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Radioluminescent multi-doped yttrium pyrosilicate (YPS) nanoparticles were synthesized using a high temperature multi-composite reactor. The luminescent activators explored were cerium, terbium, and europium.

X-rays offer low tissue attenuation with high penetration depth when used in medical applications and when coupled with radioluminescent nanoparticles, offer novel theranostic opportunities. In this role, the ideal scintillator requires a high degree of crystallinity for an application relevant radioluminescence, yet a key challenge is the irreversible aggregation of the particles at most crystallization temperatures. In this communication, a high temperature multi-composite reactor (HTMcR) process was successfully developed to recrystallize monodisperse scintillating particulates by employing a core-multishell architecture. The core–shell morphology of the particles consisted of a silica core over-coated with a rare earth (Re = Y 3 + , Lu 3 + , Ce3+) oxide shell. This core–shell assembly was then encapsulated within a poly(divinylbenzene) shell which was converted to glassy carbon during the annealing & crystallization of the silica/rare earth oxide core–shell particle. This glassy carbon acted as a delamination layer and prevented the irreversible aggregation of the particles during the high temperature crystallization step. A subsequent low temperature annealing step in an air environment removed the glassy carbon and resulted in radioluminescent nanoparticles. Two monodisperse nanoparticle systems were synthesized using the HTMcR process including cerium doped Y2Si2O7 and Lu2Si2O7 with radioluminescence peaks at 427 and 399 nm, respectively. These particles may be employed as an in vivo light source for a noninvasive X-ray excited optogenetics.

The structures of seven compounds based on guanidinium cations, isolated sulfate anions, and additional organic cations and solvent molecules are reported. All seven compounds, (C(NH2)3)2(SO4) (1), (C(NH2)3)3(C5H6N)(SO4)2 (2), (C(NH2)3)3(C5H6N)(SO4)2·H2O (3), (C(NH2)3)3(C5H6N)(SO4)2·CH3OH (4), (C(NH2)3)11(C5H6N)(SO4)6·2.5C2H5OH (5), (C(NH2)3)3(C6H16N)(SO4)2 (6), and (C(NH2)3)2(C20H26N2O2)(SO4)2 (7) crystallize without a center of symmetry, and are built of related motifs of six-membered rings via hydrogen bonding of three guanidinium cations and three sulfate anions. These six-membered rings form extended sheets and frameworks through additional hydrogen bonding interactions. The presence of additional cations and solvent molecules in varying ratios add structural diversity by modifying the guanidinium sulfate frameworks, but retaining the acentricity of the structures. The study reveals a remarkable tendency for these guanidinium sulfate frameworks to crystallize without a center of symmetry, and furthermore, in polar or chiral space groups. This provides a potential pathway for the use of hydrogen bonding interactions to design structures having interesting physical or nonlinear optical properties.

An examination of manganese silicates and germanates revealed unusual structural motifs and extremely different chemistries, with identical hydrothermal reactions forming K2Mn2Si3O9 versus K11Mn21Ge32O86(OH)9(H2O). The germanate is exceptional in both its c-axis length (exceeding 76 A) and unit cell volume (nearly 18000 A3), the largest known polygermanate structure to our knowledge.

A novel technique for the absolute stereochemical determination of alcohols has been developed that uses crystallization of guanidinium salts of organosulfates. The simple one-pot, two-step process leverages facile formation of guandinium organosulfate single crystals for the straightforward determination of the absolute stereochemistry of enantiopure alcohols by means of X-ray crystallography. The strong hydrogen bonding network drives the stability of the crystal lattice and allows for a diverse range of organic alcohol substrates to be analyzed.

Materials with triangular arrangements of transition metal ions are of great interest for their complex magnetism resulting from geometric frustration. This paper describes the stepwise formation of kagome lattices of open shell transition-metal ions from half-delta chains to delta/sawtooth chains, and finally kagome nets. The systems can be viewed as a testbed for magnetic studies since a variety of spin states can be introduced across the same structure type, and progress through increasing levels of structural complexity and dimensionality. The synthetic and structural development of this continuum is studied here in well-formed single crystals of A2 M3 (MoO4 )3 (OH)2 (A=K, Rb; M=Mn, Co), CsM2 (MoO4 )2 (OH) (M=Mn, Fe, Co, Zn), and KM3 (MoO4 )2 O(OH) (M=Mn).

The reactions of Ln2O3 (Ln = La Lu) with ReO2 were examined in high temperature hydrothermal water (650 °C). In all cases the rhenium oxide was added in a three-fold excess. No external mineralizer was needed and the rhenate itself acted as a sufficient mineralizer to form high quality single crystals of several crystalline products. These form in good yield with compositions varying as a function of the size of the rare earth ion. The largest sesquioxide, La2O3, forms the well-known La4Re6O19 phase, but when Ln = Nd or Pr, a new product, Ln2Re2O7(OH), is isolated. Reactions with Ln = Sm Tb form Ln4Re2O11, and those with Dy Lu form Ln2ReO5. The new Ln2Re2O7(OH) series was characterized as a new structure type by single crystal X-ray diffraction. This structure features a tetrameric Re4O16 cluster embedded in a lanthanide oxide framework. Additional detailed structural data is also provided for Tb4Re2O11 and Eu4Re2O11, which were not previously reported for the Ln4Re2O11 family. In Ln2Re2O7(OH), no direct Re Re bond (Re Re = 2.60 A) is observed while Ln4Re2O11 appears to possess a rhenium-rhenium double bond with a Re Re distance of 2.42 A. Single crystal Raman data supports both of these characterizations. Magnetic data is reported for Ln2Re2O7(OH) and Tb4Re2O11, and their behavior appears to be dominated by the f-element magnetic moments. At low temperatures Tb4Re2O11 displays possible canted antiferromagnetic coupling.

Two new structurally related cesium manganese vanadates have been synthesized by a high-temperature (580 °C) hydrothermal synthetic method utilizing halide brine mineralizers. Both structures Cs6Mn(H2O)2(VO3)8 (I) and Cs5KMn(H2O)2(VO3)8 (II) are isostructural crystallizing in the tetragonal space group P4/mnc. The first structure, Cs6Mn(H2O)2(VO3)8 (I) has unit cell dimensions of a = 13.6830(4) A, c = 8.6476(3) A and the second structure, Cs5KMn(H2O)2(VO3)8 (II), has unit cell dimensions of a = 13.5015(4) A, c = 8.5372(3) A. The structures are built from a manganese vanadate chain, which consists of [Mn(H2O)2O4] units that are coordinated to one another by a unique sinusoidal vanadate chain, (VO3)n. Both structures have well-ordered alkali metal atoms, with the potassium atoms of II exhibiting preferential site occupancy. Both compounds were characterized by single crystal X-ray diffraction and infrared spectroscopy, to identify the characteristic O–H and V–O modes. Crystals of Cs6Mn(H2O)2(VO3)8 and Cs5KMn(H2O)2(VO3)8 were synthesized from hydrothermal brines and their structures determined by single crystal X-ray diffraction, revealing preferential, ordered site substitution of the alkali metals.

Two new structural types of BaREGeO4(OH) and BaRE10(GeO4)4O8 (RE = Ho3+,Er3+) single crystals were synthesized via high-temperature and high-pressure hydrothermal synthesis. The BaREGeO4(OH) compounds were found to crystallize in the orthorhombic space group Pbca. BaHoGeO4(OH) is used as a representative of the family with cell parameters of a = 5.7175(2) A, b = 10.1556(5) A, c = 10.6189(9) A and V = 964.97(8) A3. The BaREGeO4(OH) structure contains a one-dimensional chain of rare-earth polyhedra linked through edge sharing of oxygen atoms. High density BaRE10(GeO4)4O8 crystals crystallize in the monoclinic space group C2/m and feature a sheet like arrangement of rare-earth oxide polyhedra with Keggin-like features. BaHo10(GeO4)4O8 is used as a representative of this structure type with cell parameters of a = 12.4533(8) A, b = 7.2008(5) A, c = 12.0034(8) A, β = 100.183(2)⁰ and V = 1059.43(12) A3. Barium polyhedra and isolated GeO4 units aid in connecting the rare earth oxide framework to extend it in three-dimensional (3-D) space. Characterization by single crystal X-ray diffraction and Raman and photoluminescence spectroscopies is reported.

X-ray excited optical luminescence from nanophosphors can be used to selectively generate light in tissue for imaging and stimulating light-responsive materials and cells. Herein, we synthesized X-ray scintillating NaGdF

The magnetic properties are reported for three members of the glaserite series of compounds, Na2BaM(VO4)2, M = Mn, Mn0.6Co0.4, and Co. Large single crystals are grown using a high-temperature hydrothermal synthesis method. This structure type exhibits a triangular magnetic lattice in which M2+O6 octahedra are interconnected with nonmagnetic (VO4)3- groups. All the structures crystallize at room temperature with rigid trigonal symmetry (space group P3 m1); however, at lower temperatures both Na2BaMn(VO4)2 and Na2BaMn0.6Co0.4(VO4)2 undergo a structural transition to lower symmetry (monoclinic, C2/ c). The bulk magnetic measurements indicate that Mn- and Co-structures are antiferromagnetic and ferromagnetic, respectively. Na2BaMn0.6Co0.4(VO4)2 does not show any long-range ordering down to 0.5 K, although a broad heat capacity anomaly near 1.2 K suggests short-range magnetic order or freezing into a spin-glass-like state related to the chemical disorder and resulting competing magnetic interactions. The magnetic structures of Na2BaMn(VO4)2 and Na2BaCo(VO4)2 were determined using neutron powder diffraction. At zero magnetic field, Na2BaMn(VO4)2 possesses an antiferromagnetic structure with the moments ordered in a Neel-type arrangement and aligned along the C4 axis of the octahedra. Under applied magnetic field at 0.3 K, the evolution of the magnetic structure toward a fully polarized state is observed. Na2BaCo(VO4)2 represents a ferromagnetic (FM) magnetic structure with Co moments aligned parallel to the c-axis direction. The relationships between these structures and magnetic properties are discussed.

Reactions are reported of early rare earth oxides, RE2O3 (RE = La, Pr, Nd) with Ta2O5 under hydrothermal conditions (650 °C, 1.5 kbar) in concentrated aqueous hydroxide (20-30 M KOH) as a mineralizer. Under various stoichiometries several members of two new structure types were isolated, Ln2TaO5(OH) (Ln = La, Pr) and Ln3Ta2O9(OH) (Ln = Pr, Nd). The analogous niobate La2NbO5(OH) was also obtained. Both structure types were characterized by single crystal X-ray diffraction and contain pentavalent tantalatum oxide octahedra and complex rare earth oxide frameworks. The Ln2TaO5(OH) structure type contains Ln-O8 and Ln-O9 building blocks and TaO6 octahedra in a 3-D framework. It contains a 3-D rare earth oxide framework formed by from zig-zag chains of rare earth oxides linking sheets of rare earth oxides. The tantalates form edge-shared Ta2O10 dimers occupying gaps in the rare earth oxide frameworks. The structure of Ln3Ta2O9(OH) contains two types of 2-D rare earth oxide slabs built of seven and eight coordinate rare earth metals. The tantalate units form 2-D slabs through a multiple corner-sharing scheme of TaO6 octahedra. The Ln3Ta2O9(OH) structure type has an interesting close structural relationship to the previously reported rare earth titanate La5Ti4O15(OH), which is discussed. The presence of hydroxide in the lattice is confirmed by IR spectroscopy and the H atom locations are assigned unambiguously using bond valence sums.

Large single crystals of Yb2Ge2O7 in the cubic Fd3m space group, are synthesized and characterized from a high-temperature hydrothermal method (650°C/200 MPa in 1 M KF). The cubic phase displays spin frustration and possibly nonclassical quantum-spin behavior at low temperature. This is the first report of single crystals of this important phase of size and quality suitable for single-crystal neutron diffraction.

The growth of large high quality single crystals of three lithium silicates and germanates Li 2 SiO 3 , Li 2 SiO 5 , and Li 2 GeO 3 is described. The crystals are all grown using hydrothermal fluids at 650 °C and 1 kbar using simple oxide feedstock and 3–6 M LiOH serving as both the lithium ion source and mineralizer. The crystals could be grown by spontaneous transport without any specific seeding, and grew between 2 and 10 mm/edge and without evidence of cracking, physical twinning or multiple domain structures. The crystals were characterized by single crystal diffraction, UV–vis spectroscopy and Raman spectroscopy. All the crystals are acentric and polar. Preliminary nonlinear optical properties were investigated using the Kurtz method and indicate that the crystals exhibit Type-1 phase matching ability, and Li 2 SiO 3 demonstrates a significant nonlinear optical conversion efficiency, making it of potential interest as a UV NLO crystal.

The structure of Cs3 RESi6 O15 , where RE=Dy-Lu, Y, In, is unusual in that it contains octahedrally coordinated rare-earth ions; their relative orientation dictates the structure, as they rotate about the c-axis supported by the cyclic Si6 O15 framework. The repeat unit of the rotation is eight units generating a very long (ca. 57 A) unit cell axis. This unusual repeat unit is created by the structural flexibility of the hexasilicate ring, which is in turn affected by the size of the rare earth ion as well as the size of alkali ion residing within the silicate layers. Previous work showed for the smaller Sc3+ ion, the rotation of the octahedra is not sufficient to achieve closure at an integral repeat unit and an incommensurate structure results. The products are prepared as large, high quality single crystals using a high-temperature (650 °C) hydrothermal method with CsOH and F- mineralizers. The presence of fluoride is essential to the formation of the product.

Reactions of rare-earth oxides with TiO2 were performed in high temperature (650–700 °C) hydrothermal fluids. Two different mineralizer fluids were examined, 20 M KOH and 30 M CsF, and their respective products analyzed. When concentrated KOH fluids were used, single crystals of a variety of new OH− containing species were isolated and structurally characterized: RE5Ti4O15(OH) (RE = La, Er) I, Sm3TiO5(OH)3II and RE5Ti2O11(OH) (RE = Tm–Lu) III. La5Ti4O15(OH) I crystallizes in the orthorhombic space group Pnnm with unit cell dimensions of a = 30.5152(12) A, b = 5.5832(2) A, c = 7.7590(3) A and V = 1321.92(9) A3, Z = 4. Sm3TiO5(OH)3II crystallizes in the monoclinic space group P21/m with unit cell parameters of a = 5.6066(2) A, b = 10.4622(4) A, c = 6.1258(2) A and β = 104.7390(10)°, V = 347.50(2) A3, Z = 2. Lu5Ti2O11(OH) III crystallizes in the monoclinic space group C2/m with unit cell dimensions of a = 12.1252(9) A, b = 5.8243(4) A, c = 7.0407(5) A, β = 106.939(3)° and V = 475.65(6) A3, Z = 2. When concentrated fluoride solutions are used, mostly RE2Ti2O7 type compounds were isolated in either cubic or monoclinic phases. In the case of cerium, Ce2Ti4O11IV was isolated that crystallizes in the monoclinic space group C2/c with unit cell parameters of a = 13.6875(7) A, b = 5.0955(3) A, c = 12.8592(7) A, β = 108.964(2)° and V = 848.18(8) A3, Z = 4. The synthesis, structural characterization, and supporting characterization are reported for all compounds. The work highlights the complementary nature of hydroxide and fluoride fluids in studying the reactivity of refractory oxides.

Two new halide-containing cesium manganese vanadates have been synthesized by a high-temperature (580 °C) hydrothermal synthetic method from aqueous brine solutions. One compound, Cs3Mn(VO3)4Cl, (1) was prepared using a mixed cesium hydroxide/chloride mineralizer, and crystallizes in the polar noncentrosymmetric space group Cmm2, with a = 16.7820(8) A, b = 8.4765(4) A, c = 5.7867(3) A. This structure is built from sinusoidal zig-zag (VO3)n chains that run along the b-axis and are coordinated to Mn2+ containing (MnO4Cl) square-pyramidal units that are linked together to form layers. The cesium cations reside between the layers, but also coordinate to the chloride ion, forming a cesium chloride chain that also propagates along the b-axis. The other compound, Cs2Mn(VO3)3F, (2) crystallizes in space group Pbca with a = 7.4286(2) A, b = 15.0175(5) A, c = 19.6957(7) A, and was prepared using a cesium fluoride mineralizer. The structure is comprised of corner sharing octahedral Mn2+ chains, with trans fluoride ligands acting as bridging units, whose ends are capped by (VO3)n vanadate chains to form slabs. The cesium atoms reside between the manganese vanadate layers, and also play an integral part in the structure, forming a cesium fluoride chain that runs along the b-axis. Both compounds were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and single-crystal Raman spectroscopy. Additionally, the magnetic properties of 2 were investigated. Above 50 K, it displays behavior typical of a low dimensional system with antiferromagnetic interactions, as to be expected for linear chains of manganese(ii) within the crystal structure.

Three new strontium manganese vanadates, Sr 2 Mn 2 (V 3 O 10 )(VO 4 ) ( I ), Sr 3 Mn(V 2 O 7 ) 2 ( II ), and Sr 2 Mn(VO 4 ) 2 (OH) ( III ), were prepared using a high temperature (580 °C) hydrothermal method with various chloride salts as the mineralizer. Minor differences in the chloride stoichiometry led to significant differences in product. Compound I crystallizes in the monoclinic space group P 2 1 / c ( a = 6.8773(12) A, b = 15.061(3) A, c = 11.609(2) A, β = 96.745(8)°), and consists of edge-shared octahedral manganese(II) dimers coordinated by trimeric [V 3 O 10 ] and monomeric [VO 4 ] groups. Compound II crystallizes in the tetragonal crystal system, P 4 3 2 1 2 ( a = 6.9951(2) A, c = 25.4390(7) A), and is built from monomeric manganese(II) octahedra chelated by two pyrovanadate [V 2 O 7 ] groups and linked to each other by additional pyrovanadates to form layers. Compound III is a noncentrosymmetric variation on the brackebuschite structure type, crystallizing in the monoclinic space group P 2 1 ( a = 7.6316(3) A, b = 6.1204(3) A, c = 8.6893(3) A, β = 111.3940(10)°). The structure is composed of octahedral manganese(III) edge-sharing chains coordinated to corner-sharing monomeric [VO 4 ] groups, thereby forming a manganese vanadate chain. All compounds were characterized by single-crystal X-Ray diffraction, powder X-Ray diffraction, infrared spectroscopy and single-crystal Raman spectroscopy. Density functional theory calculations were employed to investigate the relative stability of compound III .

Structural variations across a series of barium rare earth (RE) tetrasilicates are studied. Two different formulas are observed, namely those of a new cyclo-silicate fluoride, BaRE2Si4O12F2 (RE = Er3+–Lu3+) and new compounds in the Ba2RE2Si4O13 (RE = La3+–Ho3+) family, covering the whole range of ionic radii for the rare earth ions. The Ba2RE2Si4O13 series is further subdivided into two polymorphs, also showing a dependence on rare earth ionic radius (space group P{\overline 1} for La3+–Nd3+, and space group C2/c for Sm3+–Ho3+). Two of the structure types identified are based on dinuclear rare earth units that differ in their crystal chemistries, particularly with respect to the role of fluorine as a structural director. The broad study of rare earth ions provides greater insight into understanding structural variations within silicate frameworks and the nature of f-block incorporation in oxyanion frameworks. The single crystals are grown from high-temperature (ca 953 K) hydrothermal fluids, demonstrating the versatility of the technique to access new phases containing recalcitrant rare earth oxides, enabling the study of structural trends.

Two new alkali vanadate carbonates with divalent transition metals have been synthesized as large single crystals via a high-temperature (600 °C) hydrothermal technique. Compound I, Rb2Mn3(VO4)2CO3, crystallizes in the trigonal crystal system in the space group P3[combining macron]1c, and compound II, K2Co3(VO4)2CO3, crystallizes in the hexagonal space group P63/m. Both structures contain honeycomb layers and triangular lattices made from edge-sharing MO6 octahedra and MO5 trigonal bipyramids, respectively. The honeycomb and triangular layers are connected along the c-axis through tetrahedral [VO4] groups. The MO5 units are connected with each other by carbonate groups in the ab-plane by forming a triangular magnetic lattice. The difference in space groups between I and II was also investigated with Density Functional Theory (DFT) calculations. Single crystal magnetic characterization of I indicates three magnetic transitions at 77 K, 2.3 K, and 1.5 K. The corresponding magnetic structures for each magnetic transition of I were determined using single crystal neutron diffraction. At 77 K the compound orders in the MnO6-honeycomb layer in a Néel-type antiferromagnetic orientation while the MnO5 triangular lattice ordered below 2.3 K in a colinear 'up-up-down' fashion, followed by a planar 'Y' type magnetic structure. K2Co3(VO4)2CO3 (II) exhibits a canted antiferromagnetic ordering below TN = 8 K. The Curie-Weiss fit (200-350 K) gives a Curie-Weiss temperature of -42 K suggesting a dominant antiferromagnetic coupling in the Co2+ magnetic sublattices.

A higher-temperature hydrothermal approach (650–700 °C) has been employed in the crystal growth of Lu 2 O 3 and its lanthanide-doped analogs. Carefully controlled thermal gradients of 30° or less were also used to minimize the number of nucleation sites. The resulting crystals exhibit improvements in size and optical clarity over those grown at 600–650 °C. These outcomes are likely also attributed to a greater stability of Lu 2 O 3 relative to LuO(OH) at the higher temperature conditions. The doping of Lu 2 O 3 single crystals has been extended to encompass all spectroscopically active trivalent rare earth ions. Absorption spectra have been obtained of a wide range of lanthanide-doped Lu 2 O 3 single crystals from 80 to 298 K and the spectra of Nd:Lu 2 O 3 are reported as a representative example herein.

Large single crystals of A2Mn2V2O7F2 (A=Rb, Cs) and Mn2VO4F were grown using a high-temperature (~600 °C) hydrothermal technique. Single crystal X-ray diffraction and powder X-ray diffraction were utilized to characterize the structures, which both possess MnO4F2 building blocks. The A2Mn2V2O7F2 series crystallizes as a new structure type in space group Pbcn (No. 60), Z=4 (Rb2Mn2V2O7F2: a=7.4389(17) A, b=11.574(3) A, c=10.914(2) A; Cs2Mn2V2O7F2: a=7.5615(15) A, b=11.745(2) A, c=11.127(2) A). The structure is composed of zigzag chains of edge-sharing MnO4F2 units running along the a-axis, and interconnected through V2O7 pyrovanadate groups. Temperature dependent magnetic susceptibility measurements on this interesting one-dimensional structural feature based on Mn2+ indicated that Cs2Mn2V2O7F2 is antiferromagnetic with a Neel temperature, TN=~3 K and a Weiss constant, θ, of −11.7(1) K. Raman and infrared spectra were also analyzed to identify the fundamental V–O vibrational modes in Cs2Mn2V2O7F2. Mn2(VO4)F crystalizes in the monoclinic space group of C2/c (no. 15), Z=8 with unit cell parameters of a=13.559(2) A, b=6.8036(7) A, c=10.1408(13) A and β=116.16(3)°. The structure is associated with those of triplite and wagnerite. Dynamic fluorine disorder gives rise to complex alternating chains of five-and six-coordinate Mn2+. These interpenetrating chains are additionally connected through isolated VO4 tetrahedra to form the condensed structure.

New complex manganese vanadate materials were synthesized as high-quality single crystals in multi-millimeter lengths using a high-temperature, high-pressure hydrothermal method. One compound, Mn5(VO4)2(OH)4, was grown from Mn2O3 and V2O5 in 3 M CsOH at 580 °C and 1.5 kbar. Changing the mineralizer to 1 M CsOH/3MCsCl leads to the formation of another product, Mn6O(VO4)2(OH). Both compounds were structurally characterized by single-crystal X-ray diffraction (Mn5(VO4)2(OH)4: C2/m, Z = 2, a = 9.6568(9) Å, b = 9.5627(9) Å, c = 5.4139(6) Å, β = 98.529(8)°; Mn6O(VO4)2(OH): P21/m, Z = 2, a = 8.9363(12) Å, b = 6.4678(8) Å, c = 10.4478(13) Å, β = 99.798(3)°), revealing interesting low-dimensional transition-metal features. Mn5(VO4)2(OH)4 possesses complex honeycomb-type Mn-O layers, built from edge-sharing [MnO6] octahedra in the bc plane, with bridging vanadate groups connecting these layers along the a-axis. Mn6O(VO4)2(OH) presents a more complicated structure with both octahedral [MnO6] and trigonal bipyramidal [MnO5] units. A different pattern of planar honeycomb sheets are formed by edge-shared [MnO6] octahedra, and these sublattices are connected through edge-shared dimers of [MnO5] trigonal bipyramids to form corrugated sheets. Vanadate groups again condense the sheets into a three-dimensional framework. Infrared and Raman spectroscopies indicated the presence of OH groups and displayed characteristic Raman scattering due to vanadate groups. Temperature-dependent magnetic studies indicated Curie-Weiss behavior above 100 K with significant anti-ferromagnetic coupling for both compounds, with further complex magnetic behavior at lower temperatures. The data indicate canted anti-ferromagnetic order below 57 K in Mn5(VO4)2(OH)4 and below 45 K in Mn6O(VO4)2(OH). Members of another class of compounds, K2M3(VO4)2(OH)2 (M = Mn, Co), also containing a honeycomb-type sublattice, were also synthesized to allow a comparison of the structural features across all three structure types and to demonstrate extension to other transition metals.

The hydrothermal growth, doping, and low temperature spectral characterization of Yb doped Lu 2 O 3 was investigated. The absorption of the lutetia-based sesquioxide laser material Yb:Lu 2 O 3 at temperatures of 80, 150, 200, 250, and 298 K, in the wavelength range of 850–1100 nm are reported. Data for both single crystal and ceramic Yb:Lu 2 O 3 were obtained. The resulting absorption cross-section data will enable the further evaluation of Yb:Lu 2 O 3 as a very promising high power cryogenic laser material.

A series of transition metal vanadate crystals were prepared using a high temperature (580 °C) hydrothermal method. The compounds all had the general formula A 2 AEM (VO 4 ) 2 ( A =K, Na, Li; AE =Ba, Sr; M =Co, Fe, Mn). They are all variations of the glaserite structural type and range in symmetry from P- 3 m 1 to P -3 to P 2 1 / c . Most of the derivatives contain a planar three-fold rotation operation, making them possible spin frustration candidates. Single crystal structural analyses were performed on many of the derivatives to obtain a detailed understanding of the distortions of the tetrahedral building blocks that accommodate the symmetry distortions. A hydrothermal growth method was developed to grow high quality single crystals of sizes up to 2–3 mm/edge. This method can be generalized for large crystal growth to enable magnetic and neutron diffraction studies that require relatively large single crystals.

The solid-state chemistry of novel metal silicate and borosilicate crystals containing Eu2+ and Eu3+ in high temperature hydrothermal fluids was investigated. It was found that europium ions could be readily incorporated into a number of crystals using a variety of simple glass-based feedstocks. The hydrothermal growth reactions were performed at nearly 600 °C in 1–5 M NaOH mineralizer fluids, and this was found to be a versatile route to both europium ion oxidation states with Eu acting as either a fundamental structural building block or a dopant ion. Several new single crystals were identified including two new apatites as well as a new europium borosilicate. The apatites crystallize in space group P63/m with a = 9.4619(13) A and c = 7.0054(14) A for Eu10(SiO4)6O2, and a = 9.4413(13) A and c = 6.9087(14) A for NaEu9(SiO4)6O2. The new borosilicate, Eu2SiB2O8, crystallizes in space group Pbcn with a = 13.310(3) A, b = 4.4247(9) A and c = 9.2394(18) A. The investigation of Eu-doped borosilicates demonstrated the strong blue emission generated from 370 nm excitation that was expected for the Eu2+ doped materials, as well as the less intense orange-red emission expected for the Eu3+ dopants. The hydrothermal reactions naturally facilitated a degree of europium reduction in Eu:Ba3Si2B6O16. It was found that the oxidation states of europium in the final product could be further controlled by using hydrazine as a reducing reagent.

The structural variations of several alkali metal rare earth fluoride single crystals are summarized. Two different stoichiometric formulations are considered, namely those of ARE2F7 and ARE3F10 (A = K, Rb, Cs; RE = Y, La–Lu), over a wide range of ionic radii of both the alkali and rare earth (RE) ions. Previously reported and several new single-crystal structures are considered. The new single crystals are grown using hydrothermal methods and the structures are compared with literature reports of structures grown from both melts and hydrothermal fluids. The data reported here are combined with the literature data to gain a greater understanding of structural subtleties surrounding these systems. The work underscores the importance of the size of the cations to the observed structure type and also introduces synthetic technique as a contributor to the same. New insights based on single-crystal structure analysis in the work introduce a new disordered structure type in the case of ARE2F7, and examine the trends and boundaries of the ARE3F10 stoichiometry. Such fundamental structural information is useful in understanding the potential applications of these compounds as optical materials.

The synthesis and upconversion properties of trigonal glaserite-type K 3 Y(VO 4 ) 2 co-doped with Er 3+ /Yb 3+ , Ho 3+ /Yb 3+ , or Tm 3+ /Yb 3+ were studied. Powder samples were synthesized by solid state reactions at 1000 °C for 48 h, while well-formed hexagonal single crystals of the same were grown hydrothermally using 10 M K 2 CO 3 at 560–650 °C. Infrared-to-visible upconversion by Er 3+ /Yb 3+ , Ho 3+ /Yb 3+ , or Tm 3+ /Yb 3+ codoped-K 3 Y(VO 4 ) 2 glaserite powder and single crystals was observed, and the upconversion spectral properties were studied as a function of different Er 3+ , Tm 3+ , Ho 3+ , and Yb 3+ ion concentrations. The process is observed under 980 nm laser diode excitation and leads to strong green (552 nm) and red (659 nm) emission for Er 3+ /Yb 3+ , green (549 nm) and red (664 nm) emission for Ho 3+ /Yb 3+ , and blue (475 nm) and red (647 nm) emission for Tm 3+ /Yb 3+ . The main mechanism that allows for up-conversion is attributed the energy transfer among Yb 3+ and the various Er 3+ /Ho 3+ /Tm 3+ ions in excited states. These results illustrate the large potential of co-doped alkali double vanadates for photonic applications involving optoelectronics devices.

Single crystals of LiKTmF 5 were grown hydrothermally. Its crystal structure was studied with single-crystal X-ray diffraction to 8.6 GPa. The material is monoclinic (P2 1 /c, Z = 4) and does not undergo any phase transition in the pressure range studied here. The analysis of its pseudosymmetry with respect to the minimal k -supergroup C2/m reveals that the deviations of the individual atoms from the respective higher symmetrical positions in C2/m are increasing on compression, i.e., due to the reduction of the unit-cell volume. Such a behaviour is the opposite of the effect of incorporation of various M cations in the LiKMF 5 materials (M:Y and rare earths) at atmospheric conditions, since LiKYbF 5 and LiKLuF 5 with the smallest unit cells crystallize in space group C2/m, while LiLYF 5 with a larger unit cell has P2 1 /c symmetry.

The structural and magnetic properties of a glaserite-type Na

Two terbium germanates have been synthesized via high-temperature and high-pressure hydrothermal synthesis with 20 M KOH as a mineralizer using Tb

We have investigated the hydrothermal growth of, and spectrally characterized, the lutetium based laser materials Nd:LuAG, Yb:LuAG, and Yb:Lu2O3. Absorption cross-section data are presented for Nd:LuAG at 83, 175, and 295 K. Absorption cross-section data was also obtained for Yb:LuAG at 83, 175, and 295 K; the 295 K data was used to generate emission cross-sections using the method of reciprocity. For Yb:Lu2O3, we present absorption cross-sections at 295 K as well as emission cross-sections derived using reciprocity.

Potassium yttrium double vanadates (K3Y(VO4)2) doped with Bi3+ or Dy3+ and codoped with Bi3+ and Dy3+ have been synthesized by solid state reactions at 1000 °C for 48 h and their photoluminescence properties investigated. Efficient energy transfer from the vanadate (VO43−) group or bismuth ions to the rare earth ion has been established by photoluminescence investigation upon UV excitation and results in blue and yellow emissions at 480–489 nm and 572–580 nm respectively. The codoping of Bi3+ and Dy3+ into K3Y(VO4)2 results in enhanced yellow emission band while the blue emission band remains relatively unchanged. The intensities of emission for the studied materials were investigated as a function of different Bi3+ and Dy3+ ion concentrations. The presented results show K3Y(VO4)2 phosphors as potential candidates W-LEDs applications.

Several new borate compounds, Ba11B26O44(PO4)2(OH)6 (1), Li9BaB15O27(CO3) (2), and Ba3Si2B6O16 (3) were synthesized containing other hetero-oxyanion building blocks in addition to the borate frameworks. They were all prepared under hydrothermal conditions and characterized by single crystal and powder X-ray diffraction, and IR spectroscopy. Crystal data: For 1; space group P21/c, a=6.8909 (14) A, b=13.629 (3) A, c=25.851 (5) A, β=90.04 (3)°; For 2; space group P-31c, a=8.8599 (13) A, c=15.148 (3) A; For 3; space group P-1, a=5.0414 (10) A, b=7.5602 (15) A, c=8.5374 (17) A, α=77.15 (3)°, β=77.84 (3)°, γ=87.41 (3)° for 3. Compounds 1 and 2 contain isolated oxyanions [PO4]3− and [CO3]2− respectively, sitting in channels created by the borate framework, while structure 3 has the [SiO4]4− groups directly bonded to the borate groups creating a B–O–Si framework.

K2ThF6 and K7Th6F31 were prepared hydrothermally as single crystals. Their structures were investigated with single-crystal X-ray diffraction at ambient conditions and at high pressures using diamond anvil cells. The results of this study indicate that the two materials, with chains of face-sharing tricapped trigonal prisms ThF9 and with layers of square antiprisms ThF8 sharing their edges in Th2F14 doublets, respectively, are structurally stable at least to about 9 GPa at room temperature. This observation suggests that, in general, moderate high pressure has no effect on the coordination polyhedra around the Th atoms and the topology of the structure of complex thorium fluorides. The bulk compressibility of the thorium fluorides entirely depends on the alkali metal present in the structure.

The growth of Lu3Al5O12 (LuAG) as high quality single crystals using the hydrothermal method is described. The growth protocol is similar to that of Y3Al5O12 (YAG) using binary oxides (Lu2O3 and sa...

The hydrothermal synthesis and crystal growth of LiLuF 4 were investigated. Small crystals of LiLuF 4 were produced but while investigating various alkali fluoride mineralizers, a new series of alkali lithium lutetium fluorides, including, LiKLuF 5 and LiNaLu 2 F 8 , were synthesized under hydrothermal conditions (570 °C at 12.5 kpsi). The mineralizer KF leads to formation of a new compound LiKLuF 5 crystallized in the space group C 2/ m with the lattice parameters a = 6.2328(12), b = 11.709(2), c = 6.3986(13), β = 113.87(3). Tm and Yb analogs were also synthesized using the same conditions. Use of NaF as mineralizer leads to a new compound LiNaLu 2 F 8 , crystallized in space group Cmcm , a = 10.3181(21), b = 8.2393(16), c = 6.9565(14). Several doped compounds were also isolated and electronic spectra were obtained.