Physicochemical properties and theoretical explanation of ZnCd(SCN)4 crystal

The crystal density and Mohs hardness of zinc cadmium thiocyanate (ZCTC), ZnCd(SCN)₄ have been measured at room temperature. The specific heat of the crystal is 699.5 J mol⁻¹ K⁻¹ at 300 K. The thermal expansion coefficient (TEC) along the a and c axes, respectively, is interpreted on the basis of crystal structure. The thermal decomposition process is characterized by thermogravimetry analysis and differential scanning calorimetry (TGA/DSC). The intermediates and final products of the thermal decomposition were identified by X-ray powder diffraction at room temperature. The high-temperature effect in air on the optical transmission of the crystal was also studied.     

Growth and optical properties of Er,Yb:YAl3(BO3)4 crystal

Single crystal of erbium, ytterbium-codoped yttrium aluminum tetraborate Er,Yb:YAl₃(BO₃)₄(Er,Yb:YAB) has been grown by the flux method. The absorption spectrum in the visible and NIR regions of Er,Yb:YAl₃(BO₃)₄ crystal are measured at room temperature and fluorescence spectrum of Er,Yb:YAl₃(BO₃)₄ crystal are also measured at room temperature, excited by 976 nm laser. Not only the strong NIR emission peaks located at 1548 nm was observed, but also the visible up-conversion luminescence has been found. The specific heat of the Er/Yb:YAB crystal at room temperature is 0.81 J/g °C.     

Crystal growth and spectral properties of Pr:La2(WO4)3

Pr³⁺-doped La₂(WO₄)₃ single crystal with dimensions up to Ø 20 mm × 35 mm has been grown by the Czochralski method. The structure of the Pr³⁺:La₂(WO₄)₃ crystal was determined by the X-ray powder diffraction and the Pr³⁺ concentration in this crystal was determined. The absorption and fluorescence spectra of Pr³⁺:La₂(WO₄)₃ crystal were measured at room temperature, and the fluorescence lifetime of main emission multiplets were estimated from the recorded decay curves. The spectral properties related to laser performance of the crystal were evaluated.     

Growth, thermal and optical properties of Yb:GdYAl3(BO3)4 crystal

Single crystal of Yb:GdYAl₃(BO₃)₄(Yb:GdYAB) has been grown by the flux method. The structure of Yb:GdYAB crystal has been determined by X-ray diffraction analysis. The experiment show that the crystal has the same structure as that of YAl₃(BO₃)₄ crystal and its unit cell constants have been measured to be a = 9.30146 Å, c = 7.24164 Å, Vol = 542.59 Å³. The absorption and fluorescence spectrum of Yb:GdYAl₃(BO₃)₄ crystal have also been measured at room temperature. In the absorption spectra, there are two absorption bands at 938 nm and 974 nm, respectively, which is suitable for InGaAs diode laser pumping. In the fluorescence spectra, there are two fluorescence peaks at 992 and 1040 nm. The thermal properties of Yb:GdYAl₃(BO₃)₄ crystal have been studied for the first time. The thermal expansion coefficient along c-axis is almost 5.4 times larger than that along a-axis. The specific heat of the crystal has been measured to be 0.77 J/g °C at room temperature. The calculated thermal conductivity is 5.26 Wm⁻¹ K⁻¹ along a-direction.     

Spectral properties of Tm:NaGd(MoO4)2 crystal

The Tm³⁺:NaGd(MoO₄)₂ crystal with dimensions of Φ 15 × 38 mm² was grown by Czochralski method. Polarized absorption and fluorescence spectra at room temperature were investigated. The absorption bands attributed to ³H₆ → ³H₄ transition have large absorption cross-sections, which are 3.99 × 10⁻²⁰ and 2.36 × 10⁻²⁰ cm² for σ- and π-polarization, respectively. The emission bands corresponding to the ³H₄ → ³H₆ transition are strong and broad with emission cross-sections of 1.33 × 10⁻²⁰ and 1.20 × 10⁻²⁰ cm² for σ- and π-polarization, respectively. The correlative full widths at half maximum are 35 nm for σ-polarization and 36 nm for π-polarization. The fluorescence lifetime for the ³H₄ → ³F₄ transition is 146 μs and the luminescent quantum efficiency is 76.8%.     

Growth and properties of Ca0.28Ba0.72Nb2O6 single crystals

Calcium barium niobate Ca_0.28Ba_0.72Nb₂O₆ (CBN-28) crystals were successfully grown by the Czochralski method. X-ray powder diffraction experiments indicated that CBN single crystals are tetragonal with a = 12.432(±0.002) Å and c = 3.957(±0.001) Å, which have almost the same structure as the Sr_0.50Ba_0.50Nb₂O₆ (SBN-50) crystal. The thermal expansion coefficient perpendicular to Z-direction had been measured to be 1.25 × 10⁻⁵ K⁻¹ between 293.15 and 572.15 K, and along Z-axis was negative between 298.15 and 543.15 K. The specific heat of the crystal had been measured by the differential scanning calorimetric experiments. The transmittance spectra from 200 to 3200 nm were also measured. The measured temperature dependence of dielectric constants showed that the Curie temperature of the CBN-28 crystals is 260 °C, which is about 200 °C higher than that of the (SBN) crystal.     

Synthesis and upconversion luminescence properties of Yb/Er codoped BaGd2(MoO4)4 powder

Synthesis and upconversion luminescence properties of the new BaGd₂(MoO₄)₄:Yb³⁺,Er³⁺ phosphor were reported in this paper. The phosphor powder was obtained by the traditional high temperature solid-state method, and its phase structure was characterized by the XRD pattern. Based on the upconversion luminescence properties studies, it is found that, under 980 nm semiconductor laser excitation, BaGd₂(MoO₄)₄:Yb³⁺,Er³⁺ phosphor exhibits intense green upconversion luminescence, which is ascribed to ²H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 transition of Er³⁺. While the observed much weaker red emission is due to the non-radiative relaxation process of ⁴S_3/2 → ⁴F_9/2 and ⁴F_9/2 → ⁴I_15/2 transition originating from the same Er³⁺. The concentration quenching effects for both Yb³⁺ and Er³⁺ were found, and the optimum doping concentrations of 0.5 mol% Yb³⁺ and 0.08 mol% Er³⁺ in the new BaGd₂(MoO₄)₄ Gd³⁺ host were established.     

Negative thermal expansion in Th2O(PO4)2

High temperature X ray diffraction performed on recently discovered orthorhombic Th₂O(PO₄)₂ shows a continuous linear thermal contraction (−1.6 × 10⁻⁶ °C⁻¹) in 20–600 °C range and a near-zero expansion at higher temperatures resulting from a dual structural deformation involving oxygen oscillations and inter-cations repulsions. Although similar mechanisms were observed in isotypic Zr₂O(PO₄)₂ (+1.5 × 10⁻⁶ °C⁻¹) and U₂O(PO₄)₂ (−1.4 × 10⁻⁶ °C⁻¹), those observed in Th₂O(PO₄)₂ are particularly intense because of the high ionic radius of tetravalent thorium.     

Growth, thermal and mechanical properties of new nonlinear optical barium bis-paranitrophenolate paranitrophenol tetrahydrate single crystal

Barium bis paranitrophenolate paranitrophenol tetrahydrate, a new semiorganic nonlinear optical single crystal has been grown by slow evaporation solution growth technique at room temperature of 30 °C. Crystal of dimensions of 29 mm × 11 mm × 5 mm was obtained in a period of 30 days. X-ray diffraction analysis reveal the newness of the crystal structure belonging to the orthorhombic class with lattice parameters a = 19.899(5) Å, b = 28.019(8) Å, c = 10.745(4) Å and α = β = γ = 90°. The grown crystal is examined for its nonlinear optical nature with Kurtz powder technique after being sieved for particle sizes between 5 and 100 μm and analyzed for its thermal and mechanical properties. The effective nonlinear optical coefficient being 16 times greater than that of KDP crystal, good thermal stability up to 120 °C with the Meyer's constant n < 2 helps fashion the crystal towards device geometry.     

Crystal data and indirect optical transitions in Tl2InGaSe4 crystals

The room temperature crystal data and the optical properties of the Bridgman method grown Tl₂InGaSe₄ crystals are reported and discussed. The X-ray diffraction technique has revealed that Tl₂InGaSe₄ is a single phase crystal of monoclinic structure. The unit cell lattice parameters, which were recalculated from the X-ray data, are found to be a = 0.77244 nm, b = 0.64945 nm, c = 0.92205 nm and β = 95.03°. The temperature dependence of the optical band gap of Tl₂InGaSe₄ single crystal in the temperature region of 290–500 K has also been investigated. The absorption coefficient was calculated from the transmittance and reflectance data in the incident photon energy range of 1.60–2.10 eV. The absorption edge is observed to shift toward lower energy values as temperature increases. The fundamental absorption edge corresponds to indirect allowed transition energy gap of 1.86 eV that exhibited a temperature coefficient γ = −3.53 × 10⁻⁴ eV/K.     

Larger Ba(NO3)2/Sr(NO3)2 crystal growth and solubility determination

The solubility of Ba(NO₃)₂ and Sr(NO₃)₂ crystals in aqueous solution from 25 to 65 °C has been determined by both an optical interferometer and a weight technique. A Mach-Zehnder interferometer was used for measuring the concentration distribution of Ba(NO₃)₂ and Sr(NO₃)₂ near the solid/liquid interface during crystal growth and dissolution. A fringe carrier technique was introduced to visualize more clearly the boundary layer and to solve the concentration distribution. Crystals were successfully grown with sizes larger than  mm by a temperature cooling method. The Ba_xSr_1−x(NO₃)₂ crystal was also nucleated and grown. The Raman spectra of Ba_xSr_1−x(NO₃)₂ indicate that the barium ions probably degrade the properties of Sr(NO₃)₂.     

Effect of the cooling rate on the thermoelectric properties of p-type (Bi0.25Sb0.75)2Te3 and n-type Bi2(Te0.94Se0.06)3 after melting in the bismuth-telluride system

The p-type (Bi_0.25Sb_0.75)₂Te₃ and n-type Bi₂(Te_0.94Se_0.06)₃ ingots were prepared by cooling at various cooling rates C after melting so that they have an intermediate state between the polycrystalline and Bridgman ingots which lowers their thermal conductivity κ, where C was changed from 0.10 to 2375 K/min in an evacuated glass tube. When the ingots were cooled at C = 0.50 K/min under the uniaxial temperature gradient of 5 K/cm, it was observed that the c axis of some grains points to the freezing direction. The electrical resistivity ρ, Seebeck coefficient α and κ of ingots were measured at 298 K along the freezing direction, so that ρ and κ at C = 0.50 K/min were lower by 20-30% and 9% than those of the corresponding Bridgman ingots. The thermoelectric figure of merits ZT(=α²T/ρκ) estimated for the p- and n-type ingots then reached high values of 1.27 and 1.25 at 298 K, respectively.     

Synthesis, crystal structure and magnetic properties of a new lithium cobalt metaphosphate, LiCo(PO3)3

A new lithium cobalt metaphosphate, LiCo(PO₃)₃, is reported for the first time, which was discovered during the exploratory synthesis in Li-Co-P-O system by solid state reaction. The structure has been refined by powder X-ray Rietveld refinement method (P2₁2₁2₁, a = 8.5398(2) Å, b = 8.6326(2) Å and c = 8.3520(2) Å, Z = 4, R_p = 13.6%, R_wp = 19.4%, R_exp = 17.7%, S = 1.11, χ² = 1.23). It is isostructural with LiM(PO₃)₃ (M = Fe, Cu). It contains (PO₃)¹⁻ chains with the Co atoms localized in the octahedral sites, bridging four neighboring chains. The magnetic susceptibility measurement showed a typical paramagnetic behavior of high spin of Co²⁺, following the Curie-Weiss law in the temperature range of 5-300 K. Unlike the olivine type lithium cobalt phosphate, LiCoPO₄, cyclic voltammetry of LiCo(PO₃)₃ assembled in the coin-type cell showed no electrochemical activity in the voltage region of 1-5 V versus Li/Li⁺.     

Growth and characterization of non-linear optical crystal Cd3Zn3B4O12

Cd₃Zn₃B₄O₁₂ polycrystals were synthesized by solid-state and wet chemical reaction methods. Cd₃Zn₃B₄O₁₂ single crystals with millimeter grade were grown from the self-flux B₂O₃ (Cd:Zn:B = 1:1:1.5); and larger crystals were obtained from the PbO-0.85PbF₂ fluxes easily. As-grown crystals were characterized by differential scanning calorimetry and thermogravimetric, X-ray diffraction, infrared and Raman spectral analysis, respectively. The non-linear optical coefficient of the Cd₃Zn₃B₄O₁₂ crystal is 2.6 times as large as that of KH₂PO₄ crystal. Chemical etching shows that this crystal is very stable in neutral solution and not hygroscopic in air at room temperature.     

High temperature thermoelectric properties of (Ca, Ce)4Mn3O10

Thermoelectric (TE) properties such as resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) of Ca_4−3xCe_3xMn₃O₁₀ (0<x≤0.03) polycrystalline samples were measured from room temperature to 1000 K. ρ shows an obvious decrease with the increment of Ce content. The hopping conduction mechanism is used to explain the conduction behavior of these samples. The negative S values indicate that these materials are n-type. The sample of x=0.03 has the largest power factor, 0.52×10⁻⁴ Wm⁻¹ K⁻² at 1000 K. The value of κ and the dimensionless figure of merit of this sample is 1.51 Wm⁻¹ K⁻¹ and 0.034 at 1000 K, respectively.     

Enhanced luminescence by charge compensation in red-emitting Eu-activated Ca3Sr3(VO4)4

The effects of charge compensation on the luminescence behavior of a red-emitting phosphor, Ca₃Sr₃(VO₄)₄:Eu³⁺, were investigated. It has been observed that charge compensated by monovalent ions, especially Na⁺, shows greatly enhanced red emission under ultraviolet excitation. It is found that Na₂CO₃ addition acts as a fluxing agent and plays a role in charge compensation, which clearly improves the emission intensity of Eu³⁺-activated Ca₃Sr₃(VO₄)₄. Enhanced emission intensity of the corresponding charge compensated phosphors under ultraviolet radiation may find application in the production of red phosphors for white light-emitting diodes.     

蓝紫光倍频晶体ZCTC晶体生长与透过性质研究

硫氰酸锌镉（ZnCd(SCN）4），简称ZCTC，是自行研发的一种蓝紫光倍频晶体。通过恒温蒸发溶液来生长ZCTC晶体，测量了KSCN和ZCTC溶液的透过率曲线，发现SCN^-基因是影响ZCTC晶体紫外截止波长的主要因素。研究还发现ZCTC晶体（100）面的透过度更高于（001）面，通过化学镀膜可以减少晶体表面反射损耗。ZCTC晶体经180℃，24h烘烤后，在300-800nm之间透过率明显下降。     

Synthesis and characterization of a new organic dihydrogenomonophosphate [3,5-(CH3O)2C6H3NH3]2(H2PO4)2

Chemical preparation, crystal structure, calorimetric studies and spectroscopic investigation are given for a new organic cation dihydrogenomonophosphate [3,5-(CH₃O)₂C₆H₃NH₃]₂(H₂PO₄)₂. This compound is triclinic with the following unit cell parameters: a=9.030(6) Å, b=16.124(5) Å, c=8.868(3) Å, α=75.04(3)°, β=110.71(4)°, γ=104.61(1)°, Z=4, V=1148.0(1) Å³, Z=2 and ρ_cal.=1.454 g cm⁻³. Crystal structure was solved and refined to R=0.04, 2752 independent reflections. The atomic arrangement can be described as inorganic layers of H₂PO₄⁻ anions parallel to planes, between which are located the organic groups. Solid-state and MAS-NMR spectroscopies are in agreement with the X-ray structure. Ab initio calculations allow the attribution of the phosphorous and carbon signals to the independent crystallographic sites and to the various atoms of the organic groups.     

One-dimensional lone electron pair micelles in the crystal structure of Pb5(SiO4)(VO4)2

The structure of Pb₅(SiO₄)(VO₄)₂ (hexagonal, P6₃/m, a = 9.9865(11), c = 7.3599(12) Å, V = 635.67(14) Å³, Z = 2) has been solved by direct methods and refined to R₁ = 0.051 on the basis of 440 unique observed reflections with |F_o|≥4σ_F. The compound belongs to the apatite structure type. The Pb coordination polyhedra are distorted due to the presence of stereoactive lone electron pairs Ψ. The structure contains channels running along the c axis and centered at (00z). The channels are most probably occupied by the lone electron pairs of the Pb²⁺ cations and thus represent lone electron pair micelles. The existence of such micelles in the structure may well be the reason for the electrogyratory effect and protonic conductivity observed in crystals of the title compound.