Separation and purification of tantalum from plumbomicrolite of amazonite deposit in Kola Peninsula by acid leaching and solvent extraction

A plumbomicrolite concentrate(PMC)was leached with the mixture of HF and H2SO4,HF and HNO3 acids,respectively.Optimal conditions ensuring high recovery of tantalum and niobium(up to 99%)into solution,and radionuclides into insoluble residue were determined.Fluoride-sulfuric acid and fluoride-nitric acid schemes were proposed for PMC leaching by an extractive separation of tantalum form niobium,lead and impurities,and production of high-purity tantalum compounds.Octanol-1 was used as an extractant.Optimal conditions for production of high-purity tantalum strip solutions were defined for all stages(extraction-scrubbing-stripping).Produced tantalum compounds,such as tantalum pentoxide and potassium heptafluotanthalate,comply with the norms for high-purity substances in terms of impurities content.Final choice of the PMC processing scheme is determined by its profitability.

Characterization of amphiboles from the Kola super-deep borehole, Russia by Raman and infrared spectroscopy

We present here for the first time,the Raman and infrared spectroscopic investigation of amphiboles from the World's deepest borehole,the Kola super-deep borehole,at the depth of 11.66 km.The Kola Super-deep borehole(SG-3)(henceforth referred as KSDB)is located in the northwest of the Kola Peninsula in the northern frame of the Pechenga structure,Russia.It was drilled in the north-eastern part of the Baltic Shield(69о5’N,30о44’E)and reached a depth of 12.262 km.It has been drilled in the northern limb of the Pechenga geosyncline composed of rhythmically inter-bedded volcanogenic and tuffaceous-sedimentary strata extending to the NW at 300°–310°and dipping to SW at angles of 30°–50°.The SG-3 geological section is represented by two complexes–Proterozoic and Archaean.Amphibolite facies is dominant in the depth region from 6000 m to 12,000m to the deepest.The Raman spectra of the sample reveal abundant presence of plagioclase and amphiboles.The most distinct Raman peak in this study indicates the tremolite-ferro-actinolite rich enrichment of the borehole samples at this depth corroborating earlier conventional petrographic studies.

Mining-Induced Seismicity in the Kola Peninsula Mines

Mining-induced seismicity is a reflection of rock geomechanical evolution of geological environment in the natural and man-made systems and in the mining-technical systems. In order to predict and prevent mining-induced seismicity, it is necessary to research geodynamics and stress state of intact rock mass, to determine possible deformations and additional stresses as a result of large-scale rock extraction, conditions of accumulated energy release. For that a geodynamical monitoring is required on every stage of deposit development and a closing. The report considers principal influencing factors of preparation and occurrence of mining-induced earthquakes. Also it estimates precursors and indicators of rock mass breaking point, and experience concerning prediction and prevention of mining-induced seismicity in the Khibiny apatite mines in the Murmansk region, which is the largest mining province.

磷酸钛离子交换剂纯化饱和LiNO_(3)溶液的平衡

研究磷酸钛离子交换剂(Li-TiOP)在饱和LiNO_(3)溶液中对Cu^(2+)、Co^(2+)、Mn^(2+)、Ni^(2+)和Cr^(3+)离子的吸附性能。采用XRD、SEM、TG、DSC、NGSP和元素分析对固体样品进行表征。采用原子吸收光谱法(AAS)和电感耦合等离子体质谱法(ICP MS)测定溶液中离子的浓度。采用Langmuir、Freundlich、Temkin和Nikolsky模型计算金属离子的吸附等温线。在研究金属离子吸附时,必须考虑吸附剂的溶剂化状态。Li-TiOP对所研究离子的选择性为:Cr^(3+)>Cu^(2+)>Mn^(2+)>Co^(2+)>Ni^(2+),且对上述4种模型均适用。吸附过程热力学参数的变化与吸附剂离子电位的变化有关。磷酸钛能有效去除多组分溶液中的微量金属离子,使LiNO_(3)纯度高于99.999%(质量分数)。

Mechanism and kinetics of iron extraction from high silica boehmite−kaolinite bauxite by hydrochloric acid leaching

The chemical and mineral compositions of bauxite recovered from the Severoonezhsk Bauxite Mine(Arkhangelsk region,Russia)were studied by XRD,ICP-OES,TG/DSC,SEM,TEM,and Mössbauer spectroscopy.The iron-containing minerals of the bauxites were found to comprise alumogoethite(α-Fe_(1−x)Al_(x)OOH),alumohematite(α-(Fe_(1−x)Al_(x))_(2)O_(3)),alumoakaganeite(β-Fe_(1−x)Al_(x)O(OH,Cl)),and chromite(FeCr_(2)O_(4)).The efficiency of Fe extraction from the bauxite by HCl leaching was 82.5%at 100℃,HCl concentration of 10%,solid/liquid ratio of 1:10,and the process duration of 60 min,with aluminum loss from the bauxites below 4.5%of the total Al contents in the bauxite.Analysis of the kinetics of the iron leaching process proved diffusion to be the limiting stage of the process at 90−100℃.Bauxite residue after leaching presented traces of α-Fe_(1−x)Al_(x)OOH and β-Fe_(1−x)Al_(x)O(OH,Cl),and most of the iron content was in the FeCr_(2)O_(4).In bauxite residue after HCl leaching,in addition to iron oxide,the contents of chromium and calcium oxides significantly decreased.The iron chloride liquor after leaching contained the rare earth elements(REE)of 6.8 mg/L Sc,4.1 mg/L Ce and 2.3 mg/L Ga.

Data-Driven Discovery in Mineralogy: Recent Advances in Data Resources, Analysis, and Visualization

Large and growing data resources on the diversity, distribution, and properties of minerals are ushering in a new era of data-driven discovery in mineralogy. The most comprehensive international mineral database is the IMA database, which includes information on more than 5400 approved mineral species and their properties, and the mindat.org data source, which contains more than 1 million species/locality data on minerals found at more than 300 000 localities. Analysis and visualization of these data with diverse techniques—including chord diagrams, cluster diagrams, Klee diagrams, skyline diagrams, and varied methods of network analysis—are leading to a greater understanding of the co-evolving geosphere and biosphere. New data-driven approaches include mineral evolution, mineral ecology, and mineral network analysis—methods that collectively consider the distribution and diversity of minerals through space and time. These strategies are fostering a deeper understanding of mineral co-occurrences and, for the first time, facilitating predictions of mineral species that occur on Earth but have yet to be discovered and described.

Baddeleyite from Large Complex Deposits: Significance for Archean-Paleozoic Plume Processes in the Arctic Region (NE Fennoscandian Shield) Based on U-Pb (ID-TIMS) and LA-ICP-MS Data

Baddeleyite is an important mineral geochronometer. It is valued in the U-Pb (ID-TIMS) geochronology more than zircon because of its magmatic origin, while zircon can be metamorphic, hydrothermal or occur as xenocrysts. Detailed mineralogical (BSE, KL, etc.) research of baddeleyite started in the Fennoscandian Shield in the 1990s. The mineral was first extracted from the Paleozoic Kovdor deposit, the second-biggest baddeleyite deposit in the world after Phalaborwa (2.1 Ga), South Africa. The mineral was successfully introduced into the U-Pb systematics. This study provides new U-Pb and LA-ICP-MS data on Archean Ti-Mgt and BIF deposits, Paleoproterozoic layered PGE intrusions with Pt-Pd and Cu-Ni reefs and Paleozoic complex deposits (baddeleyite, apatite, foscorite ores, etc.) in the NE Fennoscandian Shield. Data on concentrations of REE in baddeleyite and temperature of the U-Pb systematics closure are also provided. It is shown that baddeleyite plays an important role in the geological history of the Earth, in particular, in the break-up of supercontinents.

Permo–Triassic and Liassic Tethyan Oceanic Tracts within the Pontide Belt Along the Southern Margin of Eurasia, Northern Anatolia

The Pontide belt in northern Turkey includes three major tectonic terranes,the Strandja Massif（Sj M）,and the Istanbul（ISZ）and Sakarya Zones（SZ）(Fig.1).We present new age and geochemical data from ophiolites and ophiolitic mélanges within the Sakarya Zone and show that these mafic–ultramafic rocks are the remnants of Tethyan oceanic lithosphere formed in different tectonic settings.The main ophiolite occurrences investigated in this study along the Karakaya Suture（KS）are associated with the latest Triassic Cimmeride orogeny,and in the Küre–Yusufeli ophiolite belt are part of the Alpide orogeny.The Karakaya Suture Zone ophiolites in northern west Turkey are comprised mainly of the Denizgoren（?anakkale）ophiolite,Bo?azk?y（Bursa）,Geyve（Sakarya）,Almac?k（Düzce）and?ele（Bolu）metaophiolites.The Denizg?ren ophiolite largely contains upper mantle peridotites,which are equivalents of the Permo–Triassic Lesvos peridotites and mélange units farther SW in the northern Aegean Sea.The Bo?azk?y ophiolite includes serpentinite and metagabbro,and the Almac?k and Geyve ophiolites display an almost complete Penrose–type sequence consisting of serpentinizeduppermantleperidotites,cumulate ultramafic–mafic rocks,isotropic gabbros,dolerite and plagiogranite dikes,and extrusive rocks.U–Pb zircon dating of plagiogranite dikes from?ele has revealed an igneous age of 260 Ma,and 255,235,227 Ma from Almac?k（Bozkurt et al.,2012a,b）.Consistent with the previouslypublished Permo–Triassic age,we obtained a 268.4±6.3 Ma U–Pb zircon age from a plagiogranite dike within the Almacik ophiolite to the west.This KS ophiolite belt containing the?ele,Almac?k,Geyve ophiolites within the SZ extends westward into the Armutlu Peninsula and then into the Biga Peninsula（i.e.Denizg?ren ophiolite）and most likely connects with the remnants of the Triassic Meliata–Meliac ocean basin（Stampfli and Borel,2002）in the Balkan Peninsula.The KS ophiolites also continue eastward within the Pontide Belt into the Elekda?ophiolite（eastern Kastamonu）and then to the Refahiye ophiolite in NE Anatolia.Triassic granites in the SZ represent a magmatic arc that formed as a result of the northward subduction of the Izmir–Ankara–Erzincan oceanic lithosphere existing during the late Paleozoic through Cretaceous（Sarifakioglu et al.,2014）beneath the Pontides.We obtained a U–Pb zircon age of 231±2 Ma from a metagranitic intrusion into the Variscan basement of the SZ in the Kastamonu region of the central Pontides.This metagranite is enriched in LILE（Rb:63 ppm;Ba:65 ppm;Sr:200 ppm）and depleted in HFSE（Y:12.58 ppm;Yb:1.26 ppm;Ti O2:0.2 wt.%;Nb:7.6 ppm;Hf:3.9 ppm）,characterizing it as subduction–related calc-alkaline pluton.Lead（3.9 ppm）,U（1.6 ppm）and Ce（59 ppm）contents are interpreted as evidence for contamination by continental crust.The Küre basin to the north opened during the late Triassic to Liassic,following a backarc rifting episode in the central Pontides.Metabasic dike intrusions in the Devrekani metamorphic massif represent the first magmatic stage of this backarc rifting event.Whole-rock 40Ar-39Ar dating ofthe metabasic dikes has yielded cooling ages of 160.5±1.2 Ma. We infer that this age was reset due to thermal heating during the emplacement of the Middle Jurassic granitoids as the Küre oceanic basin was closing. The Küre ophiolite contains upper mantle peridotites and oceanic crustal rocks composed mainly of pillow–massive–breccia basalts, dacitic and rhyolitic lavas–tuffs, diabase dyke swarms, massive gabbros and a limited extent mafic cumulates. We obtained 182.6±1.9 Ma as a whole-rock 40Ar-39 Ar age from a pillow basalt and a U–Pb zircon age of 171±1 Ma from the granitic intrusion cross-cutting the peridotites. The easternmost representatives of the Küre ophiolite occur in the Yusufeli（Artvin） area in the eastern part of the Pontide belt. Here, oceanic crustal rocks are tectonically related to metamorphic rocks of the Variscan basement of the SZ. The ophiolitic crustal rocks contain isotropic gabbro and mafic and felsic dikes. Serpentinized upper mantle peridotites are scarce. Pillow lava basalts are overlain by a thick metasandstone–metashale association with locally foliated meta–lava and some manganiferous chert and mudstone interlayers. We obtained a U–Pb zircon age of 172.5±1.4 Ma from the granitic intrusion cross-cutting the Yusufeli ophiolite and of 181.9±0.9 Ma from a felsic dike（plagiogranite） in the Yusufeli ophiolite. The Middle Jurassic granites are related to the closure of the Küre-Yusufeli marginal ocean basin. The Küre and Yusufeli ophiolites have been previously interpreted as the remnants of the Paleotethys or the Intra-Pontide Ocean. However, we posit that these ophiolites represent amarginal, short-lived（;0 Ma） ocean basin, which opened during the late Triassic through Liassic, and then closed in Dogger. This oceanic lithosphere is similar to the Evros ophiolite in the northeastern Greece in terms of its ages and geochemical characteristics.

Bioremediation of Oil-Polluted Cultivated Soils in the Euro-Arctic Region

It has been studied restoration processes in oil products-polluted soils at high northern latitudes （the Murmansk region, Russia）. Mineral and organic fertilizers and a bacterial preparation （based on the local strains of hydrocarbon-oxidizing bacteria） were applied for restore polluted soils. Periods of removing OP （oil products） from soil were determined by the reduction of the pollutant concentration and by soil biological activities--the dynamics of bacteria number and CO2 emission from soil. The soil OP even at such a high concentration （as 10 L/m^2） had stimulated bacterial reproduction. In three summer month levels in the control variant without ameliorators of OP content decreased by 59% from the initial level, in the variant with mineral and organic fertilizers by 86%, in the variant with the bacterial preparation by 84%. Stimulating of indigenous microorganisms activity with additional nutrients was no less effective technique of OP-polluted soil bioremediation, than applying the bacterial preparation, which requires considerable financial investment. Moderately contaminated of OP soil is a source of additional carbon dioxide emission in the atmosphere. Pollution soil with OP caused for increasing of share of potentially pathogenic fungi in the fungal community.

Archean of Greenland and Fennoscandia

The North Atlantic craton in southern West Greenland mainly consists of a tectonic collage of Mesoarchean continental crustal terranes, which were amalgamated at c. 2.7 Ga and are currently exposed at mid-crustal amphibolite to granulite facies levels. Tonalitic orthogneisses predominate, intercalated with slightly older tholeiitic to andesitic metavolcanic rocks and associated gabbro-anorthosite intrusive complexes. The North Atlantic craton also contains enclaves of Eoarchean, c. 3.86-3.6 Ga orthogneisses and supracrustal rocks including the Isua greenstone （or supracrustal） belt. This is the oldest known assemblage of rocks deposited at the surface of the Earth, comprising mafic pillow lavas, banded iron formations and metasedimentary schists with local disseminated graphite of possible biogenic origin. Eoarchean rocks have not been found in Kola and Karelia in Fennoscandia where most rocks are 2.9-2.7 Ga tonalitic-trondhjemitic-granodioritic orthogneisses with intercalated coeval greenstone belts and amphibolites. Mesoarchean 3.0-3.2 Ga rocks are found in the eastern and western parts of the Karelian province. Subduction-related rocks like the Iringora supra-subduction type ophiolite and basalt-andesite-dacite-rhyolite series volcanic rocks in many greenstone belts, as well as eclogites are found in the Archean of Fennoscandia. A clear distinction between Greenland and Fennoscandia is the abundance of 2.75-2.65 Ga igneous rocks in Fennoscandia which indicates that these two cratons had a separate evolution during the Neoarchean.

Economic Consequences of Tahoku Earthquake of March 11, 2011 in Japan

The paper considers the economic consequences of Tahoku earthquake occurred on March 11,2011 at 5：46：23 （UT） at the distance of 70 km from the northeast shore of Japanese coast Honshu. This earthquake had a magnitude of 9 and became the strongest in the whole history of the seismological observations in this part of the planet. The generated tsunami killed more than 15,700 people, damaged 332,395 buildings and 2,126 roads. The total economic loss in Japan was estimated at $309 billion. The catastrophe in Japan also impacted global economy. To reveal its impact, the authors used regional and global stock indexes, production indexes, stock prices of the main Japanese, European and US companies, and import/export dynamics. The authors demonstrated that the catastrophe substantially affected the markets and on the short run in some indicators it exceeded the effect of the global financial crisis. The authors concluded that it is necessary to treat possible strong earthquakes in different regions of the world as one very important factor that can affect the world economy.

License to Mine: A Comparison of the Scope of the Environmental Assessment in Sweden, Finland and Russia

The regulatory framework for mining operations is complex;the licensing process in particular typically involves several laws and a number of permits. This paper assumes that the regulatory framework is strongly influenced by the institutional framework of which it is part, and that it suffers from an institutional path dependence that may decrease the efficiency of the system as well as act barrier to the implementation of necessary environmental requirements. The paper provides: 1) a legal analysis of the regulatory framework governing mining operations in Sweden, Finland and Russia;and 2) a comparative analysis of the scope of the environmental assessment within the licensing process in the examined countries. The result of the analysis of the regulatory frameworks shows great similarity between the Swedish and the Finnish systems, both in terms of the overall structure and the implementation of substantive environmental rules. The Russian system differs in this respect, with more declarative rules and seemingly less substantive assessments. The results also indicate that the regulatory frameworks in all three countries show signs of institutional path dependence, but in very different degrees. Though Russia has indeed implemented major changes in the formal structure, very little has changed in practice. The Swedish regulatory framework for mining shows a deficient systematics and conflicting objectives, despite the implementation of a comprehensive environmental legislation. The recently reformed Finnish system seems to have a more holistic approach.

Effect of sodium injection rate in reduction process on characteristics of tantalum powders

The paper presents a research the effect of sodium injection rate in a melt containing potassium tantalum fluoride and a flux on morphology and characteristics of tantalum powders obtained by sodium reduction.

U-Pb dating of bastnäsite from the Vuoriyarvi massif:An example application for assessing the REE potential of carbonatite-related deposits

The Vuoriyarvi massif is a Devonian multistage alkaline-ultrabasic carbonatite complex within the Kola alkaline province.Dolomite carbonatites of the Vuoriyarvi massif contain abundant rare-earth mineralization mainly represented by ancylite-(Ce)and bastnäsite-(Ce).Ancylite was previously shown to have probably formed in the Devonian(ca.365 Ma)during an early postmagmatic overprint.Previous geological observations have revealed a much later crystallization of bastnäsite but have not been able to specify the exact age of the mineralization.The in situ U-Pb dating of bastnäsite allowed us to constrain its genesis.Bastnäsite for this study was extracted from two varieties of dolomite carbonatite breccias cemented by(1)quartz-bastnäsite and(2)strontianite aggregates(hereafter bastnäsite-rich and strontianite-rich carbonatites–BRC and SRC,respectively).The obtained age estimations(237.7±9.8 Ma and 239.9±4.1 Ma,respectively)indicate that both studied rocks were formed during a single event.The revealed age difference(~125 Ma)excludes the genetic link between the bastnäsite origin and regional alkaline magmatism,pointing out an additional source for the Vuoriyarvi bastnäsite-bearing rocks.Moreover,the obtained U-Pb ages provide strong evidence that a Triassic event is responsible for the occurrence of bastnäsite mineralization due to hydrothermal REE redistribution from the Devonian ancylite-rich carbonatites.Most of the REEs released during this process via dissolution of ancylite were precipitated in situ as bastnäsite,while strontium was transported and incorporated into strontianite.The Pb isotopic characteristics of bastnäsite(^(206)Pb/^(204)Pb=18.1±0.1,^(207)Pb/^(204)Pb=15.3±0.1,and^(207)Pb/^(206)Pb=0.84±0.01)are most probably inherited from the Devonian host rocks of the Vuoriyarvi massif involved in the Triassic overprint.Isotopic signatures of Pb,Sr,and Nd show that the depleted mantle and lower crust played the leading role in formation of the Vuoriyarvi alkaline complex.Taken together,the results of the present study negate the supergene origin of the Vuoriyarvi bastnäsite,implying that the bastnäsite mineralization is not confined to near-surface layers and,therefore,may be dispersed more broadly throughout the complex.These findings raise the question on underestimation of the probable REE reserves and lay the groundwork for a reassessment of the economic potential of the Vuoriyarvi complex.

Photoluminescence,structural and antibacterial properties of co-dopedβ-Ca_(3)(PO_(4))_(2)-type phosphates Ca_(8)CuRE(PO_(4))_(7)(RE=Eu-Er)

Novel Ca_(8)CuRE(PO_(4))_(7)where RE^(3+)=Eu^(3+),Tb^(3+),Dy^(3+),Ho^(3+)and Er^(3+)were synthesized by a solid-state method in air.The structures of the samples were characterized by powder X-ray diffraction using Rietveld refinement to determine the occupation of crystal sites.The samples are found to have a centrosymmetric structure with space group R3c,as shown by dielectric measurements.These synthesized Ca_(8)CuRE(PO_(4))_(7)samples have multifunctional properties.The Cu^(2+)ions provide antibacterial properties,while the rare earth elements ions exhibit luminescence properties,and theβ-Ca_3(PO_(4))_(2)-type host is biocompatible.The photoluminescence properties of RE^(3+)ions were studied and compared with other simmilar Ca_(8)MRE(PO_(4))_(7)phosphates,where M is a divalent metal.The photoluminescence intensity quenching in terms of energy transfer from RE^(3+)to Cu^(2+)is disscused.The bioactive properties were studied in relation to antibacterial activity against E.coli and S.aureus.All syntesized Ca_(8)CuRE(PO_(4))_(7)samples demonstrate very high and stable inhibition of bacteria growth.The correlation between crystal structure and properties is discussed.By combining multiple approaches to the directio nal design of such materials,several important properties within a single chemical compound to achieve biovisualization and bioactive properties simultaneously can be combined.

Telluric iron assemblages as a source of prebiotic phosphorus on the early Earth:Insights from Disko Island,Greenland

Phosphorus is one of the key elements,which determined the emergence of primordial life on our planet.The source of prebiotic phosphorus was most likely to be easily soluble compounds containing phosphorus in the negative form of oxidation(e.g.,phosphides).The present paper is the first thorough investigation of phosphide-bearing mineral assemblages confined to telluric(terrestrial)native iron from volcanic rocks of Disko Island,Greenland.Phosphorus speciation in given assemblages varies from the solid solution in native iron(up to 0.3 wt.%P),different phosphides–schreibersite Fe_(3)P,nickelphosphide Ni_(3)P,barringerite Fe_(2)P,and phosphates,including fluorapatite,anhydrous Fe-Na phosphates,phosphoran olivine and pyroxene(up to 1 wt.%P).The diversity of observed phosphorus speciation can be explained by the steep changes of redox conditions during subsurface crystallization of iron-phosphide-bearing lavas.Based on the available data on likely redox conditions on the early Earth,we hypothesize that reactive prebiotic phosphorus may have originated from shallow crustal rocks.

Comparison of extraction abilities of deep eutectic solvents and aqueous acid solutions for extraction of rare earths and transition metals

In recent years,deep eutectic solvents have attracted increasing interest as effective extractants for the separation of both organic substances and metals from various objects.Acid-based deep eutectic solvents are most often used as extractants for the extraction of metals.In this work,for the first time,the extraction efficiency of transition metals and rare earth elements(Y,Zr,Nb,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Hf and Ta)from mining tailings and Na,K,Ca,Mg,Cu,Fe,Mn,Pb,Ba,Ni and Sr from biodiesel samples using acidic deep eutectic solvents and saturated aqueous solutions of the same acids(malonic,malic,tartaric and citric)is compared.For this,deep eutectic solvents based on acids and their aqueous saturated solutions were prepared and studied.The prepared mixtures were analyzed by IR spectroscopy to confirm the formation of eutectic solvents.Properties such as the density and viscosity of the resulting mixtures were also investigated,as this can be of key importance for the efficiency of metal extraction.The extraction of rare earth metals from mining tailings took a long time(up to several days),while the extraction of metals from fuel took no more than 30 min.Atomic emission spectral methods were used as an analysis method.It is shown that the extraction efficiency with aqueous solutions is better than that with eutectic solvents,which casts doubt on the need for deep eutectic solvents use in this area.

Effective regulation of electronic structures and luminescence properties of LiGd_(9)(SiO_(4))6-x(GeO_(4))xO_(2):Dy^(3+)phosphors by tetrahedral substitution

A series of Dy^(3+)-activated phosphors with the general formula LiGd_(9)(SiO_(4))6-x(GeO_(4))xO_(2):Dy^(3+)(0≤x≤3)characterized by an apatite-type structure were successfully synthesized via a simple solid-state technique involving a partial substitution of[SiO_(4)]^(4-)with[GeO_(4)]^(4-)species.The effects of homovalent[GeO_(4)]^(4-)-[SiO_(4)]^(4-)substitution on the crystal structure,electronic structure,luminescence properties and thermal performance of LiGd_(9)(SiO_(4))6-x(GeO_(4))xO_(2):Dy^(3+)phosphors were studied in details.The phases and microstructure were performed by using X-ray diffraction(XRD)Rietveld refinement method and scanning electron microscopy(SEM)characterization.The substitution of smaller[SiO_(4)]^(4-)ions by larger[GeO_(4)]^(4-)ones makes their unit cell parameters increase gradually,and their band gaps decrease.The photoluminescence spectra of LiGd_(9)(SiO_(4))6-x(GeO_(4))xO_(2):Dy^(3+)(0≤x≤3)exhibit obvious emission peaks located at 477,573 and 675 nm within a visible wavelength region,resulting in an excellent white light.Furthermore,the I573nm/I477nm values of LiGd_(9)(SiO_(4))6-x(GeO_(4))xO_(2):Dy^(3+)(0≤x≤3)become larger with the partial substitution of[SiO_(4)]^(4-)by[GeO_(4)]^(4-),and their CIE chromaticity coordinates exhibit a yellow shift.

Structure and luminescence properties of color-tunable phosphor Sr_(2)La_(3)(SiO_(4))_(3)F:Tb^(3+),Sm^(3+)

A series of single-phase and color-tunable phosphors Sr_(2)La_(3)(SiO_(4))_(3)F:0.15Tb^(3+),xSm^(3+)(SLSOF:0.15Tb^(3+),xSm^(3+)) was prepared using solid-state route.The X-ray diffraction(XRD) was used to characterize the phase of the as-prepared samples.The synthesized phosphors have apatite-type structure without other impurities.Sm^(3+) and Tb^(3+) ions substitute La^(3+) into the lattice and form a single-phase solid solution.The elements are evenly distributed in the sample according to the scanning electron microscopy(SEM) results.The crystal structure of the host phosphor was refined by the Rietveld method.The optical properties were studied in detail by investigation of the luminescence and diffuse spectra,fluorescence decay curves and energy transfer efficiency.The phosphor color can be changed from green(0.29,0.48) to yellow/orange and red(0.57,0.42) via adjusting the doping ratio of Sm^(3+).The SLSOF:0.15Tb^(3+),xSm^(3+)phosphors can emit typical multicolor light such as green,yellow,orange and red with gradually increasing Sm^(3+)doping concentration.All results indicate the occurrence of the energy transfer which results in the color-tunable properties of the phosphors.

CaAl_(2)Si_(2)O_(8) polymorphs:Sensitive geothermometers and geospeedometers

Plagioclase is the major rock-forming mineral constituting the Earth's crust,whereas anorthite(CaAl_(2)Si_(2)O_(8))is a common minerals in lunar highlands crust,meteorites,possibly in some comets and on Mercury.Besides anorthite,two high-temperature polymorphs of CaAl_(2)Si_(2)O_(8)are known:dmisteinbergite and svyatoslavite,which are found in burnt coal dumps,meteorites and pseudotachylytes.Here we present the results of detailed studies(quenching experiments,elemental analysis,Raman spectroscopy and in situ high temperature single crystal X-ray diffraction(up to 1000℃))on naturally co-occurring CaAl_(2)Si_(2)O_(8)polymorphs(anorthite,dmisteinbergite and svyatoslavite)from a burnt coal dump in Kopeisk,Russia.New polymorphs were found in all natural samples and obtained upon heating of dmisteinbergite(unquenchableβ-dmisteinbergite and quenchable y-dmisteinbergite).It was shown that Ca coordination differs significantly in CaAl_(2)Si_(2)O_(8)polymorphs,resulting in a different capacity to host Ba and possibly other large ion lithophile elements.Combining our data on natural samples with the previously published data on natural and synthetic compounds,we propose a new scheme of CaAl_(2)Si_(2)O_(8)polymorphs stability.Our results indicate that CaAl_(2)Si_(2)O_(8)polymorphs could be used for temperature estimations for both Earth and planetary sciences.