Fe In Ti Research Articles

Geochemical characteristics and implications of epidote in South Dulan and Vlaska exploration greenfield in north of Bor metallogenic zone, Serbia

The Bor metallogenic belt in Serbia is a promising region for copper-gold (Cu-Au) resources, hosting numerous porphyry copper deposits, epithermal gold deposits and metallogenic prospects, such as the South Dulan and Vlaska exploration greenfield. Epidote alteration is integral to the propylitic and sodic-calcic alteration assemblages within this region. It is distinguished by the extensive occurrence of two primary epidote types: disseminated (Ep1) and veined (Ep2) epidote. In this study, comprehensive petrographic analysis reveals that in the propylitic zone, epidote mainly replaced hornblende (Ep1a) and plagioclase phenocrysts (Ep1b), coexisting with chlorite, apatite and titanite. In proximity to the potassic zone, epidote (E1c) coexists with biotite, while epidote (Ep2), chlorite, pyrite and chalcopyrite veinlets are observed near the ore body. Notably, Ep1 exhibits lower Fe and higher Mn contents in comparison to Ep2. Additionally, elements such as Ca, Al and Fe in Ep1a, and Ca, Fe, Mg, Mn and Ti in Ep1b, as well as Ca, Al, Fe and Mn in Ep1c, are introduced into the epidote through hydrothermal fluid interactions. Variations in trace element characteristics are evident among different epidotes. Specifically, Ep1a exhibits elevated Mg content (324–6050 ppm), Ep1b is notable for its high Na (22–942 ppm) and Sr (523–3075 ppm) contents, while Ep1c contains elevated K (24–445 ppm) and Na (41–103 ppm). Which suggest that disseminated epidote (Ep1) inherits the geochemical features from its precursor minerals. In comparison to disseminated epidote, epidote in veinlet exhibits higher Fe3+, Cu, Sn and REEs, along with lower contents of Pb, Sb and Sc, suggesting that these elements have been integrated into epidote through isomorphism substitution and influenced by fluids compositions, physical factors (temperature, pressure, etc.) and chemical parameters (speciation, pH, fO2, etc.), as well as mineral assemblages. Therefore, the trace element contents of Pb, Sb, Sc, Cu, Sn and REEs in epidote could serve as more appropriate indicators for mineral geochemistry in porphyry deposit hydrothermal centers.

Effect of the Nature of Both Cation and Anion Substitution on the Structural Symmetry of Li‐Rich 3d‐Metal Chalcogenide Electrodes

AbstractLi‐rich layered chalcogenides have recently led to better understanding of the anionic redox process and its associated high capacity while providing ways to overcome its practical limitations of voltage fade and irreversibility. This study reports on the feasibility of triggering anionic activity in Li2TiS3, through anionic substitution (Se for S) or cationic substitution (Fe for Ti). Herein, the chalcogenide chemical space is further explored to prepare mono‐substituted Li1.7Ti0.85Mn0.45Ch3 (Ch = S/Se) and doubly substituted cationic and anionic phases (Li1.7Ti0.85Fe0.45S3‐zSez) which crystallize either in the O3‐ or O1‐type structures depending upon substituents. All series show a bell‐shape capacity variation as function of the transition metal (TM) substitution degree with values up to 240 mAh g−1. For specific compositions, a structural O3 to O1 phase transition is observed upon Li removal, which is not reversible upon Li re‐insertion due to kinetic limitations and negatively affects long‐term cycling performance. Density functional theory (DFT) calculations confirm the O3/O1 relative stability along the different series and point subtle electronic differences in the TM‐doping, rationalizing the structural and electrochemical behaviors of these phases upon cycling. These findings provide further insights into the link between structural and electronic stability, which is of key importance for designing chalcogenide‐based anionic redox compounds.

Evaluation of electrochemical performance and redox activity of Fe in Ti doped layered P2-Na0.67Mn0.5Fe0.5O2 cathode for sodium ion batteries

Here, we report a wet synthesis-based titanium doping strategy to improve the structural stability and electrochemical performances, such as cycling stability and rate capability, of P2-type Na0.67Fe0.5Mn0.5O2 layered oxide cathodes. Through Ti4+ doping aimed at replacing some of the Mn and Fe atoms in the crystal structure, effective mitigation of the Jahn Teller distortion caused by active Mn3+ before charging and Fe4+ after charging was achieved. X-ray diffraction (XRD), Raman spectroscopy, Electrochemical Impedance Spectroscopy (EIS) and Mössbauer spectroscopy were used to investigate the effects of the Ti4+ dopant before and after cycling. It was observed that Ti4+ doping increased the Na layer thickness, minimized the lattice volume strain, showed better structural stability, minimally decreased Fe migration to the Na layer, and lowered charge transfer resistance in these P2-type cathodes. Overall, our reported synthesis methodology and electrochemical characterizations highlight the feasibility of Ti doping in sodium layered oxide P2-type cathodes.

Designing new tetragonal Heusler materials using V, Cr, Fe and Ni doped Ti2CoGa: A first-principles study

In this work, the structure and potential tetragonal distortion (TD) properties of Ti2CoGa and its M−doped (M = V, Cr, Mn, Fe, Ni) system are studied in detail by first-principles calculations. The result shows that Ti2CoGa alloy should crystalize in cubic L21-type structure and no tetragonal distortion is discovered, which limits its application. Attempts are made to seek new tetragonal Heusler materials by replacing Ti or Co atoms in Ti2CoGa with element M (M = V, Cr, Mn, Fe, Ni). It is found that all the Ti2Co1−xMxGa (x = 0.25, 0.5, 0.75; M = V, Cr, Mn, Fe, Ni) compounds tend to form L21 structure, and only Ti2Co1−xNixGa has the possibility of TD when x > 0.29. For Ti2−xMxCoGa (x = 0.25, 0.5, 0.75) system, the increase of the doping amount results in the cubic ground state of the alloy turning from L21 to XA structure. Furthermore, energy curves with different structures show that the tendency of TD in the alloy can be excited after substitution V (x = 0.29–0.50), Cr (x = 0.31–0.43) and Fe (x = 0.21–0.29) for partial Ti. This research can inspire us to search and realize new tetragonal Heusler materials by suitable doping in ternary Heusler alloys.

Enhancement of the tensile strength by introducing alloy element Fe for Ti based alloy

The stability and the mechanical properties of β type Ti1-xFex binary alloys were systematically studied by means of first-principles calculations based on the density functional theory. Our results have demonstrated that the Ti1-xFex alloys in our consideration are stabilized as β phase and the formation energy decrease with the increase of alloy element Fe content. It is found that the mechanical parameters, such as Young's modulus E, shear modulus G and bulk modulus B almost linearly increase when the concentration of alloy element Fe increase for x ranging from 0.0625 to 0.5. Differently, the Poisson's ratio ν is decreased monotonously with the increase of Fe content. According to the stretching model, we have shown that the tensile strength of the Ti1-xFex alloys is significantly enhanced when we increase the concentration of the alloy element of Fe. The enhancement of the tensile strength is mainly contributed from the improvement of bond strength between Ti–Fe induced by the concentration of Fe according to analysis of the charge density and electron localization function. Our results indicate an effective way to improve the tensile strength as well as the toughness of Ti-based alloy for the application in aerospace industry and marine engineering.

An effective way to solve the abnormal oxidation behavior of Fe in Ti(C,N)-304ss cermet

WC and TiB2 were added into Ti(C,N)-304ss cermet to relieve an abnormal oxidation behavior of Fe in this cermet. During high-temperature oxidation (650 °C), the volume swelling of WO3 eliminated the gap led by the volume shrinkage of TiO2. Liquid B2O3 covered the oxidation surface or filled in cracks, forming a dense oxidation layer. As a result, the abnormal oxidation behavior was relieved. The oxidation mechanism was investigated using FESEM, XRD, LSCM, and AFM. Fe atoms outward diffused to the surface along with the TiO2/304ss boundary forming ring-structure oxide and across the TiO2 generating aggregated oxide on TiO2 surface.

Abnormal oxidation behavior of Fe in Ti(C,N)-304ss cermet during early oxidation stage

In this work, the oxidation experiments of Ti(C,N)- 304 stainless steel (304ss) cermet were carried out at 650 °C in the air. Abnormal oxidation behavior of Fe in the Ti(C,N)- 304ss cermet was observed for the first time, and it was investigated by field emission scanning electron microscope (FESEM) and 3D laser scanning confocal microscope (LSCM). A gap was generated in the TiO2/304ss interface due to the volume shrinkage led by the oxidation of Ti(C,N). When the tip of the gap propagated to the Cr-depleted region in 304ss, Fe atoms in this area reacted with O atoms and formed iron-contain oxides. Cations (Fe3+ and Ti4+) in oxidation products interdiffused to each other and formed Fe2TiO5 in the gap at high temperature. The gap is a rapid diffusion path for atoms, and Fe atoms outward diffused along the gap to the oxidation surface and formed Fe2O3 covering the oxidation surface.

Ferromagnetism in Cr-, Fe-, and Ni-doped TiO2 samples

Ferromagnetic Cr-, Fe-, and Ni-doped TiO2 nanopowder samples (with 0.2% Cr, Fe, or Ni) were synthesized using the solid-state reaction method. The X-ray diffraction pattern showed that all the samples possessed typical anatase structure, and no other impurity phases were observed. Ultraviolet–visible spectroscopy (UV–vis) measurements revealed that the band gap decreased due to the incorporation of Cr, Fe, or Ni. The photoluminescence results showed the presence of oxygen defect related emission peaks in Cr-, Fe-, and Ni-doped TiO2. Room temperature ferromagnetism is observed in all the Cr-, Fe-, and Ni-doped TiO2 samples. Saturation magnetic moment is the highest for Fe-doped TiO2. The Fe:TiO2 samples were found to have a magnetic moment of 4.58µB/Fe, and they seem to have greater ferromagnetism than the Cr/Ni-doped TiO2 samples. The structural and magnetic investigations demonstrate that ferromagnetism at room temperature is an intrinsic property of the samples. Thus, ferromagnetism does not originate from clusters or secondary phases; it is due to the Cr/Fe/Ni:TiO2 matrices. This study has shown that substituting a very light percentage of Cr, Fe, or Ni for Ti in TiO2 gives rise to appreciable room temperature ferromagnetic ordering useful for spintronic applications.

High Lithium-Ion Conducting Nasicon-Type Li1+x-YAlxNbyTi2-x-Y(PO4)3 Solid Electrolyte

Recently, the demand of a high energy density battery for electric vehicles (EVs) has been significantly increased, because the driving range of EVs with conventional lithium-ion batteries is too short compared with vehicles with internal conversion engines. Lithium-air batteries are attractive candidate for the high specific energy density batteries, because of their high theoretical energy density as 3560 Wh kg-1 for the non-aqueous and 1910 Wh kg-1 for the aqueous system. Non-aqueous systems have some severe problems that still need to be addressed such as decomposition of the electrolyte by the reaction product, lithium corrosion by water, and high polarization for reduction of the reaction product of Li2O2. While, some of these problems are not appreciable to the aqueous system. The aqueous system cannot operate without a water stable lithium metal electrode, because lithium reacts violently with water. The idea of the water stable lithium electrode was proposed by Visco et al. in 2004 [1]. The lithium metal was separated with an aqueous electrolyte by the water stable NASICON-type lithium conducting solid electrolyte of Li1+XAlxTi2-x(PO4)3. In the last half century, many types of high lithium-ion conducting solid electrolytes have been reported, the conductivities of which are in a range of 10-4-10-2 S/cm at room temperature. Of them, Li1+xAxTi2-x(PO4)4 and Li7La3Zr2O12 were reported to be stable in the LiCl saturated aqueous solution. The stability in the aqueous solutions is essential for the lithium protect solid electrolyte in aqueous lithium-air batteries. The Ta doped Li7La3Zr2O12 exhibited a high lithium ion conductivity of 1x10-3 S cm-1 at 25 °C and is stable in contact with lithium metal, but it is difficult to prepare a thin film, because of lithium evaporation during the high temperature sintering. The thin film of Li1+xAxTi2-x(PO4)4 was prepared by a tape casting method and the ion conductivity of the Li1.4Al0.4Ti1.6(PO4)3-3wt% TiO2 film was 7.7 x10-4 S cm-1at 25 °C [2]. . Since the report by Aono et al. in 1989 [3], the NASICON-type lithium-ion conducting solid electrolytes have been extensively examined. Zhang et al. reported that the electrical conductivity of Li1+xAlxTi2-x(PO4)3 was enhanced by a partial substitution of Ge, Co, and Fe for Ti. The highest ion conductivity of 1.3×10-3 S cm-1 at 25 °C was observed in Li1.4Al0.4Ge0.2Ti1.4(PO4)3. In this study, we have examined dependence of the substitution of Nb5+ for Ti4+ in Li1+xAlxTi2-x(PO4)3 on the electrical conductivity and mechanical properties. Ionic radius of Nb5+(0.064 nm) is slightly higher than that of Ti4+ (0.061 nm) and higher than that of Ge4+ (0.053 nm). Nb2O5 is considerably cheaper than GeO2. Li1+x-yAlxNbyTi2-x-y(PO4)3 was synthesized in a range of x=0-0.60 and y=0-0.4 using a conventional solid-state reaction method. The lithium-ion conductivity of 7.5×10-4 S cm-1 and three-point bending strength of 67 N mm-2 for Li1.3Al0.5Nb0.2Ti1.3(PO4)3 and the lithium-ion conductivity of 3x10-4 S cm-1 and the three-point bending strength of 120 N mm-2 for Li1.35Al0.55Nb0.2Ti1.25(PO4)3at room temperature were observed. The water-stable high lithium-ion conducting solid electrolytes with excellent mechanical properties have potential applications for lithium-air batteries.

Na1+XFexTi2-X(PO4)3/C (x = 0-1) Electrode Materials for Na-Ion Batteries

Lithium resources are unevenly distributed worldwide and might not meet the increasing global demand for energy. Rechargeable Na-ion batteries can be considered as a serious alternative due to the natural abundance and the low cost of sodium especially for electrical energy storage associated with the deployment of sustainable and renewable energy sources. In addition, aqueous electrolytes improves the safety of the batteries and are environmentally benign. Thus, there is an increasing interest in the research of new electrode materials that can be used in such systems. Transition metal phosphates with NASICON structure are good candidates due to their high ionic conductivity and the possibility of tuning the potential by selecting the transition metal. However, they present low electronic conductivity that require doping, nanostructuration or coating to improve electrochemical performances. Na1+xFexTi2-x(PO4)3/C composites, with x=0-1, could be used as anode or cathode materials for Na-ion batteries since they exhibit three different potential plateaus at 4 V, 2.2 V and 0.4 V vs. Na+/Na0 depending on the amount of inserted Na+. These composite materials were obtained by solid state reaction with sucrose as carbon source for conductive coating and were characterized by different experimental and theoretical methods (Figure 1). The electrochemical mechanisms were identified from operando techniques, especially for the intermediate potential plateau at 2.2 V vs. Na+/Na0 that is related to changes in the oxidation states of both Ti and Fe. For example, the reduction of Fe3+ into Fe2+ was observed at the beginning of the discharge from 57Fe Mössbauer spectroscopy. High electrochemical performances were obtained at this potential including long cycle lifetime, high specific capacity and high power rate that are explained by the morphology of the particles, the carbon coating and the substitution of Fe for Ti (Figure 2). Acknowledgments Financial supports by Campus France (PHC Toubkal 008/SM/13), the Centre National de la Recherche Scientifique (CNRS, France), the Centre National de la Recherche Scientifique et Technique (CNRST, Maroc), the Institut de Recherche en Energie Solaire et en Energies Nouvelles (IRESEN, Maroc), the Swedish Research Council (contract 2012-3392) and StandUp for Energy (Sweden) are gratefully acknowledged. Figure 1

Role of iron in Na 1.5Fe 0.5Ti 1.5(PO 4) 3/C as electrode material for Na-ion batteries studied by operando Mössbauer spectroscopy

The role of iron in Na 1.5Fe 0.5Ti 1.5(PO 4)3/C electrode material for Na batteries has been studied by 57Fe Mossbauer spectroscopy in operando mode. The potential profile obtained in the galvanostatic regime shows three plateaus at different voltages due to different reaction mechanisms. Two of them, at 2.2 and 0.3 V vs Na +/Na 0, have been associated to redox processes involving iron and titanium in Na 1.5Fe 0.5Ti 1.5(PO 4)3. The role of titanium was previously elucidated for NaTi 2(PO 4)3 and the effect of the substitution of Fe for Ti was investigated with 57Fe Mossbauer spectroscopy. We show that iron is an electrochemically active center at 2.2 V with the reversible Fe 3+/Fe 2+ transformation and then remains at the oxidation state Fe 2+ along the sodiation until the end of discharge at 0 V.

The mineralogy, geochemistry and health risk assessment of deposited particulate matter (PM) in Kraków, Poland

One of the most important air contaminants in Krakow is particulate matter (PM), especially during winter months. Deposited PM was sampled between November 2014 and January 2015 and November 2015 and January 2016. The PM deposition amounted to 0.0646 g/m2 per day in the centre of Krakow and 0.0328 g/m2 in the northern district of the city. The allowed value of annual dust deposits (0.547 g/m2 per day) was not exceeded. The XRD and SEM-EDS analysis showed that quartz, calcite, potassium feldspar, plagioclase, kaolinite, and gypsum were the main mineralogical components of the deposited PM. Only in a few samples were illite, dolomite, and apatite observed. Significant concentrations were measured (ICP-MS) for Ca, Fe, Mg, Al, K, Si, Na, and Mn, and high concentrations for Ti, Cu, Zn, As, Pb, Cr, Ti, V, Li, Sr and Ni. The highest estimated daily intakes (EDI) for resuspended PM, were stated for ingestion exposure pathway than for dermal contact, and finally for inhalation, both for children and adults, as well as, for carcinogenic and non-carcinogenic elements. The mean hazard quotient (HQ) values for all three exposure pathways decreased in the following order: Fe > Al > Zn > Mn > Sr > Cu > Ba > Cr > Pb > V > Ni > Li > As > Sn > Zr > Co > Cd > Be, for children and adults. The hazard index values for all elements in each exposure pathway (HIelem) and for single elements in all exposure pathways (HIpath) were <1, both for children and adults. The risk values from all three exposure pathways were unacceptable in the case of Cr, both for children and adults, and in the case of As for children. The total non-carcinogenic risk (HItotal) values in all three exposure pathways for all elements were <1, however in case of children the risk value pointed to a low risk level. The total carcinogenic risk (Rtotal) values in all three exposure pathways for As and Cr exceeded the acceptable level, both for children and adults.

Single spin channels in Fe-doped CoTiSb semiconductor

The Fe-based single atomic chains are designed in the semiconductive CoTiSb matrix by continuously substituting Fe for Ti, Ti–Sb or Co in [001] crystallographic direction. The electronic structures and magnetic properties of CoTiSb supercells with the Fe-based single atomic chains have been investigated using the first-principles calculations. We predict that the single atomic chains of Fe–Sb (achieved by substituting Fe for Ti) and Fe-vacancy (achieved by substituting Fe for Co) show a 100% spin polarization and form a very small single spin channel. The single atomic chains of Fe–Fe (achieved by substituting Fe for Ti and Sb) show a spin-gapless characteristic.

Effect of Fe Addition on the Microstructure Formation and Mechanical Properties of Ti-2.0, 3.0at%Mo Alloys

Abstract. Ti-Mo based alloys have been used as biocompatible materials. Recently the positive use of inexpensive alloying elements becomes important to develop low cost Ti alloys. The purpose of the present study was to reveal the effect of Fe in Ti-Mo alloy addition on the microstructure formation and mechanical properties. Ti-(2.0, 3.0)at%Mo-(0.0~2.0)at%Fe alloys were arc-melted. The alloy buttons were hot-rolled into about 2.0 mm thick sheets at 10731223 K. Specimens -solid-solution-treated at 1273 K in β phase field were quenched into iced brine. X -ray diffractometry was used to identify phases in the specimens. Microstructures were examined by both optical and transmission electron microscopies. Hardness Young's modulusand of the alloys were evaluated. Addition of Fe in Ti -Mo alloys promote d the formation of athermal omega and increase d in hardness. As-quenched Ti-3at%Mo alloy exhibited mixture of α' and α martensites. The Young's modulus of it was 76 GPa. Ti-2at%Mo-1at%Fe alloy, replacement of 1at%Mo (expensive) by 1at%Fe (inexpensive) from Ti-3at%Mo, also exhibited mixture of α' and α martensites with the Young's modulus of 85 GPa. Hardness of Ti -2at%Mo-1at%Fe alloy, 329Hv, is greater than that of Ti -3at%Mo alloy, 257 Hv. -2at%MoTi-1at%Fe is thought to be a candidate material for a low cost bone replacement Ti alloy with low Young's modulus.

Identification of deposit types of natural corundum by PIXE

Natural corundum, one of the most important exports of Thailand, is a rare, durable and valuable gemstone. The value of these precious stones is determined by their visual appearances, including brilliance, color, fire (light dispersion) and luster. Corundum is an allochromatic mineral whose trace element concentration depends on the origin and has influence on price setting. This work attempts to use an alternative method to identify the geological deposits of rubies and sapphires found in the Thai market which came from various countries, e.g., Africa, Cambodia, Myanmar, Sri Lanka, Thailand and USA. Interrelations between most important major trace elements are the main results of this work. Quantitative analysis of trace elements were performed by particle-induced X-ray emission (PIXE) technique, using 2-MeV proton beam generated and accelerated by the 1.7MV tandem accelerator at Chiang Mai University. The trace elements of interest are Ti, Cr, Fe and Ga. We have found that the relationships between the ratios of trace element concentration can be used to classify the deposit type. Moreover, this method shows a clear separation between two main types of geological deposits, basaltic and metamorphic deposits, which further helps in determining the gemstone origin. For example, the gemstones from Cambodia, Thailand and the USA can be classified as the basaltic deposits with their high concentration in Fe but low in Ti, while the gemstones from Africa, Myanmar and Sri Lanka are metamorphic deposits because they have low Fe but high Ti concentrations. Both deposits required plots of pairs of trace elements and their ratios in population field appearance in order to distinguish their origins. The advantageous of these methods appear to be a new and a sustainable procedure for determining gemstone origins.

The Ti-Fe-P system: phase equilibria and crystal structure of phases

Abstract Abstract Phase equilibria was investigated in the Ti-Fe-P system at T = 1070 K in the region 0–67 at.% of P, employing X-ray powder diffraction. The two ternary compounds, namely Ti0.5–0.8Fe1.5−1.2P (Co2Si-type; space group Pnma; a = 0.5964(2)–0.6011(3), b = 0.3575(3)–0.3600(1), c = 0.6828(2)–0.6882(2) nm) and Ti0.85−1.25Fe1.15−0.75P (ZrNiAl-type; space group P-62m; a = 0.6071(4)–0.6117(1), c = 0.3510(9)–0.3506(1) nm) exist in the Ti-Fe-P system at this temperature. The crystal structure of the Ti0.85–1.25Fe1.15−0.75P compound was additionally determined by X-ray single crystal diffraction on the phase with stoichiometric composition. The substitutions of Ti by Fe were observed for Ti5P3.16, Ti3P and TiP phases, and Fe for Ti in the case of Fe3P, Fe2P binary compounds. Graphical abstract

Structure of epitaxial (Fe,N) codoped rutile TiO2thin films by x-ray absorption

Homoepitaxial thin films of Fe:TiO${}_{2}$ and (Fe,N):TiO${}_{2}$ were deposited on rutile(110) by molecular beam epitaxy. X-ray absorption near edge spectroscopy (XANES) spectra were collected at the Ti L-edge, Fe L-edge, Ti K-edge, O K-edge, and N K-edge. No evidence of structural disorder associated with a high concentration of oxygen vacancies is observed. Substitution of Fe for Ti could be inferred, and secondary phases such as Fe${}_{2}$O${}_{3}$, Fe${}_{3}$O${}_{4}$, and FeTiO${}_{3}$ can be ruled out. The similarity of the N K-edge spectra to O, and the presence of a strong x-ray linear dichroism signal for the N K-edge, indicates that N is substitutional for O in the rutile lattice and is not present as a secondary phase such as TiN. Simulations of the XANES spectra confirm substitution, although N appears to be present in more than one local environment. Neither Fe:TiO${}_{2}$ nor (Fe,N):TiO${}_{2}$ exhibit intrinsic room temperature ferromagnetism, despite the presence of mixed valent Fe(II)/Fe(III) in the reduced (Fe,N):TiO${}_{2}$ film.

Hezuolinite, (Sr,REE)4Zr(Ti,Fe3+,Fe2+)2Ti2O8(Si2O7)2, a new mineral species of the chevkinite group from Saima alkaline complex, Liaoning Province, NE China

Hezuolinite is a new mineral species occurring as an accessory mineral in the Saima alkaline complex in Liaoning Province, NE China. The mineral occurs in a green-aegirine nepheline syenite as non-metamict grains and is associated with microcline, nepheline, aegirine, biotite, eudialyte, rinkite and titanite. The anhedral crystals are several hundred micrometres in size. The mineral is black with dark-brown streak. It is translucent with a resinous luster. Cleavage or parting was not observed. It is brittle with a conchoidal fracture. The hardness is VHN 100 683–964 kg mm −2 (5.5–6 on Mohs’ scale). The measured density is 4.28 g cm −3 , and the calculated value is 4.30 g cm −3 from the empirical chemical formula. Optically, hezuolinite is biaxial negative, with n > 1.8 and 2V = 75°. The dispersion is strong with r > v . The mineral shows a strong pleochroism, from pale brown to dark brown. The average of twenty-five analyses leads to the empirical formula (Sr 2.15 Ce 0.55 La 0.49 Ca 0.49 Na 0.12 Nd 0.09 Pr 0.03 Th 0.03 Sm 0.01 Eu 0.01 ) ∑3.98 (Zr 0.82 Fe 2+ 0.14 Hf 0.02 Mn 0.01 ) ∑1.00 (Ti 1.38 Fe 3+ 0.36 Fe 2+ 0.14 Al 0.04 Nb 0.02 ) ∑1.94 Ti 2 O 8 (Si 2.01 O 7 ) 2 , on the basis of O = 22. The simplified formula is (Sr, REE ) 4 Zr(Ti,Fe 3+ ,Fe 2+ ) 2 Ti 2 O 8 (Si 2 O 7 ) 2 , ideally Sr 2 REE 2 Zr(Fe 2+ )Ti 3 O 8 (Si 2 O 7 ) 2 . The five strongest reflections in the X-ray powder-diffraction pattern [ d in A (I)( hkl )] are: 2.98(100)(−204), 3.02(90)(−313), 1.96(90)(024), 2.18(40)(−422), and 2.84(70)(020). The structure was solved and refined in space group C 2/ m , with a = 13.973(3), b = 5.6984(11), c = 11.988(2) A, β = 114.10(1) °, V = 871.3(3) A 3 , Z = 2, to R1 = 0.037, wR2 = 0.097. The structure of hezuolinite is similar to rengeite. The changes of Sr-O, Zr-O and Ti(1)-O distances confirm partial substitutions of REE for Sr, and Fe for Ti. The sites of O(1), O(2) and O(3) of the hezuolinite structure ( C 2/ m ) are split into O(1) and O(1′), O(2) and O(2′), O(3) and O(3′) sites in the rengeite structure ( P 2 1 / a ), respectively. The Si(1)-O(7)-Si(2) angle in hezuolinite is 175.8°, and is significantly less bent than in rengeite (169.7°). The observed systematic extinctions are in agreement with space group C 2/ m . Hezuolinite is a member of the perrierite-subgroup and can be considered as a chemical intermediate between rengeite and perrierite.

Phase stability and hardness of some ternary Ti–Zr based shape memory alloys

The phase stability and hardness of Ti–30Zr–M (M = Nb, V, Cr, Mo, Fe, Ni and Al) shape memory alloys were investigated by structural observations, d-electron alloy design and microhardness tests. Optical microscopy and X-ray diffraction results show that Nb, V, Cr, Mo and Fe are all β-stability elements in Ti–30Zr–M alloys with the effect enhanced by the presence of Zr. The composition of the least stable β-phase alloy values of Nb, V, Cr, Mo and Fe in Ti–30Zr alloys are 12%, 9%, 5%, 3% and 2%, respectively, indicating an increasing sequence of the β-stability ability. Ni and Al show α-stability or moderate effects and the addition of Ni induces the appearance of (Ti, Zr)2Ni phase in Ti–30Zr–5/15Ni alloys. Based on the d-electron alloy design method, the bond order of Ti and alloying atoms (Bo) and the metal d-orbital energy level (Md) are calculated to build the – diagram of Ti–30Zr–M alloys associated with the phase structure identification. The microhardness of Ti–30Zr alloy is increased by addition of a small amount of the alloying element, except for Nb. There is a drop of the microhardness of each Ti–30Zr–M alloys when β phase appears by the addition of more alloying elements.

Enhanced High-Temperature Piezoelectric Coefficients and Thermal Stability of Fe- and Mn-Substituted Na0.5Bi0.5TiO3 Ceramics

Bismuth-based ferroelectric ceramics are currently under intense investigation for their potential as Pb-free alternatives to lead zirconate titanate-based piezoelectrics. The present work evaluated the thermal depoling behavior of various compositions of Na0.5Bi0.5TiO3 (NBT), one of the Bi-based materials of broad interest, through in situ and ex situ measurements of the piezoelectric constant (d33). A range of ceramics was prepared by substituting 0.5–2 at.% of Fe or Mn for Ti. It was found that a low dopant concentration (0.5 at.%) increases the depolarization temperature (Td) with a minimal loss in room temperature d33, allowing for high piezoelectric coefficients at elevated temperatures. For example, 0.5 at.% Fe substitution leads to an enhanced piezoelectric coefficient of d33 of 133 pm/V at an elevated temperature of 180°C. However, with further increase of dopant concentration, Td decreases in both Mn- and Fe-doped NBT. The in situ depoling measurements of 0.5 at.% Fe- and Mn-doped NBT in the present work exhibit the potential for higher temperature applications.