½)O3- PbTiO3binary system
2000
Abstract The structure, dielectric, ferroelectric and electromechanical properties of lead lutecium niobate-titanate (PLuNT) and lead erbium niobate-titanate (PErNT) binary systems are reported. The data of phase diagram, crystallographic symmetry and morphotropic phase boundaries (MPB) are provided. High values of the electromechanical coupling coefficients kp = 0.66, kt = 0.48, k31 = 0.36 of (1−x)PLuN − xPT ceramics are attained in compositions near the MPB at x≈0.41.
Structure and Magnetic Properties of the Ferromagnetic Cu3Cl126- Trimer in [(NH3C2H4)3NH]2Cu3Cl14
2004
The crystal structure consists of a strongly hydrogen bonded network of tris(N-ethylammonium)ammonium cations, Cu3Cl12(6)- trimeric species, and Cl- anions. The Cu3Cl12(6)- trimers are formed by two distorted tetrahedral CuCl4(2)- anions linked to a central square planar CuCl4(2)- anion via semicoordinate Cu-Cl...Cu mu1 bridges. The central copper ion shows only small deviations from ideal D4h symmetry, while the terminal copper ions show a mild distortion from D2d symmetry with an average trans Cl-Cu-Cl angle of 136.0 degrees. The semicoordinate linkages provide a ferromagnetic exchange pathway between the copper ions with J/k = 6.91(3) K. Short Cl...Cl contacts (3.67-3.90 angstoms) lead t…
A self-assembled tetrameric water cluster stabilized by the hexachlororhenate(IV) anion and diprotonated 2,2′-biimidazole: X-ray structure and magnet…
2008
A self-assembled tetrameric water cluster stabilized by [ReCl6]2− anions and [H4biim]2+ cations occurs in the new compound [H4biim][ReCl6]·4H2O, which exhibits a weak ferromagnetic coupling between the Re(IV) centers through an unusual ReIV–Cl⋯(H2O)⋯Cl–ReIV pathway.
Stoichiometry of LiNiO2 Studied by Mössbauer Spectroscopy
2002
From the 61Ni and 57Fe Mossbauer spectroscopy data follows the cationic site assignment in Li1−x Ni1+x O2. Our data explain the ferromagnetic properties of this material because of the appearance of Ni2+ (S = 1) among Ni3+ (S = 1/2) in Ni3+O2 hexagonal planes. We have no evidence for the ferromagnetic interaction between the NiO2 layers through the excess Ni2+ ions substituting the Li+ ions. The presence of Ni2+ found in the Ni3+O2 planes explains the absence of the Jahn-Teller distortions probably because of the electronic transfer between the Ni3+ and Ni2+ ions.