Neutron Powder Data Research Articles

Formation, structure and magnetism of the metastable defect fluorite phases AVO 3.5+x ( A=In, Sc)

We report the preparation and stability of ScVO 3.5+ x and the novel phase InVO 3.5+ x. A VO 3.5+ x ( A=Sc, In) defect fluorite structures are formed as metastable intermediates during the topotactic oxidation of AVO 3 bixbyites. The oxidation pathway has been studied in detail by means of thermogravimetric/differential thermal analysis and in-situ powder X-ray diffraction. The oxidation of the bixbyite phase follows a topotactic pathway at temperatures between 300 and 400 °C in air/carbon dioxide. The range of accessible oxygen stoichiometries for the AVO 3.5+ x structures following this pathway are 0.00⩽ x⩽0.22. Rietveld refinements against powder X-ray and neutron data revealed that InVO 3.54 and ScVO 3.70 crystallize in the defect fluorite structure in space group Fm-3 m (227) with a=4.9863(5) and 4.9697(3)Å, respectively with A 3+/V 4+ disorder on the (4 a) cation site. Powder neutron diffraction experiments indicate clustering of oxide defects in all samples. Bulk magnetic measurements showed the presence of V 4+ and the absence of magnetic ordering at low temperatures. Powder neutron diffraction experiments confirmed the absence of a long range ordered magnetic ground state.

Synthesis and structure determination of Co(HNCN) 2 and Ni(HNCN) 2

Well-crystallized cobalt and nickel hydrogencyanamide, Co(HNCN) 2 and Ni(HNCN) 2, were synthesized from the corresponding ammonia complexes [M(NH 3) 6] 2+ under aqueous cyanamide conditions. The X-ray and neutron powder data evidence the orthorhombic system and space group Pnnm. The cell parameters for Co(HNCN) 2 are a=6.572(1), b=8.805(2), c=3.267(1) Å, and Z=2; for the isotypic Ni(HNCN) 2, the cell parameters arrive at a=6.457(1), b=8.768(2), c=3.230(1) Å. The octahedral coordinations of the metal ions are marginally squeezed, with interatomic distances of 4×Co–N=2.134(5) Å, 2×Co–N=2.122(9) Å, and 4×Ni–N=2.133(6) Å, 2×Ni–N=2.035(11) Å. The HNCN − units appear as slightly bent (177.5(2)° for Co(HNCN) 2 and 175.7(2)° for Ni(HNCN) 2) and exhibit cyanamide shape character due to triple- and single-bond C–N distances (1.20(2) vs. 1.33(2) Å for Co(HNCN) 2 and 1.15(2) vs. 1.38(2) Å for Ni(HNCN) 2). The infrared vibration data compare well with those of the three existing alkali-metal hydrogencyanamides.

Superspace embedding of sheelite-like structures

JANA2006 is a new version of crystallographic compu-ting system JANA [1] originally developed for incom-mensurately modulated structures. During more than 20 years of development it became widely used unified system for structure analysis of periodic and aperiodic crystals with emphasis on solving difficult structures. This unifying trend is followed further in JANA2006. The main improvement of the new system consists in complete generalization of multiphase and multisource crystallographic data input. Thus the new system can combine for instanceX-ray single crystal data with neutron powder data even for samples containing several phases in different ratios. An example utilizing combination of data will be given in the presentation. The Rietveld refinement option as already implemented into JANA2000 offers the standard profile functions and anisotropic tensors for strain profile broadening. Fundamental approach to profile fitting [2] is an important new feature in JANA2006 giving more exact physical sense to profile parameters and connecting them better with the real experimental arrangement. Support for TOF data was added, too. JANA2006 will support refinement of magnetic structures. The superspace approach to handle mutually magnetic and structural modulations is under development. Charge flipping generalized for superspace [3] will be integral part of the program as an alternative solutionmethod especially useful formodulated structures. New graphical interface attempts bringing multilevel menu-driven control to more intuitive one level interface. Dynamical elements were added like updating of Fourier contour plots or powder profiles during refinement. The automatic tasks like (super)space group determination and graphical way of adding hydrogen atoms were improved.Work with simple structure is also better supported, especially creation of CIF output conforming better to current requirements of Acta Crystallographica E,C. From the technical point of view JANA2006 differs significantly of the previous versions by possibility to allocate memory dynamically (it uses FORTRAN95) and by using precompiled binaries for LINUX and MAC OS X operating systems. All JANA programs are freeware. JANA2006 is currently available in beta version by request; the first publicly available beta version is expected at the end of this year.

Nuclear and Magnetic Structures and Magnetic Properties of Co3(OH)2(SO4)2 (H2O)2. Comparison to the Mn and Ni Analogues.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Combined neutron powder and X-ray single-crystal diffraction refinement of the atomic structure and hydrogen bonding of goslarite (ZnSO4·7H2O)

AbstractThe atomic structure of synthetic, deuterated goslarite (ZnSO4·7D2O),a= 11.8176(6) Å,b= 12.0755(7) Å,c= 6.8270(4)Å, space groupP212121,Z= 4, has been refined in a combined neutron powder diffraction and X-ray single-crystal data refinement towRp1.92%,Rp1.45% andR(F2)12.66% for the neutron powder data contribution andR(F2) 8.72% for the X-ray single-crystal data contribution. Both data sets were necessary to achieve the best overall fit agreement in the Rietveld refinement and reasonable geometry within structural units. The results of this study confirm that the H-bonding scheme for goslarite is the same as that of the other epsomite group minerals. Small but significant variations of the Zn–O bond lengths can be attributed to details of the H bonds to the O atoms of the Zn octahedra. This investigation of the atomic structure and hydrogen bonding of goslarite is groundwork for future studies into phase relationships and the mechanisms of hydration and dehydration in the ZnSO4–H2O system.

Nuclear and Magnetic Structures and Magnetic Properties of Co3(OH)2(SO4)2(H2O)2. Comparison to the Mn and Ni Analogues

We report the synthesis, crystal structure derived from X-ray single crystal and neutron powder data at 300 K, infrared spectra, thermogravimetric analysis, and the magnetic properties of Co3(OH)2(SO4)2(H2O)2 and its deuterated (d6-) analogue, as well as the magnetic structure from neutron powder data of the latter as a function of temperature. The structure consists of corrugated metal-hydroxide layers with intralayer μ6-sulfate, and the layers are connected to one another by μ4-sulfate. The magnetic properties exhibit a transition from a paramagnet to a canted-antiferromagnet at 42 K and display an unusual hysteretic spontaneous magnetization with temperature. The paramagnetic region is characterized by Curie constants of ∼9.5 emu K/mol and a Weiss constant of ∼ −70 K. From the remanant magnetization, extrapolated from the linear dependence of the isothermal magnetization with field, we estimate the canting angle to be <0.2°. Refinement of the magnetic structure from data collected on two different diffractomers (D20 at ILL, Grenoble, and G4.1 at CEA, Saclay) and considering the group analysis of Bertaut's, we find the moments to lie along the c-axis with complete compensation of the moments within one layer. The temperature dependence of the moments of the two cobalt atoms also reflects the hysteresis observed in magnetization. The magnetic model is in good agreement with magnetization measurements performed on an aligned single crystal along the three orthogonal axes of the orthorhombic unit cell.

Re-examination of the hydrogarnet structure at high pressure using neutron powder diffraction and infrared spectroscopy

Time-of-flight neutron powder data and synchrotron infrared absorption spectra were collected for katoite hydrogarnet [Ca 3 Al 2 (O 4 D 4 )3] at pressures to 9.4 and 9.8 GPa, respectively. The phase transition from space group Ia3d to I4̄3d was observed in the neutron spectrum at ~7.5 GPa, as indicated by the presence of two weak reflections (730 and 530) that violate the hkl conditions (hk0, h ≠ 2n) imposed by the a-glide operation. However, attempts to refine the high-pressure structure in space group I4̄3d did not significantly improve the fit and produced a chemically unreasonable O-D bond length at the second D position. Structure refinements in Ia3d indicate that (1) the O-D bond length, corrected for the effects of thermal motion, remains essentially constant (~0.95 Å) with increasing pressure; (2) hydrogen bond lengths shorten with increasing pressure; however, the variation in O-D···O angles indicates a preferential strengthening of H bonds; and (3) the compression mechanism is characterized by bond shortening rather than bond bending. The new results are in excellent agreement with both high-pressure X-ray diffraction experiments and ab initio calculations, and illustrate the need to eliminate peak broadening in high-pressure neutron powder experiments. IR spectra collected for the same sample showed discontinuities in both O-H and O-D vibrational frequencies at ~5 GPa, suggesting that deuteration does not significantly affect the pressure of the transition. The higher pressure observed for the transition in the neutron data is probably due to lower signal-to-noise levels, which mask the weaker, symmetry-forbidden reflections at lower pressure.

High-resolution EELS study of the vacancy-doped metal/insulator system, Nd 1−xTiO 3, [formula omitted] to 0.33.

High-resolution electron energy loss spectroscopy (EELS) spectra have been obtained for several members of the vacancy-doped metal/insulator perovskite system Nd 1− x TiO 3 where NdTiO 3 ( x = 0 ) is a Mott–Hubbard insulator and Nd 2/3TiO 3 ( x = 0.33 ), a band insulator. The insulator to correlated-metal transitions occur at x ≈ 0.20 and x ≈ 0.10 . Both O K- and Ti L 2,3-edge data were obtained on the title materials and the related d 0 perovskites, CaTiO 3, SrTiO 3 and BaTiO 3. The crystal structure of Nd 0.70TiO 3 ( x = 0.30 ) was refined from powder neutron data in Cmmm which is taken as a model for the structure of Nd 2/3TiO 3 ( x = 0.33 ) as well. The L-edge spectra for Nd 1− x TiO 3 show systematic changes consistent with the valence state evolution from all Ti 3+ ( x = 0.0 ) to all Ti 4+ ( x = 0.33 ). Octahedral crystal fields of 1.5 and 2.0 eV were inferred from the L-edge data for NdTiO 3 and Nd 2/3TiO 3 by comparison with calculated spectra from the literature. Broader L 3 and L 2 peak widths for Nd 2/3TiO 3 than for the other d 0 perovskites are attributed to the more complex crystal structure of this material which includes two Nd sites with partial occupation and a more distorted Ti–O environment with low site symmetry. A markedly different O K-edge spectrum for Nd 2/3TiO 3 is attributed to the involvement of Nd 5 d levels.

Synthesis and Characterization of a Porous Magnetic Diamond Framework, Co3(HCOO)6, and Its N2 Sorption Characteristic

[Co3(HCOO)6](CH3OH)(H2O) (1), the isostructural analogue of the porous magnet of coordination framework [Mn3(HCOO)6](CH3OH)(H2O), and its desolvated form [Co3(HCOO)6] (2) were prepared and characterized by X-ray and neutron diffraction methods, IR, thermal analyses, and BET, and their magnetic properties were measured. The parent compound, 1, crystallizes in the monoclinic system, space group P21/c, a = 11.254(2) A, b = 9.832(1) A, c = 18.108(3) A, beta = 127.222(2) degrees , V = 1595.5(4) A3, Z = 4, R1 = 0.0329 at 180 K. It possesses a unit cell volume that is 9% smaller than [Mn3(HCOO)6](CH3OH)(H2O) due to the smaller radius of Co2+ ion. Compared with the parent compound 1, the desolvated compound 2 has slightly larger lattice with cell parameters of a = 11.2858(4) A, b = 9.8690(4) A, c = 18.1797(6) A, beta = 127.193(2) degrees , V = 1613.0(1) A3, R1 = 0.0356 at 180 K. The cell parameters of 2, obtained from neutron powder data at 2 K, are a = 11.309(2) A, b = 9.869(1) A, c = 18.201(3) A, beta = 127.244(8) degrees , V = 1617.3(5) A3. The pore volume reduces from 33% to 30% by replacing Mn by Co. The material exhibits a diamond framework based on Co-centered CoCo4 tetrahedral nodes, in which all metal ions have octahedral coordination geometry and all HCOO groups link the metal ions in syn-syn/anti modes. It displays thermal stability up to 270 degrees C. The compound easily loses guest molecules without loss of crystallinity, and it partly reabsorbs water from the atmosphere. Significant N2 sorption was observed for the desolvated framework suggesting that the material possesses permanent porosity. The magnetic properties show a tendency to a 3D long-range magnetic ordering, probably antiferromagnetic with a spin canting arrangement below 2 K.

3‐Dimensional Methylammonium and Ammonium Templated Lithiumberyllofluoro Frameworks.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The atomic structure of bakerite and its relationship to datolite

Four samples of bakerite, Ca4B5Si3O15(OH)5, were studied by means of IR, TG/DSC, EPMA, and X-ray and neutron diffraction. Chemical analyses can readily discriminate bakerite from datolite, Ca4B4Si4O16(OH)4, by the distinctly lower SiO2 content of the former. The Rietveld refinement of the combined neutron and X-ray powder data allow the determination of the crystal structure of bakerite to Rp 3.09%. The crystal structure can be derived from that of datolite by the substitution 0.25Si 4+ + 0.25O 2– ↔ 0.25B 3+ + 0.25(OH) – at the Si-centered tetrahedral site. This leads to the crystal chemical formula Ca4B5Si3O15(OH)5. Both of the two hydrogen positions in the bakerite structure, one with full occupancy, the other with 25% occupancy, were precisely located. The water molecule generally thought to be present in bakerite structure is actually absent. The excess water detected in chemical analyses can be attributed to the presence of minor impurities. Given the consistent composition of bakerite from various localities and no evidence for substitution of B for Si in datolite, bakerite is retained as a distinct species. A possible explanation of the peculiar 5:3 boron to silicon ratio in bakerite is provided.

3-Dimensional Methylammonium and Ammonium Templated Lithiumberyllofluoro Frameworks

Two three-dimensional lithiumberyllofluoride materials, of the same framework stoichiometry but different topologies, have been synthesized using hydrothermal pressure conditions and ammonium/methylammonium cations as structure-directing species. Compound I, [Li2Be2F7][NH4], and compound II, [Li2Be2F7][CH3NH3], both crystallize in orthorhombic space groups: Pca21 for I and Cmcm for II. Single crystal analysis reveals that the materials have slightly different 3-D framework topologies for the [Li2Be2F7] framework composed of [LiF4] and [BeF4] tetrahedra connected through doubly and triply bridging fluorides. Both networks can be viewed as sheets formed of 3- and 4-nets that link perpendicular to the sheet, through a bridging fluoride, to form six-membered interlayer pores. The six-membered channels contain the amine species hydrogen-bonded to framework fluoride ions surrounding the interior of the pore. The thermal stability, spectroscopic properties, and both powder X-ray and neutron data of these compou...

Ca2MgWO6 from neutron and X-ray powder data.

The room-temperature structure of the B-site-ordered complex perovskite dicalcium magnesium tungstate, Ca(2)MgWO(6), has been determined by simultaneous Rietveld refinement of neutron and X-ray powder diffraction patterns. Ca(2)MgWO(6) is characterized by B-site ordering and an a(-)a(-)c(+)-type BO(6) octahedral tilt mechanism.

A new octahedral tilt system in the perovskite phase Ca 3Nb 2O 8

The perovskite-related phase Ca 3Nb 2O 8, when grown as single crystals from a calcium vanadate flux, incorporates a small amount of vanadium from the flux to form the composition Ca 3Nb 2− x V x O 8 with x=0.025. The crystals have pseudo-cubic symmetry with a=6× a c(perovskite). The actual symmetry is rhombohedral, space group R3, with a h=16.910(1) Å, c h=41.500(2) Å. The structure was solved using a combination of single-crystal methods together with constrained refinements of powder X-ray and neutron powder data. The unit-cell composition is [Ca 138□ 24] A [Ca 42Nb 117V 3] B[O 480□ 6], with vacancies in both the anion sites and A-cation sites. The Ca and Nb atoms are fully ordered in the B-sites such that (001) layers containing only Nb-centered octahedra alternate with layers containing both Nb-centered and Ca-centered octahedra. At the origin B-site, ordered oxygen vacancies result in the octahedron being transformed to a tetrahedron, which, in the single crystals, is occupied by vanadium. The structure displays a new type of octahedral tilt system in which 3×3×3 blocks of ( a + a + a +) tilts are periodically twinned on the pseudo-cubic {1 0 0} c planes.

Multiple-data-set Rietveld analysis using isotopes in powder neutron diffraction. 2. Positional and anisotropic thermal displacement parameter determinations in CuO (tenorite) at 2 K and 300 K

The technique of isotope-substitution neutron diffraction (ISND) and combined-data-set Rietveld analysis from powder neutron data of crystalline materials is presented and compared with single-data-set powder refinement methods. The rationale behind improvements in the precision and accuracy of the refined model as a result of reduction in parameter correlation in the least-squares technique is described. The improvements are demonstrated practically through a study of isotopically copper-substituted tenorite, CuO, at 2 and 300 K. Typically, the estimated errors on structural parameters from the combined analysis technique are 30% lower than separate single-data-set analyses. Comparison of the precision and accuracy of the structural models obtained from this investigation with previous single-crystal X-ray studies are also presented.

Structure and ionic conductivity in doped LaGaO 3

LaGaO3 doped with lower valence cations to create vacancies in the oxygen lattice is a promising new material for technical applications due to its excellent oxygen-ionic conductivity. In order to understand the conduction mechanism and its temperature dependence, neutron powder data were collected between 2 and 1273 K on the instrument E9 at HMI (Berlin). The structures were refined in space group I2/a derived from the ideal perovskite structure by anti-phase rotations of the O6 octahedra around [100] and [011]. Strong anomalies of various parameters can be related to anomalies in the conductivity curve. Although the distortions are small and no corresponding splitting of the reflections is directly observable in the powder pattern, the profile refinement technique allows a reliable determination even of the monoclinic cell. Disorder effects are derived from an analysis of the atomic displacement parameters.

High-pressure single-crystal X-ray and powder neutron study of F,OH/OD-chondrodite: Compressibility, structure, and hydrogen bonding

The crystal structure of a natural F-bearing chondrodite [Mg4.64Fe0.28Mn0.014Ti0.023(Si1.01O4)2F1.16OH0.84; a = 4.7328(1), b = 10.2749(2), c = 7.8756(1) Å, a = 109.065(1)∞; space group P21/b (a unique)] from the Tilly Foster mine (Brewster, New York) and the structure of a deuterated synthetic analogue [Mg5(SiO4)2F1.10OD0.90] were refined at high pressure using single-crystal X-ray and time-of-flight neutron powder diffraction data, respectively. The isothermal equation of state was determined from single-crystal high-precision X-ray diffraction measurements of unit-cell parameters as a function of pressure up to 9.63(1) GPa. A third-order Birch-Murnaghan equation-of-state fit to pressurevolume data results in V0 = 362.00(2) Å3, K0,T = 117.0(4) GPa and KT' = 5.6(1). The larger value of K0,T relative to that determined for the OH end-member confirms that F makes the chondrodite structure less compressible. The axial compressibilities behave anisotropically with fitted parameters a0 = 4.73282(9) Å, K(a)0 = 458(3) GPa, and K(a)' = 28.9(9); b0 = 10.2759(3) Å, K(b)0 = 298(1) GPa, and K(b)' = 13.4(4); c0 = 7.8759(2) Å, K(c)0 = 316(2) GPa, and K(c)' = 16.7(5). X-ray structural investigations at 0.0001, 4.952(7), and 9.550(7) GPa in a diamond-anvil cell reveal a complex compression mechanism. The greatest changes with pressure occur in the M2 octahedra, which are located at the flexion points of the octahedral chain. These octahedra have the longest bonds at ambient conditions due to cation-cation repulsion, which displaces the cation from the centroid of the octahedron. The application of pressure overcomes the effect of cation-cation repulsion inducing a strong bond-length compression. The neutron powder data were collected at 0.0001, 1.26(1), 2.89(2), 3.87(1), 5.27(2), and 7.04(2) GPa in the Paris-Edinburgh cell using a new gasket design and a fluid pressure medium. Changes in the O-D···O/F hydrogen bond geometry with pressure can be interpreted in terms of a rotation of the OD vector and a reduction in the degree of static disorder associated with the hydrogen bond acceptor/donor site. These new crystallographic data are discussed in terms of corresponding spectroscopic measurements reported recently in the literature

AgCuO2—Synthesis, Crystal Structure, and Structural Relationships with CuO and AgIAgIIIO2

The new silver cuprate AgCuO2 was synthesized by applying a low-temperature route. AgCuO2 precipitates as a microcrystalline black and thermally labile powder from concentrated aqueous solutions of copper and silver nitrate under alkaline and oxidizing conditions. Using the positional parameters of AgAgO2 as a starting set, Rietveld refinements have been performed using X-ray and neutron powder data (P21/c, a=5.8657(3), b=2.8062(2), and c=6.0770(3) Å, β=108.106(4)°, Z=2, Rp=6.61%, Rwp=5.00% for joint refinement). The crystal structure consists of chains of ladder-like CuO4 rectangles running along [010], interconnected by AgO2 dumbbells. For physical and crystal chemical reasons the oxidation states +I for silver and +III for copper, respectively, have been assigned. Similar to AgAgO2 and CuO the metal cations form a fcc structure with oxygen at positions slightly displaced from the centers of the octahedral vacancies. The small differences from the AgAgO2 structure can be traced back to a different off-center position in the octahedral void.

Ferroelectric Properties and Crystal Structure of the Layered Intergrowth Phase Bi3Pb2Nb2O11Cl

The crystal structure and physical properties of Bi3Pb2Nb2O11Cl, a member of the Sillen−Aurivillius phase intergrowth family, have been probed using powder neutron diffraction, high-resolution transmission electron microscopy (HRTEM), second harmonic generation (SHG) tests, and alternating current impedance methods. It is shown that this compound undergoes a diffuse ferroelectric type phase transition at Tc ∼ 683 K. Although the powder neutron diffraction data show that the crystal structure has pseudo-tetragonal symmetry (parent space group P4/mmm, ap = 3.910 38(6) and cp = 18.8342(3) Å at 298 K), electron diffraction data clearly show a weak superlattice (ao ∼ bo ∼ (2)1/2ap, co = cp) compatible with a reduction of symmetry to orthorhombic, analogous to that observed in the related Aurivillius phases, such as SrBi2Ta2O9. Detailed analysis of the SHG data as a function of temperature suggests the existence of ordered polar nanodomains, compatible with the observation of “average” tetragonal symmetry in the neutron diffraction data. These observations, together with the presence of marked frequency dependence of Tc, point toward a relaxor type ferroelectric behavior. The nature of the crystal structure, namely, a regular intergrowth of Aurivillius-like and Sillen-like blocks, [M2O2]/[MNb2O7]/[M2O2]/[Cl] [M = Bi, Pb], has been established from both Rietveld refinement of the powder neutron data and directly from HRTEM images. The observation of ferroelectricity in this material suggests the existence of a wider family of new ferroelectrics analogous to the Aurivillius phases.

Ab Initio Determination of Bi4.86La1.14O9 Monoclinic Structure from Powder Neutron Diffraction Data. Characterization of the Related Solid Solution

This paper deals with the ab initio determination of ϵ-Bi4.86La1.14O9 monoclinic structure from powder neutron data using the Rietveld method, and with physical properties characterization of a related solid solution. ϵ-Bi4.86La1.14O9, obtained from the annealing of a quenched rhombohedral high- temperature β1 sample, is monoclinic, P2/c, a=9.4956(3) Å, b=3.9742(1) Å, c=7.0425(2) Å, β=104.700(2)°; Z=1. The structure refinement converged to RF=0.043 and RBragg=0.047. The structure is built from cationic slabs parallel to (100) faces of the monoclinic cell. Each cell corresponds to one slab containing a mixed Bi0.86La1.14 cationic layer (Bi(1)) sandwiched between two equivalent bismuth layers (Bi(2)). The cohesion of the cations in the slabs results from the presence of the oxygen atoms distributed over three sites. Six O(1) and two O(2) atoms form a slightly distorted cubical polyhedron around the mixed cationic site (Bi(1)). Bi(2) atoms are surrounded by seven oxygen atoms in a very distorted polyhedron. The important delocalization of Bi(2) lone pairs toward the interslab spaces leads to significant bonds with the adjacent slabs and to the cohesion of the structure. ϵ-Bi4.86La1.14O9 is the low symmetry variety of a particular sample of a wide solid solution domain that, formulated Bi1−xLaxO1.5, has been investigated for 0.15≤x≤0.325. The formation of this phase from the irreversible transformation of quenched-β1 on heating and the subsequent transitions ϵ→β2→β1 have been evidenced by thermodiffractometry, conductivity measurements versus temperature, dilatometry, and thermal analyses. Thermal expansion coefficients (×105) are for a, c, and/or lattice volume for a quenched-β1, ϵ, β2 or β1 variety of Bi4.86La1.14O9 (x=0.19) respectively: 1.74, −0.72, 2.78; 5.25; 1.74, 1.81, 5.37; 0.99, 1.08, 3.90. The corresponding activation energies are 0.94, 0.83, 0.84, and 0.21 eV. The ϵ→β2 transition, irreversible for 0.15≤x≤0.275, appears partly reversible for 0.3≤x≤0.325.