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With supersaturated carbon atoms ordering in the preferential octahedral sites of α-Fe lattice, the martensite formed in medium and high carbon steels exhibit a unique structural feature, tetragonality. In this letter, we reported anomalous nontetragonality of martensite in carbon steels by deforming quenched martensite, indicating that the disordering of interstitial carbon atoms in α-Fe lattice occurs under mechanical deformation. This order-disorder transition of interstitial carbon atoms in carbon steels provides solid experimental evidences of the prediction based on microscopic elasticity theory. [ABSTRACT FROM AUTHOR]

Exact graft copolymer (EGC) is a type of copolymer with precisely defined molecular parameters, including the number of grafts per molecule ( n), the length of the grafts ( lg), and the separation distance between the junction points (ε) in the backbone. In the present study, the phase structure of the EGC composed of poly(2-vinyl pyridine) backbone and polystyrene graft with n = 2 and n = 3 under fixed ε and lg is systematically investigated to seek a general understanding on the effect of the graft architecture on the domain spacing of the microphase-separated structure and the order-disorder transition temperature ( TODT). It is found that the TODT associated with the fluctuation-induced ODT of the EGC increases with increasing n due to the increase of the total molecular weight. Nevertheless, the domain spacing does not exhibit a monotonic change with n, as the EGC with n = 2 shows the largest domain spacing compared with that of EGC with n = 3 and the corresponding linear diblock copolymer. The experimental observation on the domain spacing is explained by a thermodynamic model considering the packing mode of the constituting chains under the junction constraint. [ABSTRACT FROM AUTHOR]

The synthesis of multicomponent perovskites ( Ln 0.25 Mn 0.75 )(Al 0.25 Ti 0.75 )O 3 ( Ln =La, Pr, Nd, Sm, Gd, Tb, Dy, Y) have been investigated using a high-pressure and high-temperature (6 GPa, 1175 °C) technique. When Ln 3+ is larger La 3+ , Pr 3+ , Nd 3+ , the A-site ordered perovskites, Ln Mn 3 (Al 0.25 Ti 0.75 ) 4 O 12 in Im -3, have been successfully synthesized. The A-site partially disordered one, (Sm 0.80 Mn 0.20 )(Sm 0.07 Mn 0.93 ) 3 (Al 0.25 Ti 0.75 ) 4 O 12 is also obtained. In the case of smaller Gd 3+ , Tb 3+ , Dy 3+ , we have obtained no single phase but two decomposed perovskite phases. When Ln 3+ is much smaller Y 3+ , it is crystallized as an A-site disorder one in Pnma . The Rietveld structural refinements of the A-site ordered and partially disordered perovskites indicate that the tilting of (Al/Ti)O 6 octahedrons for the A-site ions ordering is correlated with the (Al/Ti)–O and Ln –O bond lengths to optimize the coordination of the A - and A′ -sites. The phase stability of the A-site ordered perovskites is discussed from the viewpoint of this correlation. [ABSTRACT FROM AUTHOR]

Phase equilibria at 800, 900 and 1000 °C, as well as order–disorder and magnetic transitions of Heusler-type ordered phase were investigated in the Co–Mn–Ga ternary system. The β phase with bcc structure including the Heusler-type ordered phase exists in a wide composition range of the ternary system. It was confirmed by STEM–HAADF observation that the crystal structure of the Heusler-type ordered alloy Mn 2 CoGa is L 2 1b -type Fm 3 ¯ m (i.e., (Mn,Co) 2 MnGa), but not inverse-Heusler (Hg 2 CuTi) type F 4 ¯ 3 m . The L 2 1 / B 2 order–disorder transition temperature shows a maximum at the stoichiometric composition of Co 2 MnGa and the Curie temperature of the L 2 1 phase decreases with increasing Ga content. Magnetic moments converted from magnetization curves at 4.2 K for Co x Mn (76− x ) Ga 24 alloys well follow the generalized Slater–Pauling rule in the composition of 25 ⩽ x ⩽ 50, and magnetization curves indicate very small high-field magnetic susceptibility. [ABSTRACT FROM AUTHOR]

The reaction of the proton-transfer compound piperazine-1,4-diium pyrazine-2,3-dicarboxylate 4.5-hydrate, C4H12N22+·C6H2N2O42−·4.5H2O or (pipzH2)(pyzdc)·4.5H2O (pyzdcH2 is pyrazine-2,3-dicarboxylic acid and pipz is piperazine), (I), with Zn(NO3)2·6H2O and CoCl2·6H2O results in the formation of bis(piperazine-1,4-diium) bis(μ-pyrazine-2,3-dicarboxylato)-κ3 N1, O2: O3;κ3 O3: N1, O2-bis[aqua(pyrazine-2,3-dicarboxylato-κ2 N1, O2)zinc(II)] decahydrate, (C4H12N2)2[Zn2(C6H2N2O4)4(H2O)2]·10H2O or (pipzH2)2[Zn(pyzdc)2(H2O)]2·10H2O, (II), and catena-poly[piperazine-1,4-diium [cobalt(II)-bis(μ-pyrazine-2,3-dicarboxylato)-κ3 N1, O2: O3;κ3 O3: N1, O2] hexahydrate], {(C4H12N2)[Co(C6H2N2O4)2]·6H2O} n or {(pipzH2)[Co(pyzdc)2]·6H2O} n, (III), respectively. In (I), pyzdcH2 is doubly deprotonated on reaction with piperazine as a base. Compound (II) crystallizes as a dimer, whereas compound (III) exists as a one-dimensional coordination polymer. In (II), two pyzdc2− groups chelate to each of the two ZnII atoms through a ring N atom and an O atom of the 2-carboxylate group. In one ligand, the adjacent 3-carboxylate group bridges to a neighbouring metal atom. A water molecule ligates in the sixth coordination site. The structure of (II) can be described as a commensurate superlattice due to an ordering in the hydrogen-bonded network. In (III), no water is coordinated to the metal atom and the coordination sphere is comprised of two N, O-chelates plus two bridging O atoms. A large number of hydrogen bonds are observed in all three compounds. These interactions, as well as π-π and C=O...π stacking interactions, play important structural roles. [ABSTRACT FROM AUTHOR]

Highlights: [•] The order–disorder transition temperature for Na(BH4)1−x Cl x and Na(11BD4)1−x Cl x is highly dependent on the Cl-content, x. [•] The transition is characterized by DSC for Na(11BD4)1−x Cl x for x =0, 0.10 and 0.15. [•] No transition is observed for x ⩾0.20 on cooling to 8K. [•] The crystal structures are reported for Na11BD4 at room temperature and 8K and Na(11BD4)1−x Cl x (x =0.10, 0.15, 0.20 and 0.25) at 8K from powder neutron diffraction. [ABSTRACT FROM AUTHOR]

The superlattice structure (phase III) of {N(CH3)4}2MnCl4was analyzed from the X-ray diffraction data by using Fourier synthesis method based on maximum entropy algorithm. The partially disordered MnCl4was found without assuming a specified structural model. As the occupation probability of Cl changes, the mean position of the atom deviates continuously from thec-glide plane, which explains the temperature dependence of the superlattice reflection intensity with decreasing temperature in the commensurate phase III. The ordering of N(CH3)4is also found to be similar with the behavior of MnCl4. [ABSTRACT FROM AUTHOR]

The excess surface Gibbs energy and surface tension of pure liquid metals (originating from bcc, fcc, and hcp solid metals) of ordered and disordered surface structures are compared in this paper. It is shown that at a special temperature T an order-disorder surface phase transition is expected in all liquid metals from a low-temperature ordered surface state to a high-temperature disordered surface state. This surface phase transition is similar to the first-order bulk solid-liquid phase transition (melting). The values of T appear in the temperature interval between the melting point and the critical point of metals. Critical temperatures of metals are estimated from the equation for high-temperature disordered surfaces. [ABSTRACT FROM AUTHOR]

Abstract: Oxygen ion conduction in the Aurivillius phases Bi2Sr2(Nb or Ta)2(Ga or Al)O11.5 has been evaluated in detail. High-temperature X-ray diffraction studies, coupled with differential scanning calorimetry, electron microscopy, and conductivity measurements were used to clearly demonstrate that Bi2Sr2(Nb x Ta1−x )2(Ga y Al1−y )O11.5 with x =0, 1 and y =0, 0.5, and 1 form only multiphase specimens. The origin of the previously observed fast ion conduction is a result of interconnected Bi2O3 grains that undergo a high-temperature phase transformation to the δ-Bi2O3 polymorph. The Aurivillius phase component of the multiphase specimens does not demonstrate any type of order–disorder transformation, however, the phase transformations of the Bi2O3 are clearly observed using high-temperature diffraction and calorimetry. [Copyright &y& Elsevier]

The title compound crystallizes in the space group P21/c with the following unit cell dimensions: a=7.885(2) Å, b=25.937(2) Å, c=11.059(5) Å, β=91.067(2)°, Z=4. The examination of the structure shows a layer arrangement perpendicular to the b axis: planes of β phenylethylammonium cations [C6H5(CH2)2NH3]2+ alternate with planes of [Cd0.75Hg0.25Br4]2- tetrahedra. The cohesion of the atomic arrangement is ensured by hydrogen bonding (N&z.sbnd;H…Br) and Van der Waals contacts. DSC and Raman spectroscopy measurements were carried out and reveals a transition at T=347 K. This transition display an order–disorder mechanism involving mainly conformational changes of the organic chain [C6H5(CH2)2NH3]2+ coupled with distortion of the (Cd/Hg)Br4 tetrahedra. The transitional behavior and the crystal dynamics will be discussed and compared with those found in the literature for homologous compounds. [Copyright &y& Elsevier]

Cu2MnSnS4 shares several promising properties with the widely investigated Cu2ZnSnS4 for photovoltaic applications such as containing only earth abundant and non‐toxic elements, and suitable absorption characteristics for absorber materials. Thin film Cu2MnSnS4 samples with various cation compositions are co‐sputtered reactively followed by a high temperature anneal. Formation of Cu2MnSnS4 and co‐existence of several secondary phases is verified by XRD and Raman. Our investigation of the crystal structure based on first‐principles DFT confirms that stannite crystal structure is preferred over kesterite, although, further verification considering cation disorder is needed. The direct band gap of Cu2MnSnS4 is calculated as 1.52 eV (1.62 eV) for stannite (kesterite), which coincides with the range of the measured band gaps from spectrophotometry of 1.42–1.59 eV. After further annealing treatments below 240 °C, the absorption shows reversible changes: the band gap blue‐shifts and the Urbach tail energy is reduced. It is concluded that, just like Cu2ZnSnS4, disorder also occurs in Cu2MnSnS4. The implications of our findings are discussed and related to the current understanding of cation disorder in Cu2ZnSnS4 and related compounds. Furthermore, for the first time first‐principles DFT investigations are presented for the thiospinel Cu2MnSn3S8 which is observed experimentally as a secondary phase in Sn‐rich Cu2MnSnS4 thin films. [ABSTRACT FROM AUTHOR]

Bulk samples of kesterite (Cu2ZnSnS4, CZTS) were produced by cold-pressing and sintering of CZTS powders obtained via reactive ball-milling. An increase in the Seebeck coefficient of more than 100 μV/K, almost doubling the expected value, is noticed around a temperature of 260 °C. As pointed out by thermal analyses, this is due to a second order transition of kesterite from an ordered I-4 to a disordered I-42m crystal structure. Conversely to what happens for solar cell materials, where the transition is considered to be detrimental for the performance, it appears to be beneficial for the thermoelectric Seebeck coefficient, suggesting that higher crystal symmetry and cation-disorder due to the transition lead to thermopower enhancement. [ABSTRACT FROM AUTHOR]