Xiulan Duan

Preparation and Characterization of Nonlinear Optical Crystal Materials: Cadmium Mercury Thiocyanate and its Lewis Base Adducts

Cadmium mercury thiocyanate (CdHg(SCN) 4 , CMTC) and its two lewis base adducts: cadmium mercury thiocyanate dimethyl-sulphoxide (CdHg(SCN) 4 (H 6 C 2 OS) 2 , CMTD) and cadmium mercury thiocyanate glycol monomethyl ether (CdHg(SCN) 4 (C 3 H 8 O 2 ), CMTG) have been discovered as nonlinear optical (NLO) crystal materials. Their structural, optical and physicochemical properties were characterized by X-ray powder diffraction (XRPD), infrared spectroscopy, vis/UV/NIR spectra and thermal analysis. It is discovered that their transparency cutoffs lie in the UV region and CMTD crystals possess the shortest cutoff wavelength among the three crystal materials.

Physicochemical behavior of nonlinear optical crystal CdHg(SCN)4

Abstract The preparation and purification of cadmium mercury thiocyanate, CdHg(SCN)4 (CMTC) are described. The identity of the synthesized compound was characterized by Raman, infrared and X-ray powder diffraction spectra. The thermal stability and thermal decomposition of CMTC crystals were investigated by means of thermogravimetric analysis and differential scanning calorimetry. The impurities in the growth solutions and their effects are discussed.

Cation distribution in co-doped ZnAl2O4 nanoparticles studied by X-ray photoelectron spectroscopy and 27Al solid-state NMR spectroscopy.

Co(x)Zn(1-x)Al(2)O(4) (x = 0.01-0.6) nanoparticles were synthesized by the citrate sol-gel method and were characterized by X-ray powder diffraction and transmission electron microscopy to identify the crystalline phase and determine the particle size. X-ray photoelectron spectroscopy and (27)Al solid-state NMR spectroscopy were used to study the distribution of the cations in the tetrahedral and octahedral sites in Co(x)Zn(1-x)Al(2)O(4) nanoparticles as a function of particle size and composition. The results show that all of the as-synthesized samples exhibit spinel-type single phase; the crystallite size of the samples is about 20-50 nm and increases with increasing annealing temperature and decreases with Co-enrichment. Zn(2+) ions are located in large proportions in the tetrahedral sites and in small proportions in the octahedral sites in Co(x)Zn(1-x)Al(2)O(4) nanoparticles. The fraction of octahedral Zn(2+) increases with increasing Co concentration and decreases with increasing particle size. Besides the tetrahedral and octahedral coordinations, the presence of the second octahedrally coordinated Al(3+) ions is observed in the nanoparticles. The change of the inversion parameter (2 times the fraction of Al(3+) ions in tetrahedral sites) with Co concentration and particle size is consistent with that of the Zn fraction in octahedral sites. Analysis of the absorption properties indicates that Co(2+) ions are located in the tetrahedral sites as well as in the octahedral sites in the nanoparticles. The inversion degree of Co(2+) decreases with increasing particle size.

Absorption and photoluminescence characteristics of Co2+:MgAl2O4 nanocrystals embedded in sol–gel derived SiO2-based glass

Abstract Co 2+ :MgAl 2 O 4 nanocrystals embedded in SiO 2 -based glass have been prepared by heating the gels of composition 5MgO–6Al 2 O 3 –89SiO 2 – x CoO ( x =0.2, 0.4, 0.6, 1.0) (mol%). When the gel samples were heated up to 1000 °C, MgAl 2 O 4 nanocrystals were precipitated and Co 2+ ions were located in the tetrahedral sites in MgAl 2 O 4 nanocrystals. X-ray diffraction analysis shows that the diameter of MgAl 2 O 4 crystal is ∼5–15 nm. Absorption and emission bands in the visible and near infrared regions have been observed from transparent Co 2+ :MgAl 2 O 4 /SiO 2 nanocomposites. The observed absorption and emission spectra are characteristic of tetrahedral Co 2+ in crystals. The intensity of absorption bands increases with the increasing of heat-treatment temperature and Co 2+ concentration, while with the increasing of Co 2+ concentration, the fluorescence intensity decreases and the fluorescence spectra in the visible range show a red shift. The crystal field parameter D q of 405 cm −1 and the Racah parameters B of 752 m −1 and C of 3388 cm −1 were calculated for tetrahedral Co 2+ ions.

Spectroscopic and thermal behavior of ZnHg(SCN)4

Abstract The synthesis and purification of zinc mercury thiocyanate, ZnHg(SCN)4 (ZMTC), are described. The identity of the synthesized compound was characterized by elemental analysis, X-ray powder diffraction, infrared, Raman, and UV/Vis/NIR transmission spectra. The thermal stability and thermal decomposition of ZMTC crystal were investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements. The intermediates and final products of the thermal decomposition were identified by X-ray powder diffraction (XRPD).

Investigation of the dielectric and piezoelectric properties of ReCa4O(BO3)3 crystals

Piezoelectric ReCa4O(BO3)3 (ReCOB, Re: rare earth) crystals, including ErCOB, SmCOB, PrCOB and LaCOB, were successfully grown by the Czochralski (Cz) method. The dielectric constants were determined to be , and for ErCOB, , and for SmCOB, , and for PrCOB, , and for LaCOB, respectively. The electromechanical coupling factors k26 and piezoelectric coefficients d26 were found to be 18.5% (7.6 pC N−1), 27.0% (12.7 pC N−1), 31.5% (15.8 pC N−1) and 25.0% (11.8 pC N−1) for ErCOB, SmCOB, PrCOB and LaCOB crystals, respectively. The dielectric and piezoelectric properties as a function of Re3+ ion radius were studied, with maximum values being observed in the PrCOB crystals, due to the similar ion radius of Pr3+ and Ca2+. The relationship between the structure and dielectric/piezoelectric properties of ReCOB crystals was explored, to further optimize the dielectric and piezoelectric properties in ReCOB series crystals.

Transparent cobalt doped MgO–Ga2O3–SiO2 nano-glass-ceramic composites

Transparent cobalt doped MgO–Ga2O3–SiO2 nano-glass-ceramic composites were prepared from Si, Ga, Mg, and Co molecular precursors by a sol-gel method. X-ray diffraction patterns and transmission electron microscopy showed that the resulting material is composed of an amorphous silicate network that encloses nanocrystalline MgGa2O4 particles. Analysis of the absorption and luminescence properties indicates that Co ions are, at least partially, trapped in the crystalline phase and located in tetrahedral sites in MgGa2O4 nanocrystals. The absorption section was calculated to be 1.15×10−19cm2.

Crystal growth and characterization of a new organometallic nonlinear-optical crystal material: MnHg(SCN)4(C3H8O2)

A potentially useful second harmonic generation (SHG) organometallic nonlinear-optical crystal: manganese mercury tetrathiocyanate glycol monomethyl ether, MnHg(SCN) 4 (C 3 H 8 O 2 ) (MMTG) has been prepared, and high optical quality single crystals have been successfully grown by the slow temperature-lowering technique. Its structural, physicochemical and optical properties are characterized by elemental analyses, infrared spectroscopy, transmission electron microscopy (TEM), X-ray powder diffraction, thermal analysis, powder SHG measurements and Vis/UV/NIR spectroscopy. The results of characterizations have shown that MMTG possesses good physicochemical stabilities up to 145 °C, exhibits powder SHG efficiencies close to that of urea. The UV transparency cutoff is 375 nm, and the transmission is 33.54% at 404 nm, the sample thickness was 2.76 mm, which is 6% greater than that of MnHg(SCN) 4 (MMTC).

A systematic spectroscopic study of four bimetallic thiocyanates of chemical formula AB(SCN)4: ZnCd(SCN)4 and AHg(SCN)4 (A=Zn, Cd, Mn) as UV nonlinear optical crystal materials

Abstract Bimetallic thiocyanate complexes of chemical formula AB(SCN)4(ABTC): ZnCd(SCN)4 and MHg(SCN)4 (M=Zn, Cd, Mn) were discovered as potentially useful crystal materials in ultraviolet second-harmonic generation. The structures of these compounds were derived from powder X-ray diffraction data, and unit-cell parameters were calculated by the TREOR program. Their vibrational spectra were studied by Raman spectroscopy, which show that the characteristic vibrational modes of AB(SCN)4 crystals arise mainly from the internal vibrations of the SCN, A(NCS)4, and B(SCN)4 clusters. The reason of the high optical nonlinearities of ABTC crystals has been studied by the use of the Raman spectra and the molecular orbital theory: the distorted A(NCS)4 and B(SCN)4 tetrahedra and the conjugated charge-transfer (–A–NCS–B–) bridges that connect all the distorted tetrahedra together.

Investigation on the Aqueous Solution for Growth of Bimetallic Thiocyanate Complex Crystal Materials

The stability of cadmium mercury thiocyanate (CMTC) crystal growth solution was mainly discussed. The effects of temperature, pH value, time and KCl concentration on CMTC crystal growth were investigated. The effects of pH value and KCl concentration on crystallization habit of CMTC were also studied. The results show that when pH value ranges from 2.5 to 3.8, the solution is relatively stable, under the condition of pH < 2.0 or pH ≥ 4.0, the solution has poor stability and some powder appears. The solution becomes unstable at high temperatures. When the concentration of KCl is more than 27% there has not generated CMTC crystal in the solution, a new kind of material produced from solution. The pH value and KCl concentration affect crystalline morphology of CMTC crystal.