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Electrical conduction properties of Sr-doped PrPO4, NdPO4 and SmPO4 with the monazite structure were investigated at 500–925 °C under H2/H2O reducing conditions. From H/D isotope effects and p(H2)-dependencies of the conductivities, it was found that the materials dominantly conducted protons under the wet reducing conditions although the materials slightly showed n-type electronic conduction at higher temperatures. Based on p(H2O) and p(H2)-dependencies of the conductivities, defect structures of the materials under the reducing conditions were discussed. As a result, it was considered that major positive defects were oxygen deficits at higher temperatures and protons at lower temperatures.

The electrical conductivity of LaP 3 O 9 doped with 1 mol% of divalent metals (Ca, Sr, and Ba) substituting La has been investigated at p (H 2 O) = 0.1–5 kPa, p (O 2 ) = 0.01–100 kPa and T = 573–973 K. H/D isotope effects, proton transport number measurements, and independence of conductivity on p (O 2 ) showed that acceptor-doped LaP 3 O 9 exhibits predominantly proton conduction. The conductivity was largely independent of p (H 2 O) at constant temperature, indicating that the acceptor was charge compensated by protons and exhibited protonic conduction even at low p (H 2 O). The conductivities depended considerably on the dopant species and increased in the order Ca

Electrical conduction in 1 mol% Sr-doped (La 0.99 Ce 0.01 )PO 4 was investigated at 500–925 °C under H 2 /H 2 O and H 2 O/O 2 conditions. Conductivities of the material at the investigated temperatures were 10 − 5.1 –10 − 3.6 S·cm − 1 under the wet reducing condition, and 10 − 5.4 –10 − 3.7 S·cm − 1 under the wet oxidizing condition. H/D isotope effect on conductivity confirmed dominant protonic conduction under the both conditions. Defect structures in the material were discussed from partial pressure dependency of the conductivity. Consequently, it was suggested that Ce 4+ at Ce 3+ sites mainly compensated acceptor charge under oxidizing conditions, although the material primarily conducted protons. On the other hand, under reducing condition, protons and oxygen deficits became dominant positive defects while reducing Ce 4+ to Ce 3+ .

Electrical conduction properties of undoped and 1 mol% Sr-doped LaP3O9 glasses and glass–ceramics were investigated over the temperature range of 673–1123 K. Both the materials showed relatively low conductivities in the glassy state. However, the conductivity of the Sr-doped LaP3O9 glass significantly increased with a heat treatment above the crystallization temperature, while the conductivity of the undoped LaP3O9 glass did not improve even after the heat treatment. It was concluded that crystallization of the Sr-doped LaP3O9 glass induced protonic conduction and thus enhanced the conductivity. Electrical conduction properties of the Sr-doped LaP3O9 glass–ceramic fundamentally resembled those of the sintered crystalline Sr-doped LaP3O9.

Electrical conduction in the monazite-type LaPO 4 doped with 1 mol% of alkaline earth metals (Mg, Ca, Sr, and Ba) was investigated by using conductivity measurements under 0.4–5 kPa of p (H 2 O) and 0.01–100 kPa of p (O 2 ) at 500–925 °C. The Sr-doped LaPO 4 exhibited highest conductivities among the four samples. Conductivities of the Ca-doped LaPO 4 were in same levels as those of the Sr-doped sample, but the Ba-doped LaPO 4 showed conductivities in almost half magnitude compared with the Sr- and Ca-doped samples. Conductivities of the Mg-doped LaPO 4 were much lower than those of the other doped samples, and were comparable with those of the undoped LaPO 4 . From humidity dependence and H/D isotope effect of the conductivity, it was found that the Ca-, Sr-, and Ba-doped LaPO 4 conducted protons dominantly under moisturized conditions, whereas the Mg-doped LaPO 4 did not show significant protonic conduction. The differences in conduction properties depending on the doped alkaline earth metals could be basically interpreted by the differences in the solubility of the alkaline earth metals into LaPO 4 . The p (H 2 O) and p (O 2 ) dependencies of the conductivities of the Ca-, Sr-, and Ba-doped LaPO 4 were finally discussed in terms of defect equilibria.

( x /2)Sr 2 P 2 O 7 –(1− x )LaPO 4 ( x =0–0.60) was prepared with a solid state reaction between LaPO 4 and SrHPO 4 , and its electrical conduction was investigated by using conductivity measurements under 0.4–5 kPa of p (H 2 O) and 0.01–100 kPa of p (O 2 ) at 500–930 °C. From humidity dependence and H/D isotope effect of the conductivity, it was found that ( x /2)Sr 2 P 2 O 7 –(1− x )LaPO 4 with x >0 conducted protons dominantly under moisturized conditions, whereas LaPO 4 ( x =0) did not exhibit protonic conduction. The conductivity of ( x /2)Sr 2 P 2 O 7 –(1− x )LaPO 4 showed a maximum when x =0.02–0.03, which was nearly equal to the solubility limit of Sr into LaPO 4 . These results suggested that substitution of Sr for La was essential to induce protonic conduction in Sr 2 P 2 O 7 –LaPO 4 system and that existence of Sr 2 P 2 O 7 as a secondary phase deteriorated the conductivity. Finally, p (H 2 O) and p (O 2 ) dependencies of the conductivity were discussed in terms of defect equilibrium.

High temperature protonic conduction in 1 mol% Sr-doped (La 1− x Sm x )PO 4 ( x =0.3, 0.5 and 0.7) with the monazite structure (S. G.: P 2 1 / n ) was investigated. The conductivities of the materials under wet atmosphere were considerably higher than those under dry atmosphere. From the conductivity measurements under H 2 O- and D 2 O-containing atmospheres, it was found that the magnitude of H/D isotope effect was 1.2–1.4. These results indicated that protonic conduction was dominant in the materials under wet atmosphere. The p (H 2 O) dependencies of the conductivities were discussed in terms of the defect equilibria, and, as a result, higher Sm content in 1 mol% Sr-doped (La 1− x Sm x )PO 4 seemed more preferable for proton dissolution.

Electrical conduction in La 7 P 3 O 18 was investigated by using conductivity measurements under 0.4–5 kPa of p (H 2 O), and 0.01–100 kPa of p (O 2 ) at 500–930 °C. The conductivity of La 7 P 3 O 18 was considerably enhanced by Sr substitution for La. The Sr-doped La 7 P 3 O 18 had higher conductivities in wet than dry conditions, and exhibited the apparent H/D isotope effect on conductivity. From these results, it was found that La 7 P 3 O 18 conducted protons dominantly by substituting Sr for La and that conducting protons were introduced through equilibrium between the material and the water vapor in ambient atmosphere. Results of conductivity measurements under various p (H 2 O) and p (O 2 ) suggested that p-type electronic conduction became significant in addition to protonic conduction with increasing temperature, increasing p (O 2 ) and decreasing p (H 2 O). The conductivity behavior of Sr-doped La 7 P 3 O 18 was rather similar to that of acceptor-doped LaPO 4 , although the conductivity of Sr-doped La 7 P 3 O 18 was lower than that of acceptor-doped LaPO 4 .

Electrical conduction in lanthanum orthoborates LaBO 3 with the orthorhombic aragonite-type structure (S. G.: Pnam) was investigated by using conductivity measurements under 0.4–5 kPa of p (H 2 O) and 0.01–100 kPa of p (O 2 ) at 500–930 °C. From humidity dependence and H/D isotope effect of the conductivity, it was found that LaBO 3 exhibited dominantly protonic conduction under wet conditions by substituting Sr for La. Results of conductivity measurements under various p (H 2 O) and p (O 2 ) suggested that the contribution of electron hole conduction became significant as temperature increased, p (O 2 ) increased and p (H 2 O) decreased, although protonic conduction was estimated as predominant under the conditions used. The conductivities of the 1 mol% Sr-doped LaBO 3 were 1×10 −5 –2×10 −4 S cm −1 under moisturized conditions at 500–930 °C. The conductivity behaviors as well as the conductivity values of the Sr-doped LaBO 3 with the aragonite-type structure were quite similar to those of the acceptor-doped rare earth orthophosphates, indicating a similar proton conduction mechanism in these oxoacid salts.

Electrical conduction in undoped and Ca-doped NdBO3 with the orthorhombic aragonite-type structure was investigated by using conductivity measurements under 0.4-5kPa of p(H2O) and 0.01-100kPa of p(O2) at 500-925°C. From humidity dependence and H/D isotope effect of the conductivity, it was found that NdBO3 became a protonic conductor under wet conditions by partially substituting Ca for Nd. The conductivities of 1mol%Ca-doped NdBO3 were 10-5.4-10-4.1 S⋅cm-1 under wet condition at 500-925°C. As temperature increased, electron holes became to contribute to the conduction, although protons were estimated as dominant charge carriers under the conditions employed. The p(H2O) and p(O2) dependence of the conductivity were discussed in terms of defect equilibrium. Conductivity behaviors as well as conductivity values of Ca-doped NdBO3 were rather similar to those of the Sr-doped LaBO3 with the same crystal structure.

Electrical conduction in rare earth orthophosphates, LnPO4 (Ln=La, Pr, Nd and Sm), with the monazite structure (P21/n) was investigated by using conductivity measurements at 500–925 °C. From the conductivities of undoped and 1 mol% Sr-doped LnPO4 under wet (H2O and D2O) and dry atmospheres, it was found that LnPO4 began to conduct protons under wet atmosphere by substituting Sr for Ln. The conductivity behavior of 1 mol% Sr-doped LnPO4 versus p(H2O) and p(O2) was discussed in terms of the defect equilibria. It was concluded that protonic conduction was dominant in the materials though electron holes contributed slightly to the total conductivity as temperature increased. All the 1 mol% Sr-doped LnPO4 investigated in this study exhibited similar electrical conduction regardless of rare earth element used.

Electrical conduction in Ca-doped YPO 4 with the tetragonal xenotime-type structure was investigated by using conductivity and thermoelectric power measurements under 0.4–8 kPa of p (H 2 O) and 0.01–100 kPa of p (O 2 ) at 500–930 °C. The conductivity of the 3 mol% Ca-doped YPO 4 was 4×10 −6 to 2×10 −4 S cm −1 in moisturized conditions at 500–930 °C. From humidity dependence and H/D isotope effect of the conductivity, it was found that YPO 4 exhibited protonic conduction in moisturized conditions by substituting Ca for Y. Results of conductivity and thermoelectric power measurements versus p (H 2 O) and p (O 2 ) showed that protonic conduction in Ca-doped YPO 4 was rather dominant, and that contribution of other ions or electronic conduction to the total conductivity was regarded as negligible. The magnitude of H/D isotope effect was from 1.3 to 1.6 and the activation energy for the D 2 O-treated sample was 0.03 eV higher than that for the H 2 O-treated sample, indicating semiclassical behavior in the free proton-hopping process in the material.

The spark plasma sintering (SPS) method was employed to prepare sintered specimens of proton conducting Sr-doped LaPO4 ceramics. The relative densities of the sintered Sr-doped LaPO4 were around 99% when higher sintering temperatures than 1050°C were applied for the SPS process, while only 93% of relative density was achieved with the conventional pressure-less sintering (PLS) method at 1200°C. Electrical conduction properties of the sintered samples with the SPS method at 1200°C were evaluated by using conductivity measurements at 500-930°C under 0.4-5kPa of p(H2O) or p(D2O) and 0.01-100kPa of p(O2). The specimen prepared with the SPS method showed similar conductivities and conduction properties as that prepared with the PLS method. These results suggested that the SPS method was a useful sintering technique to prepare proton conducting phosphate-based ceramics with a high density while keeping a feature of protonic conduction.

The formation diagram of Bi-Fe-OH- system in the aqueous solution was studied using hydrothermal or "wet" method. Three kinds of bismuth-ferricoxides, Bi25FeO40 (Fe-sillenite), BiFeO3 and Bi2Fe4O9 were obtained depending on their reaction conditions. The stoichiometric Bi25FeO40 has two kinds of particle shapes, the cubic and the tetrahedral, depend on its reaction conditions, although formation mechanism of the two kinds of particle shapes is not clear yet. The precipitate obtained below 100°C from starting materials with higher ratio of Fe/Bi than 3.8mole% showed interesting feature as follows. The precipitate gave only analogous XRD spectrum of Bi25FeO40, but observations by SEM and Mossbauer effect showed the surface of the precipitate was coated homogenously with fine particles of amorphous Fe oxide. The Bi25FeO40 coated with amorphous fine particles of Fe oxide (hereafter described as pseudo Fe-sillenite) reacted with CO2 gas or CO32- in aqueous solution and easily converted to Bi2O2(CO3) at the mild reaction conditions. The gradual conversion took place even at the room temperature during the prolonged period. The phenomena may be applied to the immobilization of the CO2 in the air and in the aqueous solution.

The formation diagram of α-Bi2O3-HNO3-H2O system was studied using hydrothermal or "wet" method. Three kinds of compound of bismuth basic nitrate complex oxides were separated as single phases and determined their chemical compositions. The existence of these phases was previously found by XRD measurements, although those phases have been obtained only as mixture of multi phases precipitates. The new compounds have the chemical composition of Bi2(NO3)O2(OH)⋅7H2O, Bi2(NO3)O2(OH)⋅H2O, and Bi4(NO3)O2(OH)7, respectively. At the same reaction conditions of temperature (above 60°C) and pH in the a-Bi2O3-HNO3-H2O system and the BiONO3-KOH-H2O systems, it was affirmed that the same kind of precipitates were formed regardless of the kind of starting reagents.

Conductivities of undoped and 5mol% Sr-doped NdPO4 were investigated with the dc four-probe method at temperatures from 500 to 925°C under various p(H2O) and p(O2). The conductivity of 5 mol% Sr-doped NdPO4 was higher under wet than dry atmosphere though that of undoped NdPO4 was almost independent of p(H2O). The conductivity of 5 mol% Sr-doped NdPO4 was lower under D2O than H2O containing atmosphere. These results indicated that NdPO4 conducted protons under wet atmosphere by substituting Sr for Nd. Conductivity behavior of this material versus p(H2O) or p(O2) was discussed in terms of defect equilibrium. It was concluded that protons were dominant charge carriers at investigated temperatures though electron holes became to contribute slightly to the total conductivity with increasing temperature.

The formation diagram of α-Bi2O3-HNO3-H2O system was studied using hydrothermal or "wet" method. Three kinds of compound of bismuth basic nitrate complex oxides were separated as single phases and determined their chemical compositions. The existence of these phases was previously found by XRD measurements, although those phases have been obtained only as mixture of multi phases precipitates. The new compounds have the chemical composition of Bi2(NO3)O2(OH)⋅7H2O, Bi2(NO3)O2(OH)⋅H2O, and Bi4(NO3)O2(OH)7, respectively. At the same reaction conditions of temperature (above 60°C) and pH in the a-Bi2O3-HNO3-H2O system and the BiONO3-KOH-H2O systems, it was affirmed that the same kind of precipitates were formed regardless of the kind of starting reagents.

Protonic conduction and defect structures in Sr-doped LaPO 4 (Sr=0–7 mol%) were investigated by using conductivity, MAS-NMR spectroscopy and FT-Raman spectroscopy measurements. The results of MAS-NMR and FT-Raman spectroscopy measurements revealed that hydrogen phosphate groups, possibly hydrogen phosphate ions HPO 4 2− , and pyrophosphate ions P 2 O 7 4− existed in Sr-doped LaPO 4 under wet and dry conditions, respectively, in addition to orthophosphate ions PO 4 3− . Based on these results, we proposed a defect structure model for Sr-doped LaPO 4 . According to this model, La substitution with Sr leads to formation of P 2 O 7 4− as intrinsic positive defects, and in wet atmosphere, protons are introduced into the phosphate forming hydrogen phosphate groups through the equilibrium between P 2 O 7 4− and water vapor. The conductivity behavior of Sr-doped LaPO 4 versus water vapor and oxygen partial pressures supported this defect structure model.

A lithium-manganese spinet was synthesized by hydrothermal method in mixed lithium-alkaline aqueous solution. It was confirmed that the mixed lithium-alkaline aqueous solution dissolved with Li-salt (LiC1, Li2SO4, LiNO3) and ROH (LiOH, NaOH, KOH) was excellent reaction environment for hydrothermal synthesis. The obtained lithium-manganese spinet showed analogous electrochemical behavior to the calcined spinet.

A new low temperature processing route of lithium-manganese spinel was developed. In this process, a lithium manganese spinel was prepared by extracting Li ion from LiMnO2 compound in distilled water or in acidic solution of low H2SO4 concentration. In some reaction conditions, lithium-manganese spinel can be obtained below the temperature of 100°C in H2SO4 acid aqueous solution. The new processing route of lithium manganese spinel below 100°C throughout entire route may be easy to the environment.

The Li–Mn-spinel was synthesized using hydrothermal reaction through γ-MnOOH in 0.050∼0.150 mol/l LiOH aqueous solution at 130∼170°C. The composition of the as-precipitated Li–Mn-spinel depended on both the reaction temperature and the concentration of LiOH aqueous solution. The particle was rod-shaped and the average size was around 0.2×0.2×1 μm. The charge–discharge characteristics of the as-precipitated Li–Mn-spinel were investigated in the system of Li–Mn-spinel/EC–DEC/Li. The as-precipitated Li–Mn-spinels showed an electrochemical behavior comparable to those prepared using the conventional calcination method, and the first discharge capacity varied from 62 to 107 mAh/g depending on Li content in the spinel.

In the course of hydrothermal synthesis of lanthanum vanadates, zircon-type LaVO 4 and LaV 3 O 9 have been obtained and structurally characterized. The former is a metastable phase, and the latter is a new compound. Single-crystal X-ray diffractometry confirmed the zircon-type structure for LaVO 4 : I 4 1 / amd with a =7.4578(7) A, c =6.5417(9) A, and Z =4; R =0.020 and R w =0.025 for 276 reflections with I >3 σ ( I ). The structure consists of isolated VO 4 tetrahedra which surround the La atom to form a LaO 8 dodecahedron. LaV 3 O 9 adopts the monoclinic system: P 2 1 / m with a =4.949(2) A, b =9.547(3) A, c =7.411(2) A, β =100.76(2)°, and Z =2; R =0.035 and R w =0.042 for 1868 reflections with I >3 σ ( I ). The structure adopts a chain-type one consisting of a V 3 O 9 chain along [010] which is made up of edge-sharing VO 5 trigonal-bipyramid pairs and VO 4 tetrahedra. The La atom residues between the V 3 O 9 chains and is coordinated with ten oxygens. The present study demonstrates the applicability of hydrothermal method to the synthesis of new and/or metastable lanthanide vanadates.

LiCoO2 and NaxCoO2 were synthesized through the ion-exchange reaction of CoOOH using the hydrothermal method. The LiCoO2 single phase was obtained at 170°C for 12h in LiOH solutions (≥ 0.1mol/l). T...

A barium vanadium bronze Ba 1+ x V 8 O 21 has been hydrothermally synthesized and structurally characterized. Hydrothermal treatment of a suspension of VO 2 powders in Ba(NO 3 ) 2 solution at 350°C yielded a fibrous brown compound having nonstoichiometric composition Ba 1+ x V 8 O 21 ( x =0.13). Single-crystal X-ray diffractometry revealed the monoclinic system C 2/ m with a =15.144(6), b =3.596(4), c =14.972(3) A, β =90.08(3)°, and Z =2, with the refinement based on 2021 reflections with I >3 σ ( I ) converged to R =0.054 and R w =0.046. A new tunnel-type bronze structure was disclosed in which VO 6 octahedra and VO 5 trigonal bipyramids form a V–O framework with a tunnel cavity running along [010]. The Ba atom partially occupies the tunnel site with more than half occupancy of 56.6%, which causes displacement of the Ba atom and further displacement of V and O atoms along the tunnel axis. Ba 1+ x V 8 O 21 is the first tunnel-type barium vanadium bronze whose structure has been fully determined.

In the SrO–VO2 phase diagram there exists no SrV4O9 phase corresponding to the CaV4O9 phase in the CaO–VO2 diagram and synthesis of SrV4O9 has not been reported so far. We are successful in hydrothermal synthesis of the synthesis of SrV4O9: hydrothermal treatment of SrCl2–NaVO3–(CH3)4NCl solutions above 300°C yielded light-green plate crystals identified as SrV4O9. Single-crystal X-ray diffractometry confirmed the CaV4O9-type structure consisting of V4O9 layers and interstitial Sr atoms: P4/n, a=8.379(2) A, c=5.259(3) A, and Z=2. The refinements based on 826 reflections with I>3σ(I) converged to R=0.039 and Rw=0.048. Temperature variation of magnetic susceptibility exhibits a low-dimensional feature of a broad maximum around 100 K, just like that of CaV4O9. Single crystals of CaV4O9 were similarly grown in the hydrothermal CaCl2–NaVO3–(CH3)4NCl system at 280°C and its single-crystal X-ray study was also made to compare with those of SrV4O9.

This paper describes the role of hydrogen in titanium nitriding using an N 2 –H 2 gas mixture plasma, which is empirically known to enhance the rate of nitriding. The nitrided titanium specimen was characterized by SIMS, ERD, XRD, SEM, and hardness measurements. Optical emission spectroscopy was conducted for plasma diagnostics of the N 2 –H 2 plasma with various partial pressures of H 2 gas. The rate of nitriding was most enhanced when a 60 vol.%N 2 –40 vol.%H 2 gas mixture plasma was applied. The hydrogen content of the titanium nitride layer was in the order of 10 wt.ppm and increased with increasing partial pressure of H 2 gas in the working gas. In N 2 –H 2 plasma, NH, N 2 , N and H radicals were detected as reactive species. The amount of NH radicals was greatest when 30–40 vol.%H 2 gas was added to plasma, while the amount of H radical increased monotonously with the ratio of H 2 gas. Based on the experimental results, we propose that H radicals pick up hydrogen from NH radicals to produce active nitrogen and thus enhance the rate of nitriding.

The effects of high pressure on the magnetic structure of Tb 0.76 Y 0.24 have been investigated by neutron diffraction using a clamp type high pressure cell. Pressure was applied up to about 2.4 GPa and temperature, down to about 10 K. The magnetic structure of Tb 0.76 Y 0.24 exhibits a helical phase both under high pressure and at ambient pressure. The helical pitch shows a lock-in feature below about 100 K. With increasing pressure, the helical pitch is enhanced, and a lock-in feature at low temperature still remains.

Dynamic transformation in the surface structure and the morphology of Pd-deposited Si(111) 7 × 7 surfaces with thermal treatment was observed using ultrahigh vacuum scanning tunneling microscopy (U...

New {sigma}-type layered vanadium bronzes M{sub 0.25}V{sub 2}O{sub 5}{center_dot}H{sub 2}O were hydrothermally synthesized for divalent metals of M = Mg, Co, Ni in addition to the first-reported M = Zn compound. The {sigma}-type structures, consisting of V{sub 2}O{sub 5} layers with three octahedral and one tetrahedral V atoms and interlayer M(H{sub 2}O){sub 4} rectangles, were confirmed by single-crystal X-ray diffractometry. The Ni compound crystallizes in the same P{bar 1} phase as the Zn compound while the Mg and Co compounds crystallize in the new P2{sub 1}/a phase of higher symmetry. The P2{sub 1}/a phases is an undistorted form of the P{bar 1} phases, where the distortion is caused by the locations of interlayer water molecules. Among four V atoms one octahedral atom is tetravalent and others are pentavalent, being consistent with the average V{sup 4.75+} valence. The M(H{sub 2}O){sub 4} is held by two apical oxygens of VO{sub 4} tetrahedra to form a regular MO{sub 6} octahedron and thus M{sup 2+} ions must fit for the octahedral oxygen coordination.

Thermodynamic properties of a Li-Al alloy in the two-phase ({alpha}Al + {beta}LiAl), ({beta}LiAl + {gamma}Li{sub 3}Al{sub 2}), and ({gamma}Li{sub 3}Al{sub 2} + liquid) regions, and in the single {beta}LiAl phase region were determined from electromotive force measurements in a LiCl-KCl eutectic melt at temperatures from 650 to 76f0 K. From the obtained thermodynamic properties, the single-electrode Peltier heat of a Li-Al alloy electrode was evaluated as a function of the alloy composition. It turned out that the single-electrode Peltier heat of a Li-Al alloy electrode exhibits discontinuities at the compositions of coexisting-single phase boundaries. The change of the single-electrode Peltier heat on a phase boundary was interpreted thermodynamically and was found to follow from thermodynamic data for the single phases and the phase diagram data.

Structures of VO2(A) have been redetermined by single-crystal diffractometry for low- (LTP) and high-temperature (HTP) phases at 298 and 473 K, respectively. The LTP adopts the tetragonal systemP4/nccwitha=8.4403(9) A,c=7.666(1) A, andZ=16, whereas the HTP adopts the body-centered tetragonal systemI4/mwitha=8.476(2) A,c=3.824(2) A, andZ=8. The refinements led toR/Rw=0.031/0.032 for LTP and 0.012/0.033 for HTP. The structures of both phases consist of edge-sharing VO6octahedra and exhibit quite similar oxygen frameworks. Through the transition the V4+–V4+bonding in LTP with a distance of 2.7695(8) A is dissociated in HTP to a distance of 3.0794(3) A. The transition occurs with cooperative movements of the V atoms, namely, a rotation around thecaxis and a shift along thecaxis. Strangely, twinning is induced on the LTP to HTP transition but disappears on the reverse transition.

Single crystals ofα-CoV3O8, a mixed-valence compound of VIV/V, were hydrothermally synthesized. It crystallizes in the orthorhombic systemIbamwitha=14.3298(6) A ,b=9.8906(6) A ,c=8.3950(8) A , andZ=8. The structure was refined toR=0.034 andRw= 0.030 for 1558 reflections withI>3σ(I). There are three kinds of metal sites, namely, octahedralM(16k) forM=Co, V(1), tetrahedral V(2) (8j), and trigonal-bipyramidal V(3) (8j), where theMsite was found to consist of half-occupied Co and V(1). Its polyhedral framework is built up ofMO6slabs and V(2)O4–V(3)O5units. TheMO6slab is constructed by linking zigzag chains of edge-sharingMO6octahedra running along thecaxis. The linkage is made along thebaxis by sharing common vertices of O(5) and thus the slab stands in the bc plane. The V(2)O4–V(3)O5unit, playing a role in bridgingMO6slabs, is made of an edge-sharing V(3)O5pair to which two V(2)O4are attached. Valence states of metals were evaluated as CoII, V(1)IV, V(2)V, and V(3)V. The metal distribution over theMsite is basically random but is constrained by a rule to form a Co–O(5)–V(1) group at the linkage ofMO6chains, which accounts for the half-occupancies of Co and V(1) as well as a positional shift of O(5). The structure is compared with those ofα-ZnV3O8andβ-MgV3O8in particular reference to metal distributions. The magnetic susceptibility curve ofα-CoV3O8exhibits a sharp peak at 8 K, suggesting the onset of antiferromagnetic order.

Ba analogues of hewettite (CaV6O16·9H2O) were synthesized by the hydrothermal methods. The compounds exhibit two phases formulated by BaV6O16·nH2O and Ba1+xV6O16·nH2O (x≈0.2,n≈3), and the structure of BaV6O16·nH2O has been determined from a single crystal study. It crystallizes in the orthorhombic systemPnmmwitha=12.162(3) A,b=10.841(4) A,c=17.035(4) A, andZ=6 and the structure refinements led toR=0.066 andRw=0.076 for 1480 reflections withI>3σ(I). The structure is basically analogous to that ofγ-Li1+xV3O8or CaV6O16·9H2O, consisting of V6O16layers and interstitial hydrated Ba atoms. The V6O16layers stack along thecaxis with 8.518-A spacing which is half of thecaxis; adjacent layers are mirror images of each other. Ba atoms reside in three kinds of sites with totally different oxygen coordinations. Their interlayer distributions result in another long period along thebaxis which is triple the ordinary 3.6-A period of the hewettite compounds. This is the first single-crystal structural study of the synthetic hewettite compounds.

Single phase of lithium manganese spinel was synthesized at low temperature by the hydrothermal method. From the result of SEM observation, the particle shape of this specimen was stick type. The chemical formula of this specimen was determined to be Li1.14[Mn0.72Mn4+1.14]O3.93 by ICP analysis and redox titration. The results of differential scanning calorimetry and low-temperature X-ray diffraction showed that the structural phase transition due to the Jahn-Teller distortion was suppressed in this specimen.

The properties of a titanium nitride film prepared by a DC arc plasma jet were investigated by microscopic observations, composition analysis, and hardness measurements. Scanning electron microscopy showed that the film was composed of three phases, designated the A, B, and C regions from the outer surface. The existence of three regions was also supported by composition analysis and hardness measurements on the cross section. XRD patterns showed the presence of δ-TiN in the A region. In the B region, a number of voids were observed, which have never been reported in previous papers. These were made up from specific crystallographic surfaces. The C region also had a few voids which were somewhat different from those in the B region. In the matrix, an acicular texture was found and identified as α-Ti solid solution by XRD. The cross section of the film changed the color determined by the nitrogen content.

Single crystals of Cs 2 V 4 O 11 were obtained in the hydrothermal CsVO 3 –VO(OH) 2 system and its structural chracterization was performed. Cs 2 V 4 O 11 crystallizes in the C -centered orthorhombic system: Cmm 2 with a =5.571(2) A, b =9.639(2) A, c =5.222(2) A and Z =1. Structure refinements based on 402 reflections converged to R =0.037 and R w =0.044. The structure has V 4 O 11 layers and interlayer Cs atoms. The V 4 O 11 layer exhibits an unusual V–O network structure consisting of VO 4 tetrahedra and VO 5 trigonal bipyramids in a random distribution. The structure is derived from that of a fictive V 4 O 10 layer made up of vertex-sharing VO 4 tetrahedra. That is, one-fourth of the shared vertices in the V 4 O 10 layer are converted into shared edges by adding extra oxygens leading to the V 4 O 11 layer; actually a vertex-sharing VO 4 dimer changes to an edge-sharing VO 5 dimer. Consequently the V atom in a single crystallographic site shows two different V–O coordinations of VO 4 tetrahedra and VO 5 trigonal bipyramids in a one-to-one ratio.

Copyright (c) 1997 Elsevier Science S.A. All rights reserved. Conductivity, thermoelectric power (TEP) and magnetic susceptibility of the tunnel-type manganese oxides K 1.5 Mn 8 O 16 are reported. The conductivity and the TEP around room temperature suggest that the electrical conduction is governed by hopping of small-polarons. Three phase transitions are observed at T 1 (varies from 175 K to 215 K, batch-dependent), at T 2 (52 K) and at T 3 (20 K). The T 1 transition is considered to be a charge-ordering transition of Mn 4+ and Mn 3+ coupled with the ordering of the potassium ions in the tunnels. Weak ferromagnetism appears between T 2 and T 3 and disappears again below T 3 . The anisotropic measurement of the susceptibility strongly suggests the occurrence of a helical magnetism below T 3 . After the single crystals are soaked in conc. HNO 3 for a few days, a part of the potassium ions in the tunnels are removed. Besides, the activation energy is drastically reduced and the T 1 transition is suppressed. This suggests that the charge-ordering of Mn 4+ and Mn 3+ is very sensitive to the state of the tunnel cations.

Single crystals of hydrated vanadium oxides with layered structures containing divalent Ca or Ni were hydrothermally grown, and their structural characterization was focused on the interlayer sites. Both compounds are formulated by M 0.25 V 2 O 5 ·H 2 O, M =Ca, Ni and crystallize in the monoclinic system C 2/ m with Z =4: a =11.692(2), b =3.564(1), c =10.986(2) A, b =105.42(1)° for M =Ca; a =11.756(1), b =3.649(1), c =10.364(2) A, β =95.03(1)° for M =Ni. The structures consist of δ -type V 2 O 5 layers stacking along the c axis and interlayer hydrated M 2+ ions; the δ refers to the V 2 O 5 layer of δ -Ag 0.68 V 2 O 5 after which the compounds are designated δ - M 0.25 V 2 O 5 ·H 2 O. The M atoms partially occupy interlayer sites of the 2 c position for M =Ni and the 4 i position for M =Ca, to each of which four water molecules (O w ) are attached forming M O w4 rectangles. M and O w site occupancies indicate that the M O w4 rectangles are distributed so that they do not interact with each other, and the above stoichiometric formula correspond to the maximum occupancies. Bonding to three apical oxygens of the V 2 O 5 layers, the Ca atom forms a CaO 7 polyhedron, and to two apical oxygens the Ni atom forms a NiO 6 octahedron, due to the Ca 2+ ion being larger than that of Ni 2+ ion. This is the first single-crystal study on the structures of hydrated δ -type vanadium oxide bronzes.

Hydrothermal methods for growing single crystals of alkali-metal trivanadates AV{sub 3}O{sub 8} for A = K, Rb, Cs and their single-crystal structural studies are presented. Plate-shaped orange crystals were hydrothermally grown at 250 C from V{sub 2}O{sub 5} powders dispersed in A(NO){sub 3} solutions. RbV{sub 3}O{sub 8}, the structure of which has remained undetermined, was found to be isostructural with KV{sub 3}O{sub 8} and CsV{sub 3}O{sub 8}: the monoclinic system P2{sub 1}/m with a = 4.9864(8) {angstrom}, b = 8.442(1) {angstrom}, c = 7.8621(7) {angstrom}, {beta} = 96.064(9), and Z = 2. The crystallographic data for KV{sub 3}O{sub 8} and CsV{sub 3}O{sub 8} have been revised; in particular, the data of KV{sub 3}O{sub 8} has been greatly improved. AV{sub 3}O{sub 8} adopts a layered structure with V{sub 3}O{sub 8} layers consisting of VO{sub 6} octahedra and VO{sub 5} square pyramids. The oxygen coordination around interlayer A atom is AO{sub 8} for A = Rb, Cs but is regarded as AO{sub 6} for A = K from the anomalous variation of A-O distances with A{sup +} ionic radii.

Ferromagnetic materials, magnetite crystals, have been extracted and identified from magnetotactic bacteria, polyplacophoran mollusks (chitons), salmons, tuna and recently tissues of the human brain. Ferritin, the iron storage nonheme-protein contains hydrated iron oxide (Fe_2O_3 • nH_2O) in its core. It is suggested that this hydrated oxide in ferritin would be the precursor of magnetite in both magnetotactic bacteria and the chitons. Many studies have described that ferritin were related with cell proliferation, specially tumor cell growth. In this study, we attempted to investigate the presence of magnetite in tumor tissues. We report the first detection of magnetic materials in various human tumor tissues (melanoma, breast, ovary, testicle, sarcoma, meninginoma, glioblastoma, astrocytoma, glioma, metastasis) with the use of SQUID magnetometry. The magnetometory data for the magnetic materials are consistent with magnetite (Fe_3O_4). Its concentration of various tissue types were measured via sIRMs. Tumor tissues were also stained blue with the Perls staining method for detecting ferritin. Our experiments show that the distribution of magnetite and ferritin in tumor tissues might depend on the etiology of the tumor. Ferritin distribution as indicated through staining suggest an irregular pattern with distinctive foci. However, a spacial covariance between ferritin and magnetite was unable to demonstrate in this study.

Hydrous vanadium (IV, V) oxides containing K or Rb were synthesized by the hydrothermal method from VOSO{sub 4}-M{sub 2}SO{sub 4} (M = K, Rb) solutions. they were found to be isomorphous with previously reported Ba{sub 0.4}V{sub 3}O{sub 8}(VO){sub 0.4}{center_dot}nH{sub 2}O, whose structure consists of V{sub 3}O{sub 8} layers which are bridged by V-O units (denoted by (VO){sub 0.4} in the formula) forming a tunnel-like opening to accommodate hydrous Ba ions. The isomorphous compounds can be formulated by J{sub x}V{sub 3}O{sub 8}(VO){sub y}{center_dot}nH{sub 2}O (M = K, Rb, Ba; n = 0.6--0.7) where x and y show similar values of less than 0.5 as is accounted for by the crystal structure. The formation of this phase seems to be governed by the size of M cation whose ionic radius should lie in a limited range of 1.35 to 1.52 {angstrom}. The V{sub 3}O{sub 8}(VO){sub y} framework structure of a bronze-like type is compared with the V{sub 2}O{sub 5} framework of {beta}-M{sub x}V{sub 2}O{sub 5} ({beta} bronze) and the V{sub 3}O{sub 8} framework of H{sub 2}V{sub 3}O{sub 8}.

The effect of the gas composition in N2-H2, gas mixture plasma on the growth rate of titanium nitride layers was investigated by optical emission spectroscopy (OES), microscopic observation, and X-ray diffractometry. The growth rate of nitride layers was enhanced by hydrogen addition, which was the highest at 50vol.%N2-50vol.%H2. The results of the spectroscopic measurements and microscopic observations indicate that NH radical intensity is correlated with the growth rate of nitride layers. It is suggested that NH radical plays the most significant role during nitriding process. XRD analysis shows that the compound layers consists of TiN and Ti2N. In the diffusion layers, acicular textures were observed by microscopic observation.

A new layered vanadium bronze designated as σ-phase Zn0.25V2O5· H2O has been hydrothermally synthesized from ZnCl2and VO(OH)2. A single-crystal study revealed the triclinic systemP 1 :a= 10.614(2) A,b= 8.031(3) A,c= 10.7688(9) A, α = 90.65(1)°, β = 91.14(1)°, γ = 90.09(2)°, andZ= 8. The structure was solved and refined toR/Rw= 0.079/0.048 for 1580 reflections withI> 3σ(I), which consists of V2O5layers stacking along thecaxis and interstitial hydrated Zn2+ions. The V2O5layer adopts a novel polyhedral framework built up of VO6octahedra, VO5trigonal bipyramids, and VO4tetrahedra. When projected parallel to theabplane, the V2O5layer is described by the atomic sheet model in a manner similar to the V2O5layer of δ phase such as δ-AgxV2O5, that is, a double-sheet type composed of two V2O5sheets facing each other. The interstitial Zn atom forms a ZnO6octahedron with two apical oxygens of the VO4tetrahedra on opposide sides and with four coplanar water molecules. The anhydrous σ phase was obtained by heating the hydrate up to 200°C accompanied by the contraction in layer spacing from 10.76 to 8.92 A.

The crystal structure of K–Cr oxide of hollandite type synthesized under high pressure and high temperature was determined by the single crystal X-ray diffraction method. The compound crystallizes with the tetragonal symmetry of the space group I 4/ m , the cell parameters a = 9.7627(4) and c = 2.9347(6) A, and Z = 1. The structure refinement based on 572 unique reflections (2θ R = 0.0296. The experiment confirmed that the chemical composition was stoichiometric, K 2 Cr 8 O 16 , in which the tunnel sites were fully occupied by K ions without displacement from the special position (2 b ). The result suggests that the high pressure induces a high cation occupancy in the tunnel and opens a way to control the occupancy and some physical properties related to tunnel cations.

Atomic force microscopy (AFM) was used to determine the atomic configuration and topography of the surface of KMn 8 O 16 , a powdered form of α-manganese dioxide (α-MnO 2 ) containing K ions. By depositing the powder on mica, we were able for the first time to use AFM to image the surface of the powder. We took three types of images: low-resolution, wide-scan (5×5 μm 2 region); high-resolution (500×500 nm 2 region); and atomic-scale (10×10 and 2×2 nm 2 regions). The low-resolution imaging showed that the powder has needle-like crystallites. The high-resolution imaging showed that the surface of the powder has a “faceted” structure. The atomic-scale imaging revealed that the facet plane has a hill-and-valley structure with a height difference of 0.2–0.3 nm along the crystal C axis. Furthermore, the surfaces of the hills were (110) surfaces, and those of the valleys were surfaces formed by the removal of O–Mn–O units from these (110) surfaces. Atomic-scale imaging of a hill shows a periodic structure that corresponds to the configuration of surface hydroxyl species and bridging oxygen atoms of the (110) plane. The close agreement that we found when we superimposed the atomic-scale images and the bulk structure projection indicates that there is no reconstruction on the (110) surface of powdered KMn 8 O 16 .

FeVO 4 -II, a metastable phase so far produced under high pressures, has been synthesized by a hydrothermal method from a solution of VOCl 2 and FeCl 3 . FeVO 4 -II crystallizes in the orthorhombic system: Cmcm , a = 5.6284(7) A, b = 8.2724(7) A, c = 6.1118(6) A, with Z = 4. The single-crystal structure refinements verified a CrVO 4 -type structure and converged to R/R w = 0.035/0.029 for 324 reflections with I > 3σ( I ). The structure consists of FeO 6 octahedra and VO 4 tetrahedra where edge-sharing FeO 6 octahedra form isolated FeO 4 chains running parallel to the c axis and the chains are joined by VO 4 tetrahedra. The temperature dependence of magnetic susceptibility featured by a broad maximum around 52 K suggests the predominance of one-dimensional antiferromagnetic interactions in the FeO 4 chains. A three-dimensional antiferromagnetic order is attained somewhere below 40 K yielding a hyperfine field of 483 KOe at 4.2 K observed in the Mossbauer spectrum.

Ferritin, the iron storage nonhaeme-protein contains a ball of hydrated iron oxides (Fe2O3⋅nH2O) in its core, which is paramagnetic at room temperature. It is reported the hydrated iron oxide is the precursor of magnetite (Fe3O4) in the magnetotactic bacteria and polyplacophoran mollusks. It is not known whether this is the case for other organisms. In our study, we report the first detection of magnetic material in the human brain through the use of SQUID magnetometry. The material was characterized by HRTEM and EPMA. It was affirmed the material was a single crystals of magnetite. Magnetite distribution in tissues might be related with ferritin, if the core of these molecules are involved in magnetite formation in human. In general, both Perls staining and MRlmaging methods are adopted routinely for determining the relative amounts of Fe(+III) in the whole brain, which is dominated by ferritin. Both methods suggested high levels of Fe(+III) distribution in the globus pallidum, putamen, caudate, internal cerebral capsule of the cerebrum, red nucleus of the mid brain and lower concentrations in the substantia nigra of the mid brain and the dentate nucleus of the cerebellum. Whereas, our experiments showed that the distribution of magnetite is rather even in the whole human brain averaging 4 ng per gram of tissue (except for the meninges, where it is 20 times higher).

Rb0.5V2O5, an anhydrous phase of the rubidium intercalate, has been synthesized in a hydrothermal VO(OH)2–RbCl system. It crystallizes in the monoclinic system C2/m: a= 11.596(2), b= 3.6908(9), c= 9.723(l)A, β= 100.93(1)° and Z= 4. A single-crystal study (R/Rw= 0.069/0.079) revealed that the V2O5 layers are isostructural with those of K0.5V2O5 in Part 4 which consist of zigzag chains of edge-sharing VO6 octahedra. The interlayer Rb atom forms an RbO8 rectangular prism with the apical oxygens of the VO6 octahedra in contrast to the KO7 coordination in K0.5 V2O5˙Rb0.5V2O5 with 9.55 A spacing was oxidized by hydrogen peroxide to a hydrated phase, Rb0.4V2O5˙0.8H2O with 10.85 A spacing. This compound was reduced by rubidium iodide to a less hydrated phase, Rb0.4V2O5·0.5H2O with 10.41 A spacing, rather than to Rb0.5V2O5. Interlayer sites for monovalent cations in anhydrous phases are suggested to be correlated with cationic sizes and contents.