High-temperature Solution Method Research Articles

The upconversion photoluminescence and temperature sensing abilities of Pb(Zn1/3Nb2/3)O3-9PbTiO3 crystals induced by Er3+/Yb3+ doping

Er3+/Yb3+-doped Pb(Zn1/3Nb2/3)O3-9PbTiO3 ferroelectric crystals were grown by the high-temperature solution method. The micromorphology, phase structure, and upconversion photoluminescence of obtained crystals were analyzed and investigated. As the results suggest, the crystals displayed typical lamellar growth and possessed a pure perovskite structure. Excited by a 980 nm laser, the characteristic upconversion (UC) emissions of Er3+ were observed at room temperature. The luminescence intensity improved with the increasing of excitation power and reached its maximum at 1056 mW. Two-photon process was demonstrated at lower power range. As the temperature increased from 213 to 493 K, the luminescence intensity weakened continuously. An apparent difference in variation trend between two thermally coupled levels (2H11/2 and 4S3/2) was also observed, which was ascribed to the redistribution of electrons at two levels at the heating process. Based on this dependence, the temperature sensing abilities were examined with the help of the fluorescence intensity ratio (FIR) technique. The absolute sensitivity SA increased in the measurement temperature range and its maximum of 0.0033 K-1 was obtained at 493 K. Moreover, low conversion from incident light into heat was also demonstrated, which indicates the feasibility for crystal luminescence at high power pumping. These results make Er3+/Yb3+-doped Pb(Zn1/3Nb2/3)O3-9PbTiO3 crystals become a promising candidate in optical devices and temperature sensors.

Preparation and visible-light-driven photocatalytic property of AgX (X = Cl, Br, I) nanomaterials

Numerous efforts have been attempted to improve the photocatalytic performance of AgX (X = Cl, Br, I), because its drawback of the reduction of Ag+ into Ag0 under illumination would always largely decrease its stability and lifetime. However, the photocatalytic performance of AgX (X = Cl, Br, I) itself has been long ignored. Herein, novel convex polyhedral-like AgCl and AgBr as well as flake-like AgI were successfully prepared by a simple high-temperature solution method at the atmospheric pressure. The as-prepared samples have been verified to possess extremely excellent photocatalytic performance for the degradation of various organic pollutants, including rhodamine B (RhB), methyl orange (MO) as well as doxycycline (DOX) and the deactivation of Staphylococcus aureus (S. aureus). Besides, the stability of AgX (X = Cl, Br, I) has also been investigated in details.

Superconductivity in LaPd2Bi2 with CaBe2Ge2-type structure

Here we report the synthesis and superconductivity of a novel ternary compound LaPd2Bi2. Shiny plate-like single crystals of LaPd2Bi2 were first synthesized by high-temperature solution method with PdBi flux. X-ray diffraction analysis indicates that LaPd2Bi2 belongs to the primitive tetragonal CaBe2Ge2-type structure with the space group P4/nmm (No. 129), and the refined lattice parameters are a = 4.717(2) {\AA}, c = 9.957(3) {\AA}. Electrical resistivity and magnetic susceptibility measurements reveal that LaPd2Bi2 undergoes a superconducting transition at 2.83 K and exhibits the characteristics of type-II superconductivity. The discovery of superconductivity in LaPd2Bi2 with CaBe2Ge2-type structure may help to further understand the possible relationship between the occurrence of superconductivity and the crystal structures in 122-type materials.

Li2 BaSc(BO3 )2 F and LiBa2 Pb(BO3 )2 F with Layered Structures featuring Special Li-O/F Configurations.

Two new borate fluorides, Li2 BaSc(BO3 )2 F and LiBa2 Pb(BO3 )2 F, with layered structures featuring special Li-O/F configurations have been successfully prepared by the high-temperature solution method. Li2 BaSc(BO3 )2 F contains the first reported 2 ∞ [Li2 (BO3 )2 F] double layers that are evolved from 2 ∞ [Be2 BO3 F2 ] single layers in KBe2 BO3 F2 through substituting BeO4 with the LiO3 F tetrahedra. The adjacent double layers are tightly connected by strong Sc-O bonds, generating the strongest interlayer bond and smallest interlayer distance among KBe2 BO3 F2 derivatives with double-layered structures. LiBa2 Pb(BO3 )2 F features 2 ∞ [Li(BO3 )2 F] single layers built up of special LiO4 F2 octahedra and the BO3 triangles. To our best knowledge, the LiO4 F2 octahedron is observed for the first time in borates. Besides, the LiO4 F2 octahedra construct unique 1 ∞ [LiO4 F] straight chains through sharing apical F atoms, which is different from the configurations of the similar six-coordinated LiO6 octahedra in other borates.

Effects of silver nanocomposite (AgI) on Allium cepa: Part I DNA damage assessment with COMET assay

Er3+/Yb3+-doped Pb(Zn1/3Nb2/3)O3-9PbTiO3 ferroelectric crystals were grown by the high-temperature solution method. The micromorphology, phase structure, and upconversion photoluminescence of obtained crystals were analyzed and investigated. As the results suggest, the crystals displayed typical lamellar growth and possessed a pure perovskite structure. Excited by a 980 nm laser, the characteristic upconversion (UC) emissions of Er3+ were observed at room temperature. The luminescence intensity improved with the increasing of excitation power and reached its maximum at 1056 mW. Two-photon process was demonstrated at lower power range. As the temperature increased from 213 to 493 K, the luminescence intensity weakened continuously. An apparent difference in variation trend between two thermally coupled levels (2H11/2 and 4S3/2) was also observed, which was ascribed to the redistribution of electrons at two levels at the heating process. Based on this dependence, the temperature sensing abilities were examined with the help of the fluorescence intensity ratio (FIR) technique. The absolute sensitivity SA increased in the measurement temperature range and its maximum of 0.0033 K-1 was obtained at 493 K. Moreover, low conversion from incident light into heat was also demonstrated, which indicates the feasibility for crystal luminescence at high power pumping. These results make Er3+/Yb3+-doped Pb(Zn1/3Nb2/3)O3-9PbTiO3 crystals become a promising candidate in optical devices and temperature sensors.

The First Examples of Lithium-Containing Mixed-Alkali Strontium Borates with Different Dimensional Anionic Architectures and Short Cutoff Edges.

Three new mixed-alkali strontium borates, Li2 KSr6 (BO3 )5 , Li2 Rb7 Sr24 (BO3 )19 , and Li2 Rb2 SrB18 O30 , have been synthesized by the high-temperature solution method by adjusting the molar ratios of the reactants. They represent the first examples of lithium-containing mixed-alkali strontium borates. The structures of the three compounds show different dimensional anionic architectures, with Li2 KSr6 (BO3 )5 and Li2 Rb7 Sr24 (BO3 )19 possessing isolated BO3 units, whereas Li2 Rb2 SrB18 O30 has three-dimensional (3D) open frameworks with three types of channels occupied by the strontium and rubidium atoms. Interestingly, Li2 KSr6 (BO3 )5 is the first example of a chain composed of LiO5 linked through the sharing of vertexes and edges. However, in Li2 Rb7 Sr24 (BO3 )19 , isolated LiO3 units can be observed, which is also rare in borates. Detailed analysis and comparisons of the structures of the anhydrous mixed-alkali- and alkaline-earth-metal borates and nine-polymeric fundamental building blocks have been made. Furthermore, Li2 Rb7 Sr24 (BO3 )19 and Li2 Rb2 SrB18 O30 present short cutoff edges (<190 nm), which was confirmed by the UV/Vis/NIR diffuse reflectance spectra. These attributes make them attractive for deep-UV optical materials.

Nitrogen-Doped Carbon Coated WS2 Nanosheets as Anode for High-Performance Sodium-Ion Batteries.

Due to the cost-effectiveness of sodium source, sodium-ion batteries (SIBs) have attracted considerable attention. However, SIBs still have some challenges in competing with lithium-ion batteries for practical applications. Particularly, the high rate capability and cycling stability are posing big problems for SIBs. Here, nitrogen-doped carbon-coated WS2 nanosheets (WS2/NC) were successfully synthesized by a high-temperature solution method, followed by carbonization of polypyrrole. When used as anode electrodes for SIBs, WS2/NC composite exhibited high-rate capacity at 386 and 238.1 mAh g−1 at 50 and 2,000 mA g−1, respectively. Furthermore, even after 400 cycle, the composite electrode could still deliver a capacity of ~180.1 mAh g−1 at 1,000 mA g−1, corresponding to a capacity loss of 0.09% per cycle. The excellent electrochemical performance could be attributed to the synergistic effect of the highly conductive nature of the nitrogen-doped carbon-coating and WS2 nanosheets. Results showed that the WS2/NC nanosheets are promising electrode materials for SIBs application.

True-remanent, resistive-leakage and mechanical studies of flux grown 0.64PMN-0.36PT single crystals

Ferroelectric single crystals of 0.64Pb(Mg1/3Nb2/3)O3-0.36PbTiO3 (PMN-PT), which have attracted lot of attention because of its excellent ferroelectric and piezoelectric response, has been successfully grown in the vicinity of morphotropic phase boundary, using high temperature solution method with PbO/B2O3 as flux. The crystals were characterized for its dielectric, ferroelectric, piezoelectric and pyroelectric properties along with the investigation of its domain structure. A high Curie temperature (Tc = 190 °C) was observed in the dielectric study. Well-saturated ferroelectric hysteresis loops with high remanent polarization, good switching and fatigue resistant nature indicated the high ferroelectric quality of the crystals. A high value of piezoelectric coefficient (d33∗ = 1398 pm/V) was obtained from the butterfly loops. True-remanent hysteresis study unveiled the practically usable polarization value, which actually serves as memory component in devices and has never been reported for PMN-PT crystals. Time-dependent compensated hysteresis analysis was carried out to study the resistive-leakage nature of the grown crystals which is also a new study for this system. Weibull statistics was used to analyze the distribution of hardness number and to find the values of critical load for the flux grown PMN-PT crystals which helps to critically analyze materials suitability for device fabrication.

Non-centrosymmetric BaNaP3O9 with a short deep-ultraviolet cutoff edge

A new nonlinear optical (NLO) material, namely, BaNaP3O9 was synthesized by high temperature solution method using PbO as the flux. Crystal of BaNaP3O9 with the non-centrosymmetric P212121 space group displays a novel topological three dimensional (3D) structure with tremendous [Ba4Na4O40] 16-membered ring (16-MR) composed by the BaO8, NaO6 polyhedra, which alternately connected each other by sharing two oxygen atoms. The phosphate compound has a short deep-ultraviolet (deep-UV) cut-off edge about 177 nm and shows a second harmonic generation (SHG) response (0.3 × KDP). Some related optical properties and electronic structures derived from first-principles calculations, were explored.

Li3.366Mg0.317B2O5: The first pyroborate in the Li2O-MgO-B2O3 system

The first pyroborate in the Li2O-MgO-B2O3 system, Li3.366Mg0.317B2O5, has been synthesized via high temperature solution method. The crystal structure can be described as isolated B2O5 units connecting with the Li(2)O5 chains to generate the 2∞[Li2(2)B2O5] layers, which condense alone a-axis, and the co-occupied Li(1)/Mg atoms fill into the voids between the layers. Interestingly, edge- and face-sharing Li(2)O5 polyhedra are rarely found in Li3.366Mg0.317B2O5 and its maternal compound β-Li4B2O5. Moreover, torsion and dihedral angles between two BO3 triangles of B2O5 in Li4−2xMgxB2O5 (x = 0, 0.317, 2) are investigated to explore the structure regulation via introduction of the Mg2+ cation. The structure refinement, thermal stability and infrared spectrum are presented in detail.

Growth, phase and electronic structure of RbTiOPO4 crystals doped with antimony

RbTiOPO4 crystals doped with different concentrations of antimony (Sb) (5–15%) were grown by high-temperature solution method. At the bottom of the crucible, a large amount of crystalline particles and a small amount of flaky crystals were obtained. The crystalline phase, chemical composition and electronic structure of the crystals were analyzed by X-ray diffraction (XRD), electron probe microanalyzer (EPMA) and X-ray photoelectron spectroscopy (XPS). The results show that the doped crystals belong to KTP phase when the concentration of Sb is lower. When the doping concentration of Sb is up to 15%, a new phase is generated and a large amount of white flake materials are produced. From the detailed XPS spectra of P 2p, O 1s and Ti 2p3/2, we found that the binding energy difference between the O 1s and P 2p is stable for different doping concentrations: ΔBE (OP) = 398.1 eV. The binding energy difference between the O 1s and Ti 2p3/2 increases firstly and then decreases with increasing Sb content. Compared with pure RTP, the electronic structure of antimony-doped RTP crystals has changed. The ionicity of TiO bond in the crystal increases with the increase of doping concentration when Sb content is no more than 10%. Sb doping has no significant effect on the PO bond property.

Pb8M(BO3)6 (M = Mg, Ca): Two new borates with large birefringence activated by the ∞[Pb8B6O18]2- double layers

Two new isostructural lead borates, Pb8Mg(BO3)6 and Pb8Ca(BO3)6, have been synthesized via high temperature solution method. The single crystal structures of title compounds contain ∞[Pb8B6O18]2- double layers composed of planar BO3 triangles, Pb(2)O9 and distorted Pb(1)O5 polyhedra, these layers condense in c-axis, and the MgO6 (or CaO6) polyhedra fill into the layers, forming a three-dimensional framework. The stereochemical activity of lone pair (SCALP) electrons were found in the Pb(1)O5 polyhedra, which combine with the BO3 units, generating strong optical anisotropy. The calculated birefringences of Pb8Mg(BO3)6 and Pb8Ca(BO3)6 using first-principles method are 0.15@1064 nm and 0.12@1064 nm, respectively, which are comparable to the commercial α-BaB2O4 (α-BBO) crystal and imply that they probably can be used as birefringent materials. The electronic structures, density of states of title compounds were calculated by density functional theory (DFT). Meanwhile, the TG-DSC curves, infrared spectral and UV–Vis–NIR diffuse reflectance spectral were measured.

Rational Synthesis and Assembly of Ni3S4 Nanorods for Enhanced Electrochemical Sodium-Ion Storage.

Even though advocated as the potential low-cost alternatives to current lithium-ion technology, the practical viability of sodium-ion batteries remains illusive and depends on the development of high-performance electrode materials. Very few candidates available at present can simultaneously meet the requirements on capacity, rate capability, and cycle life. Herein, we report a high-temperature solution method to prepare Ni3S4 nanorods with uniform sizes. These colloidal nanorods readily self-assemble side by side and form microsized superstructures, which unfortunately negates the nanoscale feature of individual nanorods. To this end, we further introduce two-dimensional graphene nanosheets as the spacer to interrupt nanorod self-assembly. Resultant composite presents a marked advantage toward electrochemical storage of Na+ ions. We demonstrate that in half-cells it exhibits large reversible specific capacity in excess of 600 mAh/g, high rate capability with >300 mAh/g retained at 4 A/g, and great cycle life at different current rates. This anode material can also be combined with the NASICON-type Na3V2(PO4)3 cathode in full cells to enable large capacity and good cyclability.

Single crystal growth and characterization of the 112-type iron-pnictide EuFeAs2

The 112-type (Ca, RE)FeAs2 (RE=rare earth) superconductors are very special among the iron-based superconductors for their particular crystal structures with arsenic chain configuration and attractive electronic phase diagram with the coexistence of superconductivity and antiferromagnetism upon carrier doping, while the chemical phases are absent for the low doping level or undoped parent compound. Here we report the single crystal growth method and physical characterizations for the newly discovered Eu 112 type parent compound EuFeAs2. The single crystal of EuFeAs2 is grown by high temperature solution method through using CsCl as the flux under the constant temperature of 800℃ with the molar ratio of the starting materials Eu:Fe:As:CsCl=1:1:4:18. The as-grown crystal is shinyplatelike piece with a typical size of 1 mm1 mm0.2 mm, and quite stable in air. The chemical composition of EuFeAs2 crystal is confirmed by energy-dispersive X-ray spectroscopy. The single crystal X-ray diffraction analysis at room temperature indicates that EuFeAs2 crystallizes into an orthorhombic crystal structure with the space group Imm2 (No. 44), and the refined lattice parameters are a=21.285(9) , b=3.9082(10) , c=3.9752(9) , which are different from those of the Ca 112 compound, but similar to those of unique zigzag As-As chain configuration presented in the layered crystal structure. Electrical resistivity measurements show three anomalies near 110 K, 98 K, and 46 K. The former two anomalies with relatively high temperature imply that the structural and antiferromagnetic transitions are related to Fe2+ sublattice, which is similar to other iron-based parent compounds. The low temperature anomaly at 46 K is attributed to the antiferromagnetic transition of Eu2+ sublattice, which is also confirmed by the corresponding transition observed in the direct current magnetic susceptibility measurement. The magnetic susceptibility of EuFeAs2 exhibits obvious anisotropy blow 46 K when the magnetic field is parallel or perpendicular to the bc plane, while the exact orientation of the Eu2+ moment needs further studying. The discovery of EuFeAs2 provides a new platform for further studying the unique crystal structure and electronic state phase diagrams in the 112-type iron-based superconducting family, and may shed new light on the correlations between superconductivity and magnetism.

LiCs2La(BO3)2 and Li3K9La3(BO3)7: new mixed alkali metal lanthanum borates with three-dimensional open frameworks and short cut-off edges.

Two new mixed alkali metal lanthanum borates, LiCs2La(BO3)2 and Li3K9La3(BO3)7, were synthesized through a high-temperature solution method and millimeter-sized colorless crystals were obtained. The structures of LiCs2La(BO3)2 and Li3K9La3(BO3)7 have an intricate three-dimensional (3D) open framework with one-dimensional (1D) infinite channels surrounded by cation polyhedra and isolated BO3 units. In particular, LiCs2La(BO3)2 exhibits a short cut-off edge <190 nm and a large experimental band gap of 6.20 eV, evidenced by diffuse reflection spectroscopy. Moreover, to better understand the relationship between the electronic structures and optical properties of LiCs2La(BO3)2, theoretical calculations using density functional theory were performed. The result indicated that LiCs2La(BO3)2 has a calculated birefringence of 0.036@1064 nm and the direct band gap is 4.54 eV. In addition, the effects of ion substitution on structural transition and the metal ion/boron ratio on dimensions of the B-O frameworks are also discussed in detail.

MBaYB6O12 (M = Rb, Cs): two new rare-earth borates with large birefringence and short ultraviolet cutoff edges.

Two new rare-earth borates, MBaYB6O12 (M = Rb, Cs), which are the first reported compounds in M2O-BaO-RE2O3-B2O3 (M = Rb, Cs; RE = rare-earth) quaternary systems, have been discovered through a high-temperature solution method and their structures were determined by single-crystal X-ray diffraction. These two compounds are isostructural with the centrosymmetric space group R3[combining macron] (no. 148) and the fundamental building blocks are the B3O6 groups which are nearly parallel to each other. The spectral measurement shows that the cutoff edges of the two compounds are all down to the deep-ultraviolet (deep-UV) region (below 200 nm). And the experimental birefringence of RbBaYB6O12 and RbBaYB6O12 is about 0.12 at 589 nm. Moreover, first-principles theoretical studies were carried out to gain a better understanding of the structure-property relationships. The calculation results demonstrate that both the compounds have a large birefringence of 0.100 at 589 nm, which corresponds to the experimental value. Both experimental and theoretical studies suggest that MBaYB6O12 (M = Rb, Cs) are potential birefringent materials for UV and deep-UV applications.

Growth and spectroscopic properties of Er:Yb:LuPO4 and Er:Yb:Ce:LuPO4 crystals

In this work, we report the growth and spectroscopic properties of high-quality Er:Yb:LuPO4 and Er:Yb:Ce:LuPO4 crystals which are grown by the high-temperature solution method for the first time to the best of our knowledge. The maximum polarization absorption cross sections and the full-width of half-maximum of the Er:Yb:LuPO4 are (3.32 × 10−20 cm2, 17 nm) and (2.41 × 10−20 cm2, 19 nm) for σ- and π-polarization, respectively. The up-conversion luminescence spectra and near-infrared luminescence spectra of both Er:Yb:LuPO4 and Er:Yb:Ce:LuPO4 crystals were recorded under 980 nm pumping. The results exhibit that the up-conversion energy losses are remarkably reduced in Er:Yb:Ce:LuPO4 crystal. Consequently, the luminescence intensity in the waveband of 1.5–1.6 μm of Er:Yb:Ce:LuPO4 is increased by two times compared to Er:Yb:LuPO4.

Structural Insights into Borates with an Anion-Templated Open-Framework Configuration: Asymmetric K2 BaB16 O26 versus Centrosymmetric K3 CsB20 O32 and Na2 M2 NB18 O30 (M=Rb, Cs; N=Ba, Pb).

Five new mixed-metal borate crystals, namely, K2 BaB16 O26 , K3 CsB20 O32 , Na2 Cs2 BaB18 O30 , Na2 Rb2 PbB18 O30 , and Na2 Cs2 PbB18 O30 , have been synthesized by the high-temperature solution method. These structures were characterized by single-crystal X-ray diffraction and their B-O configurations are shown to feature complicated three-dimensional (3D) open-framework structures incorporating different types of channels. For all five compounds, the frameworks can be reduced to four-connected (4-c) uninodal nets with sra-, dia- and nbo-type topologies by assigning the [B5 O10 ]5- and [B3 O7 ]5- clusters as basic nodes. First-principles calculations have shown that the multiple cations in mixed-metal borates influence the ground-state electronic structures and associated optical absorptions. In addition, the crystal structures, thermal stabilities, and IR spectra of the title compounds have also been performed.

Improved Sodium-Ion Storage Performance of Ultrasmall Iron Selenide Nanoparticles.

Sodium-ion batteries are potential low-cost alternatives to current lithium-ion technology, yet their performances still fall short of expectation due to the lack of suitable electrode materials with large capacity, long-term cycling stability, and high-rate performance. In this work, we demonstrated that ultrasmall (∼5 nm) iron selenide (FeSe2) nanoparticles exhibited a remarkable activity for sodium-ion storage. They were prepared from a high-temperature solution method with a narrow size distribution and high yield and could be readily redispersed in nonpolar organic solvents. In ether-based electrolyte, FeSe2 nanoparticles exhibited a large specific capacity of ∼500 mAh/g (close to the theoretical limit), high rate capability with ∼250 mAh/g retained at 10 A/g, and excellent cycling stability at both low and high current rates by virtue of their advantageous nanosizing effect. Full sodium-ion batteries were also constructed from coupling FeSe2 with NASICON-type Na3V2(PO4)3 cathode and demonstrated impressive capacity and cycle ability.

Growth and characterization of LuVO4 single crystals

Large LuVO4 single crystals have been successfully obtained by high-temperature solution method. The structure details of these crystals are determined by X-ray crystallographic analysis and Raman spectroscopy. It is observed that the crystal consists of LuVO4 phase with trace amount of imperfections possibly due to oxygen vacancies. The optical quality of the crystal is assessed by Spectroscopic Ellipsometry (SE). The crystal shows higher than +0.2 birefringence in a large interval of wavelengths.