Perovskite Calcium Research Articles

Effect of A‐ or B‐site doping of perovskite calcium manganite on structure, resistivity, and thermoelectric properties

AbstractBismuth‐, lanthanum‐, and molybdenum‐doped calcium manganite (CaMnO3, abbreviated Mn113) are synthesized by solid‐state synthesis route from their respective oxide precursors at a same doping level (x=0.05). Depending on the ionic sizes, trivalent dopants (Bi3+ and La3+) replace Ca2+(A site), while penta/hexavalent dopant Mo5+/Mo6+ replaces Mn4+ (B site) in the Mn113 structure. XRD of all three doped samples confirm formation of single phase. In all three samples, doping causes unit cell volume to expand, while volume expansion is maximum for the Mo‐Mn113. The transport behavior of the doped samples follows small polaron hopping mechanism. Resistivity of the doped samples depends not only on the carrier concentration but also on the effective bandwidth determined by the structural distortion introduced by the dopant ions. Bi‐Mn113 has highest resistivity at the both temperature end, while La‐Mn113 has the lowest. Thermopower is determined by the carrier concentration only and does not depend on dopant type, having value ~260 μV/K at 1000 K. At high (>800 K), S reaches a saturation value and becomes independent of T. La‐Mn113 is having highest figure of merit (zT) 0.19 at 1000 K.

Electrostatic Self-assembly Deposition of Layered Calcium Niobate Intercalated with Task-specific Ionic Liquid and Its Electrocatalytic Activity

A novel intercalation compound of Dion–Jacobson-type perovskite calcium niobate (KCa2Nb3O10) with the nitroxy radical 2,2,6,6-tetramethylpiperidyl-1-oxy (TEMPO) task-special ionic liquid (TEMPO-IL)...

Mineral Phase Crystallization Sequence of Delta Steel Company (DSC), Ovwian-Aladja, Western Niger Delta Steelmaking Slag for Use as Material in Industry

Slag is a non-metallic by-product obtained in the refining of metals from metallic ores. Slag production at the Delta Steel Company (DSC), Ovwian-Aladja, western Niger Delta, follows the direct iron reduction steelmaking process. Fifteen company slag samples collected were examined by x-ray fluorescence, thin section petrography and electron microprobe analyses to establish the mineralogy and mineral crystallization sequence and thus explain their occurrences. The results show the presence of synthesized silicate minerals of belite, melilite and merwinite; calcium aluminate, wustite, periclase, perovskite and glass in the slag formed at between the temperatures of 1500°C and 500°C. Crystallization sequence is alpha (α) form of belite (1500°C-1420°C), alpha high (α/H) belite (1420°C-1160°C), alpha low (α/L) belite (1160°C-680°C, beta (β-) belite (680°C – 630°C), Melilite (1420°C-680°C), aluminate, merwinite, wustite, periclase, peruvskite and glass (630°C–500°C) in that order. This study has revealed that in behavior, synthetic minerals also crystallize from high to low temperature forms as is the case with natural minerals formed from silicate magmas. The forming behaviour of these minerals confers on them the important characteristics for industrial use as an industrial mineral compliment to natural materials.

Trace element composition of silicate inclusions in sub-lithospheric diamonds from the Juina-5 kimberlite: Evidence for diamond growth from slab melts

The trace element compositions of inclusions in sub-lithospheric diamonds from the Juina-5 kimberlite, Brazil, are presented. Literature data for mineral/melt partition coefficients were collated, refitted and employed to interpret inclusion compositions. As part of this process an updated empirical model for predicting the partitioning behaviour of trivalent cations for garnet–melt equilibrium calibrated using data from 73 garnet-melt pairs is presented. High levels of trace element enrichment in inclusions interpreted as former calcium silicate perovskite and majoritic garnet preclude their origin as fragments of an ambient deep mantle assemblage. Inclusions believed to represent former bridgmanite minerals also display a modest degree of enrichment relative to mantle phases. The trace element compositions of ‘NAL’ and ‘CF phase’ minerals are also reported. Negative Eu, Ce, and Y/Ho anomalies alongside depletions of Sr, Hf and Zr in many inclusions are suggestive of formation from a low-degree carbonatitic melt of subducted oceanic crust. Observed enrichments in garnet and ‘calcium perovskite’ inclusions limit depths of melting to less than ~600km, prior to calcium perovskite saturation in subducting assemblages. Less enriched inclusions in sub-lithospheric diamonds from other global localities may represent deeper diamond formation. Modelled source rock compositions that are capable of producing melts in equilibrium with Juina-5 ‘calcium perovskite’ and majorite inclusions are consistent with subducted MORB. Global majorite inclusion compositions suggest a common process is responsible for the formation of many superdeep diamonds, irrespective of geographic locality. Global transition zone inclusion compositions are reproduced by fractional crystallisation from a single parent melt, suggesting that they record the crystallisation sequence and melt evolution during this interaction of slab melts with ambient mantle. All observations are consistent with the previous hypothesis that many superdeep diamonds are created as slab-derived carbonatites interact with peridotitic mantle in the transition zone.

Enhancement of luminescence intensity and spectroscopic analysis of Eu3+-activated and Li+ charge-compensated CaTiO3 color tunable phosphors for solid-state lighting

The present work explores a well-crystallized perovskite calcium titanate (CaTiO3) doped with trivalent europium (Eu3+) and co-doped with lithium ion (Li+) successfully synthesized by a conventional solid-state reaction method, and the impact of single dopant and co-dopant on the photoluminescence performances of the sample has been investigated by emission, excitation and diffuse reflectance spectra at the room temperature. Photoluminescence spectra of Li+-doped CaTiO3:Eu3+ nanophosphor revealed at intense pink emission peak for Ca(0.85−y)Li y TiO3:0.15Eu3+ nanophosphor around wavelength 619 nm in the visible region upon the excitation of near-UV light at wavelength 397 nm due to 5 D 0 → 7 F 2 transition in Eu3+. The incorporation of Li+ ion on CaTiO3:Eu3+ nanophosphors enhanced the emission probability from higher 5 D 0 state to lower 7 F j state, and its PL intensity is found to be three times greater than the intensity of CaTiO3:Eu3+ nanophosphor. The spectral characteristics and the Eu–O ligand behavior were confirmed in light of Judd–Ofelt theory from the Emission spectra rather than absorption spectra. Their crystal structure was confirmed by X-ray diffraction (XRD) which is in good agreement with pure orthorhombic phase with space group Pbnm, and it also indicated that the incorporation of the dopant/co-dopant did not affect the crystal structure. The experimental observation reveals that the developed phosphor material Li+-co-doped CaTiO3:Eu3+ can be used in solid-state lighting devices.

Tuning bipolar resistive switching by forming defect dipoles in A-site-deficient perovskite calcium titanate thin films

If we intentionally make the A-site in an ABO3 perovskite structure deficient, it is possible to tune the resistive switching effect by forming defect dipoles. In this study, an A-site-deficient calcium titanate (Ca0.95TiO3, CTO) thin film was fabricated on a Pt/Ti/SiO2/Si substrate as an active layer for resistive random-access memory. The Pt/CTO/Pt device exhibited stable bipolar resistive switching performance with good endurance and long retention. The resistive switching may be attributable to the formation and rupture of the conduction filaments due to the O vacancies and defect dipoles resulting from the interaction between the Ca and O vacancies.

Porous perovskite calcium–manganese oxide microspheres as an efficient catalyst for rechargeable sodium–oxygen batteries

The porous micro–nanostructured CaMnO3 electrode delivered a high specific capacity, high rate capacity and enhanced cyclability in rechargeable sodium–oxygen batteries.

Characterization and formation of hydroxyapatite on Ti6Al4V coated by plasma electrolytic oxidation

In this study, Ti6Al4V alloy was coated in the solution consisting of calcium acetate (CA) and β-calcium glycerophosphate (β-Ca-GP) by plasma electrolytic oxidation (PEO) to produce hydroxyapatite and calcium apatite-based composite used as of bioactive and biocompatible materials in biomedical applications. The phase structures, surface morphologies, functional groups of molecules, chemical compositions of the surfaces and the binding energies of atoms in the coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Anatase, rutile, calcium oxide, titanium phosphide, whitlockite, tri-calcium phosphate (TCP), perovskite calcium titanate and hydroxyapatite phases on the coating were detected by XRD analysis. The surface of coatings produced by PEO method has a porous structure. The amount of amorphous hydroxyapatite is the highest value for the coating produced at 5min in XPS and ATR-FTIR results, whereas the amount of crystalline hydroxyapatite has the highest value for coating produced at 120min in XRD results.

High-pressure phase transitions and subduction behavior of continental crust at pressure–temperature conditions up to the upper part of the lower mantle

We precisely determined detailed phase relations of upper continental crust (UCC) at 20–28GPa and 1200–1800°C across the 660-km discontinuity conditions with a high-pressure multi-anvil apparatus. We used multi-sample chambers packed with both of UCC and pressure marker, and they were kept simultaneously at the same high-pressure and high-temperature conditions in each run. The high-pressure experiments were carried out in pressure and temperature intervals of about 1GPa and 200°C, respectively. At 22–25GPa and 1600–1800°C, UCC transformed from the assemblage of CaAl4Si2O11-rich phase (CAS)+clinopyroxene+garnet+hollandite+stishovite to that of calcium ferrite+calcium perovskite+hollandite+stishovite via the assemblage of CAS+calcium ferrite+calcium perovskite+garnet+hollandite+stishovite. No CAS was observed at 1200°C. The textures and grain sizes in the run products suggested that hollandite (II) (monoclinic symmetry) was stable above 24–25GPa and transformed to hollandite (I) (tetragonal symmetry) during decompression. We calculated the density of UCC at high pressure and high temperature from the mineral proportions which were calculated from the mineral compositions. UCC has a higher density than PREM up to 23.5GPa in the range of 1200–1800°C. Above 24GPa, the density of UCC is lower than that of PREM at 1600–1800°C, but is almost equal to that at 1400°C and higher than PREM at temperature below 1400°C. Therefore, we suggest that the subducted UCC may penetrate the 660-km discontinuity into the lower mantle, when its temperature is lower than 1400°C at around 660km depth.

Combined Nd and Hf isotope evidence for deep-seated source of Isua lavas

We present the first combined 146,147Sm– 142,143Nd and 176Lu– 176Hf study of mafic rocks (amphibolites) from the western part of the Isua Supracrustal Belt (ISB, SW Greenland). Sm–Nd and Lu–Hf whole-rock isochrons yield identical ages within error: 3.72 ± 0.08 and 3.67 ± 0.07 Ga, respectively. 142Nd measurements confirm and extend the database of 142Nd excesses in Isua samples (μ 142Nd = 7–16 ppm relative to the terrestrial Nd standard), indicating that early-differentiated reservoirs escaped complete homogenization by mantle convection until the Archean. Combined 146,147Sm– 142,143Nd systematics suggest differentiation of the Isua amphibolite reservoir at maximum ages of ~ 4.53, ~ 4.47, and ~ 4.32 Ga. These ages are relative to, respectively, ordinary-chondritic, enstatite-chondritic, and higher-than-chondritic mantle compositions. The intercept of the Sm–Nd whole-rock isochron is in accordance with 142Nd results and consistent with a superchondritic initial 143Nd/ 144Nd ratio (ε 143Nd 3.7Ga = + 1.41 ± 0.98). In contrast, the corresponding initial ε 176Hf 3.7Ga = − 1.41 ± 0.57 is subchondritic. Since Lu/Hf and Sm/Nd fractionate similarly during mantle processes, the Sm–Nd and Lu–Hf isotope systems display incongruent relative parent–daughter behavior in the source of Isua amphibolites. Based on high-pressure and -temperature phase partition coefficients, we propose a model that satisfies 147Sm– 143Nd, 176Lu– 176Hf, and 142Nd results, as well as trace element characteristics. A deep-seated source composed largely of magnesium perovskite (98% MgPv) and containing 2% calcium perovskite satisfactorily explains the Nd and Hf isotopic discordance observed for Isua amphibolites. The negative HFSE anomalies characterizing Isua basalts likewise could have been inherited from such an early (4.53–4.32 Ga) deep mantle cumulate. Since the ~ 4 Ga old Acasta Gneisses (Northwest Territories, Canada) have radiogenic 176Hf/ 177Hf (Scherer et al., 2010), dissociation of the Lu–Hf and Sm–Nd isotope systems may not be a ubiquitous feature of the Hadean mantle, but rather reflects that a deep-seated source was involved in the formation of ISB lavas.

Hydrothermal growth of calcium titanate nanowires from titania

Perovskite calcium titanate (CaTiO3) nanowires with average diameters in the range of 120–130 nm were grown by hydrothermal treatment of commercial anatase-titania (TiO2) and calcium chloride in aqueous sodium hydroxide solution (2.5–13 M). Reactions were carried out in temperature range of 110–150 °C at various pH (9–13) for 12–72 h. The study revealed that these parameters affect the crystal morphology and size of crystallites. Reaction products obtained at different stages were characterized by thermogravimetry (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD analysis revealed the formation of CaTiO3 phases with orthorhombic crystal structure. Thermal analysis results showed that anatase-TiO2 was thermally stable below 400 °C and at higher temperatures anatase transforms to rutile phase whereas CaTiO3 was stable up to 850 °C.

Phase relations and equation of state of a natural MORB: Implications for the density profile of subducted oceanic crust in the Earth's lower mantle

The phase relations and density of a natural mid‐ocean ridge basalt (MORB) were investigated from 28 to 89 GPa and 1600 to 2700 K by in situ X‐ray diffraction measurements and chemical analysis of the quenched samples using transmission electron microscopy (TEM). We observed an assemblage of five phases up to 50 GPa, namely an aluminum‐bearing magnesium perovskite phase, a calcium perovskite phase, a stishovite phase, the new aluminum‐rich (NAL) phase, and a calcium ferrite‐type phase. The NAL phase was no longer observed above 50 GPa. The phase proportions were obtained by Rietveld refinement of the in situ X‐ray diffraction patterns. After the disappearance of the NAL phase beyond 50 GPa, the proportion of each phase remains constant up to 89 GPa. The density of MORB was calculated using the measured volumes, phase proportions, and chemical compositions of the coexisting phases. The thermoelastic parameters of the MORB sample were estimated from the fit of the measured densities at various pressure and temperature conditions. Resulting MORB density profiles were calculated for different subducting slab temperature profiles. MORB densities are 0.5% to 2% greater than those of the surrounding mantle over the entire lower mantle range, suggesting MORB likely subducts to the core–mantle boundary.

The nature of the boundary between the upper and the lower mantle and its influence on convection

In the PREM seismic model, the boundary between the upper and the lower mantle is accepted at a depth of 670 km, where seismic velocities and density increase. However, until recently there was an obvious inconsistency in this model. The density increases abruptly, and the velocities, in addition to the jumps, have also the subsequent zones of increased gradient. The discontinuity between the upper and the lower mantle is related to the transition of olivine from the ringwoodite phase into the mixture of perovskite and magnesiowustite. However, in the pyrolyte model, the transition zone of the upper mantle consists not wholly of olivine, but partly of olivine (60%) and partly of garnet (40%). The latest data of the garnet measurement at high pressures show that it also experiences phase transition, being converted into magnesium perovskite with the impurity of calcium perovskite. In contrast to the sharp transition in olivine (within a depth interval of only 5 km), the transition in garnet is spread over the interval of depths of 660–710 km. In the widely used PREM and AK135 models, this additional transition corresponds to the zone of the increased gradient in seismic velocities, while in the density distribution it is included in the sharp transition of ringwoodite. Thus, the mineralogy data indicate the need for correction of the PREM and AK135 seismic models: the density jump at a depth of 660 km should be reduced by approximately a factor of two, and a subjacent layer with the increased density gradient should be added at the depth interval of 660–710 km. The phase transition in olivine hampers the mantle flows, although in garnet it accelerates them. Therefore, with an allowance for the smaller jump in density, the decelerating effect of the subducting plates, caused by the phase transition in olivine, decreases, and, furthermore, the effect of their acceleration, caused by the phase transition in garnet, is added. The decrease in the density jump by almost a factor of two will lead to essential changes in the results of the majority of recent works addressing the assessment of the deceleration of convection at the upper/lower mantle discontinuity on the basis of the PREM model.

Experimentally dictated stability of carbonated oceanic crust to moderately great depths in the Earth: Results from the solidus determination in the system CaO‐MgO‐Al2O3‐SiO2‐CO2

Solidus melting phase relations are reported for carbonated eclogite in the system CaO‐MgO‐Al2O3‐SiO2‐CO2 at 12 to 25 GPa. From 12 to 16 GPa, melts are in equilibrium with clinopyroxene, stishovite, garnet, aragonite, and magnesite. At 20 and 25 GPa, melts are in equilibrium with garnet, stishovite, calcium‐alumino silicate, calcium perovskite, and magnesite. Melting reactions demonstrate that from 12 to 16 GPa, stishovite is in reaction with the melt. At 20 and 25 GPa, garnet and stishovite together are produced upon melting of model, carbonated eclogite. At 20 and 25 GPa, calcium perovskite is also the phase that contributes the most toward liquid production. Melt compositions at all pressures are carbonatitic, with roughly 37–40 wt% dissolved CO2. From 12 to 16 GPa, the liquids are calciocarbonatites with Ca#molar of ∼69–71; liquid compositions become less calcic with Ca# of ∼52–55 at 20 and 25 GPa. Given these melting phase relations, suitable subduction zone adiabats do not intersect the solidus of model carbonated eclogite at depths investigated in the present study. Hence, on this basis, it is fair to say that carbonated eclogite possibly avoids melting in subduction zone settings, thereby delivering carbonate to at least moderate depths in the Earth. However, owing to local heating events, small‐degree melting of carbonated eclogite is not completely precluded, and the liquids liberated from this melting can be viewed as agents of chemical mass transfer in the deep Earth. At present, however, geochemical consequences of subduction‐related melting of carbonated eclogite are difficult to evaluate.

Infrared thermochromic behaviour of a compositeSm0.65Ca0.35MnO3–poly(styrene-co-acrylonitrile) film

Samarium calcium perovskite manganiteSm0.65Ca0.35MnO3 was dispersed homogeneously in a solution of poly(styrene-co-acrylonitrile). A thin filmwas deposited on (100) oriented silicon substrate by spin-coating and the opticalthermochromic behaviour in the infrared range was studied. In the wavelength range 8–14 µm, the optical transmittance of the thermochromic composite coating exhibited a largevariation between 173 and 343 K due to a semiconductor–metal first-order transition atTc = 250 K. The thermochromic behaviour of the composite coatings was optimized. The contrast inthe transmittance first increased with pigment content, then reached a maximumvalue.

Phase transition zone width implications for convection structure

In the Ringwood pyrolitic (pyroxene‐olivine) model, the upper mantle consists of peridotite (90%) and eclogite (10%). Peridotite includes olivine (60%), orthopyroxene (25%), clinopyroxene, and garnet. Eclogite contains clinopyroxene (60%), garnet (30%), and other minor admixtures. The lower mantle consists of silicate perovskite (Mg 0.9 Fe 0.1 )SiO 3 (75%), magnesiowustite (Mg 0.8 Fe 0.2 )O (15%), and calcium perovskite (CaSi)O 3 (10%) [Davies, 1999]. With an increase in pressure and temperature, the mantle material experiences phase transitions. Since it has a multicomponent composition, the transition does not occur in a jumpwise manner but is distributed over an interval of pressures ∆ p or depths d = ∆ p /( ρ g ) . At a depth of 410 km, olivine is transformed into wadsleyite with a density jump of δρ / ρ 0 = 0.07 at a phase equilibrium curve slope of γ = dp / dT = 1.6‐3.0 MPa/K; the width of the phase transition zone is d = 13 km. At a depth of 520‐580 km, wadsleyite is transformed into

Developments on Susceptibility and Magnetization Measurements under High Hydrostatic Pressure

New techniques using Moissanite and diamond anvil cells have allowed us to measure the ac susceptibility and dc magnetization of different strongly correlated systems at high hydrostatic pressures. We present here a new type of anvil cell designed to go inside a SQUID magnetometer, specifically the MPMS system of Quantum Design. This cell is capable of reaching over 100 kbar of pressure. Using this technique in conjunction with our previously reported technique for susceptibility measurements in an anvil cell, we have studied the ferromagnetic phases of the 3-dimensional itinerant ferromagnet cobalt disulphide, CoS 2 , as well as 2-dimensional layered perovskite calcium ruthenate, Ca 2 RuO 4 .

Microwave synthesis of calcium bismuth niobate thin films obtained by the polymeric precursor method

The crystal structure, surface morphology and electrical properties of layered perovskite calcium bismuth niobate thin films (CaBi 2Nb 2O 9-CBN) deposited on platinum coated silicon substrates by the polymeric precursor method have been investigated. The films were crystallized in a domestic microwave and in a conventional furnace. X-ray diffraction and atomic force microscopy analysis confirms that the crystallinity and morphology of the films are affected by the different annealing routes. Ferroelectric properties of the films were determined with remanent polarization P r and a drive voltage V c of 4.2 μC/cm 2 and 1.7 V for the film annealed in the conventional furnace and 1.0 μC/cm 2 and 4.0 V for the film annealed in microwave furnace, respectively. A slight decay after 10 8 polarization cycles was observed for the films annealed in the microwave furnace indicating a reduction of the domain wall mobility after interaction of the microwave energy with the bottom electrode.

Compressibility of the calcium aluminosilicate, CAS, phase to 44 GPa

In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch–Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of ρ 0 = 3.888 g/cm 3 and a bulk modulus of K 0 = 229 ± 9 GPa for K ′ 0 = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at K ′ 0 = 4, then the value of K 0 = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase.

Limits to resolution in composition and density in ultra high-pressure experiments on natural mantle-rock samples

We compressed and analyzed an undepleted natural peridotite—thought to be representative of the Earth’s upper mantle—from ∼25 to 110 GPa and heated to 2000–2500 K. Scatter in zero-pressure unit-cell volumes observed for high-pressure phases synthesized from peridotite, of ±0.4% for orthorhombic perovskite and ±0.8% for magnesiowüstite, can be ascribed to compositional heterogeneity in the natural starting material and its transformation products (calcium perovskite was also observed at high pressures, but does not quench to zero pressure). The scatter is larger than the measurement uncertainties, which are as little as ±0.1%, but is less than would be expected from the variation in composition among distinct minerals if the starting material had failed to equilibrate upon transformation to the high-pressure assemblage (e.g., up to ±0.6–0.8% in volume for orthorhombic perovskite). The equilibrium unit-cell volume of orthorhombic perovskite calculated from an average of electron microprobe analyses on the quenched samples, 163.3 (±0.6) Å 3 , agrees to within 0.4% with the average value measured from the same samples by X-ray diffraction at zero pressure (163.9±0.7 Å 3 ). Similarly, values of zero-pressure density for the whole-rock assemblage of high-pressure phases are identical (4.13±0.03 g/cm 3 ), whether derived from electron microprobe or X-ray diffraction measurements.