Caina Luan

Growth and thermal properties of tri-allylthiourea cadmium chloride (ATCC) crystal

Abstract The tri-allylthiourea cadmium chloride crystal grown was characterized by recording the powder X-ray diffraction pattern and indexing the diffracting planes. The thermal expansion coefficients along a - and c -axes are 2.19×10 −5 and 6.15×10 −5 xa0K −1 , respectively. The specific heat of the crystal was measured to be 590.43xa0J/molxa0K at 293.15xa0K. The thermal decomposition process was analyzed according to the result of differential thermal analysis and PXRD patterns of residues at different temperatures.

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.

The growth and properties of Ca3TaGa3Si2O14 single crystals

Abstract We have successfully grown a new ordered langasite structure piezoelectric single crystal Ca3TaGa3Si2O14 (CTGS) using the Czochralski (CZ) method. The single crystal structure was investigated by X-ray powder diffraction (XRPD) experiments and showed that the CTGS single crystals had a single phase and had the same structure as the La3Ga5SiO14 (LGS) crystal. The transmittance spectra from 190 to 3200xa0nm were measured and the transmittance of CTGS crystal was about 85% above 350xa0nm. The specific heat of the crystal has been measured to be 0.52xa0J/gxa0K at room temperature. The thermal expansion coefficients perpendicular and parallel to Z direction has been measured to be 5.2×10−6 and 3.7×10−6/K between 298.15 and 450xa0K by a thermomechanical analyzer (TMA).

Growth and characterization of Sr3NbGa3Si2O14 single crystals

Abstract A new ordered langasite structure piezoelectric single crystal Sr3NbGa3Si2O14 (SNGS) was grown by using the Czochralski method. The single crystal structure was investigated by X-ray powder diffraction experiments and shown to be a single phase and have the same structure as the La3Ga5SiO14 crystal. The chemical composition of the grown crystal was measured by X-ray fluorescent analysis. The transmittance spectra from 190 to 3200xa0nm were measured. The melting point of SNGS crystal and raw materials were measured.

Sol–gel preparation of Co2+: MgAl2O4 nanocrystals embedded in SiO2-based glass

Abstract Co 2+ : MgAl 2 O 4 nanocrystals embedded in SiO 2 -based glass were prepared by a sol–gel method for the first time. The gels of composition 89SiO 2 -5.9Al 2 O 3 -4.9MgO-0.2CoO (MAS) were prepared at room temperature, and heat-treated in the temperature range 1000–1100°C for 5 or 10xa0h in air to induce crystallization of MgAl 2 O 4 spinel. Co 2+ ions were located in tetrahedral sites in MgAl 2 O 4 nanocrystals. The size of Co 2+ : MgAl 2 O 4 crystal is estimated to be 12xa0nm according to X-ray powder diffraction and transmission electron microscope studies. The absorption and emission spectra of the heated samples were presented. The crystal field parameter D q of 405xa0cm −1 and the Racah parameters B of 752xa0m −1 and C of 3388xa0cm −1 were calculated for tetrahedral Co 2+ ions.