Showing papers on "Orthorhombic crystal system published in 1996"
TL;DR: In this article, the results of an investigation into the grain-size dependence of lattice structure for barium titanate (BaTiO) ceramics prepared by a sol-gel method were reported.
Abstract: We report the results of an investigation into the grain-size dependence of lattice structure for barium titanate (${\mathrm{BaTiO}}_{3}$) ceramics prepared by a sol-gel method. Raman and infrared spectroscopy, x-ray diffraction, and differential scanning calorimetry were used in combination with electron microscopy to study the evolution of lattice structure and phase transformation behavior with heat treatment and grain growth from the nano scale to the micron scale for ${\mathrm{BaTiO}}_{3}$ polycrystals. Raman spectroscopy and optical second-harmonic-generation measurements indicated the onset of local room-temperature acentric crystal symmetry with heat treatment and crystallite growth, well before the observation of any tetragonal structure by x-ray diffraction. Analysis of the room-temperature Raman spectra for ultrafine grain (grain size 0.1 \ensuremath{\mu}m) polycrystals suggested that a locally orthorhombic structure preceded the globally tetragonal form with grain growth. In support of this observation, differential scanning calorimetry suggested the orthorhombic-tetragonal phase transformation shifts up through room temperature with decreasing grain size. Hot-stage transmission electron microscopy studies revealed that fine grain (grain size \ensuremath{\approxeq}0.1 \ensuremath{\mu}m) ceramics, which showed a thermal anomaly associated with the cubic-tetragonal phase transformation, were untwinned at room temperature, as well as on cycling through the normal Curie temperature, suggesting a single-domain state for individual grains. The findings are discussed in light of a number of possible causes, including the presence of processing-related hydroxyl defects and the effect of elastic constraints on phase transformation behavior for ${\mathrm{BaTiO}}_{3}$ grains in a polycrystalline microstructure. \textcopyright{} 1996 The American Physical Society.
814 citations
IBM1
TL;DR: In this paper, single crystals of the organic-inorganic layered perovskites (C4H9NH3)2MI4 (M = Ge, Sn, Pb) have been grown from aqueous hydriodic acid solutions.
Abstract: Single crystals of the organic-inorganic layered perovskites (C4H9NH3)2MI4 (M = Ge, Sn, Pb) have been grown from aqueous hydriodic acid solutions. X-ray diffraction, thermal analysis, and photoluminescence spectroscopy were used to compare crystal structure, metal atom lone-pair stereoactivity, and physical properties as a function of group IVB element. The orthorhombic (C4H9NH3)2GeI4 structure, refined in the space group Pcmn, consists of single-layer-thick perovskite sheets of distorted corner-sharing GeI6 octahedra separated by n-butylammonium cation bilayers. (C4H9NH3)2SnI4 and (C4H9NH3)2PbI4 are structurally very similar but adopt the space group Pbca, with a more ideal octahedral iodine coordination around the divalent group IVB atoms. Within the more general tin(II)-based family, (C4H9NH3)2(CH3NH3)n-1SnnI3n+1, a structural comparison between the title semiconducting n = 1 compound and the previously reported semimetallic n = 3 and metallic n → ∞ members demonstrates a correlation between perovskite...
471 citations
TL;DR: In this paper, the limits of rhombohedral and orthorhombic solid solutions were determined, as well as the evolution of their lattice parameters as a function of composition and temperature.
Abstract: The study of the Na0.5Bi0.5TiO3–K0.5Bio0.5TiO3 (NBT-KBT) system was carried out using X-ray diffraction and dielectric measurements. The limits of rhombohedral and orthorhombic solid solutions were determined, as well as the evolution of their lattice parameters as a function of composition and temperature. Dielectric permittivity measurements in a wide frequency range between 20 and 800°C showed that all materials are ferroelectric at room temperature and exhibit a diffuse, probably second-order phase transition from the ferroelectric to the paraelectric state. Several peculiar compositions showed the best piezoelectric characteristics for this type of ceramic materials.
L'etude du systeme Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 (NBT-KBT) a ete realisee par diffraction X et mesures dielectriques. Les limites des solutions solides de symetrie rhomboedrique et orthorhombique ainsi que les evolutions des parametres de maille en fonction de la composition et de la temperature ont ete determinees. Les mesures de permittivite dielectrique effectuees dans une large gamme de frequence entre 20 et 800°C ont montre que tous ces materiaux sont ferroelectriques a la temperature ambiante. Ils presentent une transition de phase diffuse, probablement du deuxieme ordre de l'etat ferroelectrique vers l'etat paraelectrique. Quelques compositions particulieres presentent des caracteristiques piezoelectriques dignes d'interět.
208 citations
TL;DR: Two novel tridentate dinucleating ligands containing benzimidazole were prepared and the interpretation of these data, including multiple scattering calculations, together with UV-vis titrations, shows that the complexes have the same structure in the crystalline state as well as in methanolic solution.
Abstract: Two novel tridentate dinucleating ligands containing benzimidazole were prepared, 1,3-bis(2-benzimidazolyl)-2-propanol (Hbbp, 1) and 1,5-bis(2-benzimidazolyl)-3-pentanol (Hbbpen, 2). Their complexing properties toward copper were studied in order to obtain structural and functional models for catechol oxidases. Syntheses and crystal structures of dinuclear Cu(II) complexes derived from these ligands are reported. [Cu2bbp2](ClO4)2·2MeOH, 3, crystallizes in the triclinic space group P1 with the following unit cell parameters: a = 7.702(3) A, b = 10.973(6) A, c = 12.396(6) A, α = 100.59(4)°, β = 99.02(4)°, γ = 98.90(4)°, V = 998.7(8) A3, and Z = 1. [Cu2bbpen2](ClO4)2·3MeOH, 4, crystallizes in the orthorhombic space group Pccn, with the following unit cell parameters: a = 17.478(9) A, b = 18.795(8) A, c = 13.888(6) A, V = 4562.2(4) A3, and Z = 4. Magnetic susceptibility measurements in the temperature ranges 4.6−459 K (3) and 4.6−425 K (4) indicate an antiferromagnetic coupling between the Cu(II) centers o...
181 citations
TL;DR: In this article, high-temperature powder x-ray diffraction data is presented for perovskite between 293 and 1523 K. The temperature-dependence of superlattice intensities and cell parameters suggests a sequence of phase transitions from the room temperature orthorhombic (Pbnm) structure to a tetragonal (I4/mcm) polymorph at temperatures in the range 1373 - 1423 K, followed by transformation to the cubic aristotype at.
Abstract: High-temperature powder x-ray diffraction data are presented for perovskite between 293 and 1523 K. The temperature-dependence of superlattice intensities and cell parameters suggests a sequence of phase transitions from the room temperature orthorhombic (Pbnm) structure to a tetragonal (I4/mcm) polymorph at temperatures in the range 1373 - 1423 K, followed by transformation to the cubic aristotype at . The intensity of the diffuse background increases on transformation to the cubic structure and is associated with disorder (and anionic mobility) of the oxygen sub-lattice. The I4/mcm - Pbnm transition induces a large spontaneous strain, but the tetragonal spontaneous strain in the I4/mcm phase due to the - I4/mcm transition is small, below the resolution of this experiment. These results add weight to suggestions from recent computer simulations that orthorhombic may transform to a tetragonal (rather than a cubic) polymorph under the conditions of the Earth's mantle, in which case the effects on electrical conductivity would not be expected to be as great as for a transition to a cubic polymorph, although the consequences for elastic properties may be more significant.
160 citations
TL;DR: In this article, structural changes in the orthorhombic-tohexagonal phase transition of polyethylene crystal have been investigated by measuring the differential scanning calorimetry, X-ray diffraction, and infrared and Raman spectra for the geometrically-constrained ultradrawn samples in the course of heating up to the melting temperature.
Abstract: Structural changes in the orthorhombic-to-hexagonal phase transition of polyethylene crystal has been investigated by measuring the differential scanning calorimetry, X-ray diffraction, and infrared and Raman spectra for the geometrically-constrained ultradrawn samples in the course of heating up to the melting temperature. The infrared and Raman spectral patterns characteristic of the hexagonal phase have been confirmed. In particular, the bands characteristic of the disordered short trans segments (shorter than five CH2 units) and the bands of the kink or double gauche linkages have been detected definitely. The degree of orientation of the averaged chain axis, as detected from the temperature dependence of the X-ray fiber diagram, was reserved well enough even in the hexagonal phase, while the orientational degree of the methylene units, as detected from the polarized infrared spectral measurement, was found to be lowered appreciably. This finding, combined with the observation of the trans and gauche ...
159 citations
TL;DR: It is proposed that the approximately 3:1 ratio between MnIIIand MnIVatoms in LaMnO3.15 gives rise to a frustrated system with largely spin glass behaviour.
144 citations
TL;DR: A series of perovskite compounds, namely, Sr 1− x Mg x TiO 3 (M = Ca, Mg; 0 ≤ x ≤ 1), has been synthesized by solid-state reaction, and characterized by Fourier transform infrared spectroscopy, Raman scattering, and X-ray diffraction.
128 citations
TL;DR: Calculations on BaIn(2) and CaPtSn show that the four-connected nets are increasingly stabilized as the valence electron count is increased from 16 to 30 valence electrons per 4 formula units, and find an interesting and understandable angular asymmetry of the tetrahedral sites in these ternary compounds.
Abstract: The crystallochemistry of and the bonding in the orthorhombic four-connected nets of BaIn2 (CeCu2 structure) and of CaPtSn (TiNiSi structure, a derivative of the CeCu2 structure) are analyzed with approximate molecular orbital calculations. Following the Zintl concept, in BaIn2 the In- ions are isoelectronic with group IV tin and should adopt a four-connected structure. In contrast to α-tin, which has a cubic diamond structure, the indium ions in BaIn2 build up an orthorhombic three-dimensional four-connected net containing distorted tetrahedra and ladder polymers of four-membered rings. In the CeCu2 structure (space group Imma) two bond angles in these distorted tetrahedra are fixed at 90°. The four-connected net in the CeCu2 structure is topologically related to the layers in black phosphorus (space group Cmca). In CaPtSn (TiNiSi structure) the orthorhombic four-connected net is formed by (PtSn)2- ions in an ordered arrangement. Calculations on BaIn2 and CaPtSn show that the four-connected nets are incr...
120 citations
TL;DR: In this article, the synthesis, crystal structure, and properties of [MnII(MCPA)2(H2O)2]n (MCPA = 2-methyl-4-chlorophenoxyacetic acid), a 2-D manganese carboxylato polymer is reported.
Abstract: The synthesis, crystal structure, and properties of [MnII(MCPA)2(H2O)2]n (MCPA = 2-methyl-4-chlorophenoxyacetic acid), 1, a 2-D manganese carboxylato polymer is reported. The synthesis of 1 has been achieved via the reaction of MCPA with MnCl2·2H2O and NaHCO3 in methanol. Crystal structure data: [C18H20Cl2O8Mn]; orthorhombic; space group Pbca; a = 7.811(6) A; b = 34.67(3) A; c = 7.481(6) A; Z = 4. The compound has a two-dimensional structure with Mn2+ atoms in an octahedral environment and mixed water/carboxylate coordination. The metal atoms are segregated in planes which are perpendicular to the b axis and are spaced 17.73 A apart. Variable-temperature magnetic susceptibility measurements indicate the presence of antiferromagnetic behavior. The EPR spectra of polycrystalline samples at 4 K show that the intensity of the signal decreases significantly with decreasing temperature and below ∼4 K becomes EPR silent.
117 citations
TL;DR: In this article, the surface adsorptive and lattice oxygen govern the sensing properties of LaFeO3 and CaxLa1−x FeO3 ceramics, and partial substitution of La3+ with Ca2+ can enhance the sensitivity of the materials to reducing gases.
Abstract: LaFEO3 and CaxLa1−xFeO3 ceramic powders have been prepared by the coprecipitation method from La(NO3)3, Fe(NO3)3 and Ca(NO3)2 aqueous solutions. The orthorhombic perovskite phases of LaFeO3 and CaxLa1−xFeO3 are characterized by X-ray diffraction patterns. The sensors fabricated with those powders have high sensitivity to alcohol. Partial substitution of La3+ in LaFeO3 with Ca2+ can enhance the sensitivity of the materials to reducing gases. The resistance of an LaFeO3 sensor in air, vacuum and alcohol-containing air has been measured. Complex impedance spectroscopy has been used to try and analyse the gas-sensing mechanism. According to the experimental results, it can be deduced that the surface adsorptive and lattice oxygen govern the sensing properties of LaFeO3 and CaxLa1−xFeO3 ceramics.
TL;DR: In this paper, a new compound with the chemical formula Th4(PO4)4P2O7, derived from the crystal structure determination, has been obtained and the unit cell parameters were obtained from powder and single-crystal X-ray diffraction data.
Abstract: The chemistry of thorium phosphate reported in the literature has been found to be erroneous. It was reconsidered in terms of careful chemical preparations and specific analytical methods. Special attention has been paid to the atom ratio value referred to r = thorium/phosphorus, which was experimentally fixed in order to obtain the correct composition of the final compound. A new compound with the chemical formula Th4(PO4)4P2O7, derived from the crystal structure determination, has been obtained. The unit cell parameters were obtained from powder and single-crystal X-ray diffraction data. It is orthorhombic (space group Pcam, Z = 2) with the cell dimensions a = 12.8646(9) A, b = 10.4374(8) A, c = 7.0676(5) A, and V = 949.00(9) A3. The atomic positions were derived from Patterson and Fourier methods and the structure was refined to an R value of 0.039. The structure consists of layers parallel to (010) containing both PO4 and P2O7 groups. These layers alternate with planes of Th atoms. The coordination sp...
TL;DR: The crystal structure and magnetic properties of the molecular-based ferrimagnet N(n-C5H11)4MnIIFeIII(C2O4)3 have been determined as mentioned in this paper.
Abstract: The crystal structure and magnetic properties of the molecular-based ferrimagnet N(n-C5H11)4MnIIFeIII(C2O4)3 have been determined. The compound is orthorhombic, space group C2221, a= 9.707(3), b= 16.140(3), c= 19.883(7)A(120 K), Z= 4[R 0.047 for I > 2σ(I)]. The structure consists of hexagonal layers of alternating MnII and FeIII bridged by C2O42–, separated by layers containing only N(n-C5H11)4+ with the alkyl chains extended, though with the terminal bonds twisted towards the gauche conformation. The terminal CH3 are embedded in the hexagonal pockets formed by three C2O42–. Since both metal ions have 3d5 configuration with 6A1 ground states the magnetic properties in the paramagnetic region mimic those of a two-dimensional antiferromagnet. Below TN= 27 K an uncompensated moment estimated as 8.78 × 10–5µB atom–1 arises, the direction of which was identified as parallel to the c axis by single-crystal magnetization measurements.
TL;DR: In this paper, the melting and crystallization behaviors under high pressure were investigated as a function of temperature and pressure, in which the triple point (orthorhombic, hexagonal and melt) exists at 320 MPa and 300°C.
TL;DR: The lattice parameters and diffraction peak profiles for KOD-doped D2O ice both in its low-temperature ordered state (ice XI) and as a function of temperature through the transition to ice Ih at 76 K were presented in this article.
Abstract: The lattice parameters and diffraction peak profiles are presented for KOD‐doped D2O ice both in its low‐temperature ordered state (ice XI) and as a function of temperature through the transition to ice Ih at 76 K. They are compared with parallel measurements on pure D2O ice. We demonstrate that ice XI is orthorhombic, with lattice parameters a=4.465(3) A, b=7.859(4) A, and c=7.292(2) A at 5 K, as compared with a=4.4974(1) A and c=7.3236(1) A for pure ice. The detransformed phase measured at 5 K has a different c‐lattice parameter from that of pure ice, with a=4.4971(1) A and c=7.3182(1) A. The transformed sample is an intimate mixture of the orthorhombic transformed phase and hexagonal untransformed ice, giving rise to elastic strain effects such that the c‐lattice parameter of the untransformed phase is shifted, giving a=4.499(1) A and c=7.311(1) A. These strain effects also produce broadening of the diffraction peaks for the transformed phase relative to those of the detransformed and pure phases. We d...
TL;DR: In this paper, the synthesis and crystal structures of BaMoO 3 SeO 3 and BaMo 2 O 5 (SeO 3 ) 2 are reported, where the MoO 6 octahedra in BaMo2 O 5(SeO3 ) 2 display a typical two short + two intermediate + two long Mo-O bond-distance distribution.
TL;DR: Mentzen et al. as mentioned in this paper solved the crystal structure of H-ZSM-5 loaded with 3.68 naphthalene per unit cell by single crystal X-ray diffraction.
TL;DR: In this article, the synthesis and structures of two key members, (18C6)K][Cd(SCN)3] (1) and (2) of a new inorganic polymers with organic spacers (IPOS) series with the general formula [H−G][M−L], were reported.
Abstract: This paper reports the synthesis and structures of two key members, [(18C6)K][Cd(SCN)3] (1) and [(18C6)2Na2(H2O)2]1/2[Cd(SCN)3] (2), of a new inorganic polymers with organic spacers (IPOS) series with the general formula [H−G][M−L], where the organic cation [H−G]q+ is a host (H)−guest (G) complex such as [(crown ether)−(alkali metal)]+ and the inorganic anion [M−L]q- is a metal (M)−ligand (L) coordination polymer such as [Cd(SCN)3-]∞. 1 and 2 were prepared from 18C6, MSCN, and CdSO4 where M = K+ (for 1) and Na+ (for 2), respectively. 1 crystallizes in an orthorhombic unit cell of Cmc21 space group symmetry with lattice parameters a = 14.734(3) A, b = 15.304(2) A, c = 10.625(3) A; V = 2396(1) A3, and Z = 4. The structure was refined to R1 = 2.3% for 878 independent reflections (2θ ≤ 46°) with I > 3σ. 2 crystallizes in a monoclinic unit cell of P21/n space group symmetry with lattice parameters a = 10.277(3) A, b = 10.915(5) A, c = 22.596(7) A, β = 111.48(5)°; V = 2359(5) A3, and Z = 4. The structure was re...
TL;DR: The crystal structure of the stable crystalline form of syndiotactic polypropylene (s-PP) was taken, only as a first approximation, as body-centered orthorhombic and described in the space group.
Abstract: The crystal structure of the stable crystalline form of syndiotactic polypropylene (s-PP) may be taken, only as a first approximation, as body-centered orthorhombic and described in the space group...
TL;DR: Chain packing in the Gd phase was found to be disordered in a way that can be expressed in terms of a distribution of subcell setting angles, and support and extend those of a recent x-ray diffraction study of the 24-carbon diacyclphosphatidylcholine gel.
TL;DR: The morphology change of V2O5crystals as a result of the Mg2+insertion was studied by scanning electron microscopy as discussed by the authors, which showed the presence of Mg (at least) at the surface of intercalated V2 O5.
TL;DR: In this paper, a broad study on the properties of Ca-substituted LaCrO3 is reported, where problems in the synthesis of ca-rich samples of La1−tCatCrO 3−δ are addressed for the La-rich region.
TL;DR: In this article, four phase transitions were observed in under pressure up to 47 GPa using x-ray diffraction in a diamond anvil cell, and a cotunnite-type structure was adopted by a group IVb dioxide, which has implications for the high-pressure behavior of the homologous compounds with smaller cations.
Abstract: Four phase transitions were observed in under pressure up to 47 GPa using x-ray diffraction in a diamond anvil cell. At close to 4 GPa, rutile-structured underwent a second-order transition to an orthorhombic, -type phase. Above 7 GPa, this -type phase transformed to a cubic phase with a modified fluorite structure. A transition to an orthorhombic phase was observed at 11.4 GPa. The intensities of the diffraction lines in this orthorhombic phase indicate a displacement of the lead ions from the fcc positions occupied in the cubic phase. This orthorhombic phase has similar cell constants (a = 10.027(2) A, b = 5.246(1) A, and c = 5.116(1) A at 26 GPa) to the orthorhombic I phase of and also that of , and could be isostructural. A further transition began above 29 GPa to a cotunnite-type phase, with space group Pnam, and Z = 4, and with a = 5.443(18) A, b = 6.346(17) A, and c = 3.368(8) A at 47 GPa. The coordination number of the lead ion is 6 in the first two phases, 6 + 2 in phase III, most probably 7 in phase IV and 9 in phase V. The volume decreases observed in the three first-order transitions are 6.9, 1.4, and 7.5% at 7, 11.4, and 29 GPa, respectively. The two higher-pressure transitions were reversible, whereas the cubic phase transformed to upon decompression, and this was retained down to ambient pressure. This is the first time a cotunnite-type structure has been adopted by a group IVb dioxide, which has implications for the high-pressure behaviour of the homologous compounds with smaller cations: and .
TL;DR: In this paper, a new parameterization is defined for the quantitative description of octahedral tilting in orthorhombic and tetragonal perovskites, and an equation is derived for the dependence of polyhedral volume ratio, Va / VB, on these parameters: Va/VB = 6cos2θm cos θz − 1, where θm = (θx + θy)/2.
Abstract: A new parameterization is defined for the quantitative description of octahedral tilting in orthorhombic and tetragonal perovskites. It contains six parameters, s1, s2, s3, θx, θy and θz. s1, s2 and s3 refer to the lengths of the lines or `stalks' joining pairs of opposite octahedral vertices, and θx, θy and θz to the angles subtended by these stalks with pseudo-cubic axes x, y and z. An equation is derived for the dependence of polyhedral volume ratio, Va / VB, on these parameters: Va / VB = 6cos2θm cos θz − 1, where θm = (θx + θy)/2. To a good approximation, lengths s1, s2 and s3 do not affect Va / VB. The validity of this equation is tested by reference to the known crystal structures of 48 ternary oxide and fluoride perovskites, and its versatility demonstrated by application to the structures of some ternary palladium and platinum hydrides. The relationship of the approach to Glazer's system of nomenclature for octahedral tilting in perovskites is considered, in particular concerning the numbers of tilts operative in a given structure. A comparison is also made with the parameterization proposed for octahedral tilting and distortion in rhombohedral perovskites [Thomas & Beitollahi (1994). Acta Cryst. B50, 549–560]. Factors governing the choice of rhombohedrai or orthorhombic symmetry are discussed, with the significance of rhombohedral symmetry in obtaining ferroelectric properties brought out. Through the compilation of a table of AO12 and BO6 polyhedral volumes, the prospect is identified of predicting both the degree of octahedral tilting and the likelihood of ferroelectric behaviour for novel, hypothetical oxide compositions.
TL;DR: In this paper, the crystal structure of ζ-Fe 2 N was studied by neutron and high resolution synchrotron powder diffraction at room temperature, and the results showed that the structure was orthorhombic.
TL;DR: In this paper, two new BIMEVOX series Bi4V2 − xMxO11 − x (M = CrIII, FeIII) have been investigated by X-ray powder diffraction, thermal analysis and ionic conductivity measurements.
TL;DR: Extended three-dimensional cationic frameworks in the solid state which contain large cylindrical or rectangular channels accommodating the PF(6)(-) or BF(4)(-) counterions are revealed.
Abstract: Homoleptic copper(I) and silver(I) complexes [Mn(L-L)2n](BF4)n (M = Cu or Ag; L-L = MeECH2EMe; E = S, Se or Te) have been prepared and characterized by analysis, FAB mass spectrometry, and IR and multinuclear NMR spectroscopy (1H, 77Se, 125Te, 63Cu and 109Ag) The single-crystal X-ray structures of [Cun(MeSeCH2SeMe)2n](PF6)n (orthorhombic, P212121, a = 10879(7) A, b = 16073(7) A, c = 919(1) A, Z = 4) and [Agn(MeSeCH2SeMe)2n](BF4)n (monoclinic, P21/c, a = 14546(9) A, b = 1465(1) A, c = 30203(9) A, Z = 4) reveal extended three-dimensional cationic frameworks in the solid state which contain large cylindrical or rectangular channels accommodating the PF6- or BF4- counterions In contrast, a single-crystal X-ray structure of [Cun(MeSCH2SMe)2n](PF6)n·nMeNO2 (orthorhombic, Pbcn, a = 15506(3) A, b = 8934(2) A, c = 25859(3) A, Z = 8) shows tetrahedral Cu(I) ions coordinated to bridging dithioethers forming an cationic ribbon-like arrangement of 8-membered rings Adjacent rings are linked by the Cu atoms
TL;DR: The ternary intermetallic compounds with general formula UTX (T = Fe, Co, Ni; X = Si, Ge) were analyzed by X-ray methods and some of their physical properties examined as discussed by the authors.
TL;DR: In this article, a new distortion of the perovskite structure is described and compared to that of the manganites with GdFeO3 type structure, and the quasi absence of Jahn Teller distortion of manganese in this phase is ascribed to its metallic properties at room temperature.
TL;DR: In this article, the authors studied the low and upper stability boundaries and the structure evolution of the Nd 1+ x Ba 2− x Cu 3 O z solid solution along its single-phase field.
Abstract: We studied the low and upper stability boundaries and the structure evolution of the Nd 1+ x Ba 2− x Cu 3 O z solid solution along its single-phase field. It was found that in oxygen the limit of the solid solution extends up to Nd 1.9 Ba 1.1 Cu 3 O z at 950–1050°C while at lower and higher temperatures it becomes narrower. In nitrogen atmosphere the substitution range is much smaller and x does not exceed 0.3 at 800°C. The replacement of Ba 2+ by Nd 3+ is accompanied by decreasing both a and c lattice constants of quenched samples. At the same time in oxygen at x ≥ 0.6 ordering phenomena occur leading to the orthorhombic distortion of the tetragonal subcell. A model of the solid solution crystal structure with a B-centered unit cell and lattice parameters a = 2 a sub , b = b sub and c = 2 c sub was suggested and refined.