De Gao Zhong

The Synthesis and Purification of 4-Dimethylamino-N-Methyl -4-Stilbazolium Tosylate

4-dimethylamino-N-methyl -4-stilbazolium tosylate(DAST) was synthesized by the condensation and ion exchange reaction of 4-methyl-N-methyl pyridinium tosylate, 4-N,N-dimethylamino -benzaldehyde and silver p-toluenesulfonate, the reaction procedure was easy with high efficiency. The purity of the product was further improved by successive abstersion and recrystallization. The powder was investigated by Fourier transform infrared spectrum, nuclear magnetic resonance and elemental analysis. The results showed that the quality of the powder as crystal raw material was very high, the product could meet the requirements for crystal growth, the procedure of washing the product by chloroform was important to achieve the high quality.

In Situ Observation of the Growing Surface Morphology of KDP Crystals by Microscope

A kind of in-situ crystal growth observation system for solution temperature reduction method was designed. The growth surface morphology of KDP crystal was observed by this system. Dislocation hillocks with elliptical shape were clearly distinguished on the {100} face. The dynamics process of morphology evolvement on growth surface of KDP crystals was recorded and analyzed. The growth velocity of the step trains generated from dislocation hillocks was about ~10-4.

Synchrotron-radiation X-ray Topography of the Rapid Grown KDP Crystals

KDP crystals were rapidly grown from point seeds by temperature reduction method. White-beam synchrotron radiation X-ray topography was used to study the growth imperfections in KDP crystals. Strong dislocation bunches originate on the prismatic faces of the seed were found. The producing reason of these dislocation bunches was discussed. Sector boundary between the prismatic sector and pyramid sector caused by the unbalance distribution of trivalent metal ions were also observed and analyzed.

ADP Single Crystal Growth from Solution in Defined Crystallographic Direction

The method of growing ADP crystal along {100} direction rapidly has been studied. A platform was used to grow ADP crystal to improve its utilization and optical quality. Chemical etching was used to analyze the dislocation mechanism. It indicates that the crystal grown in the defined crystallographic direction {100} could be qualified for optical application. The grown crystals were characterized by optical transmission spectra. It can be observed that the transmittance of the sample grown by our method reached 85% in the visible region.

Crystal Growth and Optical Spectroscopy of Ytterbium-Doped Lutetium Orthophosphate

The flux growrh method is employed to grow the Yb:LuPO4 crystal using lead pyrophosphate Pb2P2O7 as the high-timperature solvent. The infrared spectroscopy(IR) was tested to determine the purity of the obtained crystal. The absorption spectra of the 5% Yb-doped Yb:LuPO4 crystal was measured at room temperature. Three absorption peaks that located on 985nm, 976nm and 953nm were found, and the absorption cross sections on the absorption peaks were calculated respectively. The results shows that Yb:LuPO4 crystal has potential to be applied as laser material.

Growth and Thermal Characterization of Yb:Y0.923Lu0.071VO4

A new mixed laser crystal, Yb0.006Y0.923Lu0.071VO4, has been successfully grown using the Czochralski method. X-ray powder diffraction analysis shows that the crystal has ZrSiO4 structure. Density, thermal expansion coefficients, specific heat and thermal diffusion coefficients were measured, and the thermal conductivity coefficients were determined.

A Simplified Method of Synthesis and Purification of 4-Dimethylamino-N-Methyl -4-Stilbazolium Tosylate

DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate) crystal material was synthesized and purified by a relatively simple method. The synthesis process was easy to operate experimentally and the cost of raw materials can be cut down. The purification process was much easier than the previously published method. Fourier transform infrared spectrum (FTIR) was used to analyze the functional group of raw material and no extra functional groups were found. Nuclear magnetic resonance (NMR) study was performed to identify the different modes presented in the compound. The results showed that the quality of the prepared crystal raw material could meet the requirements on crystal growth. DAST crystals were grown from the synthesized raw material by slowly cooling method. The crystal structure was characterized by X-ray diffraction (XRD) study and the results showed that the crystal grown from the synthesized raw material was the same as that grown from pure DAST crystal raw material.

Vickers Hardness Studies on (001) and (110) Faces of DAST Crystal

4-Dimethylamino-N-methyl 4-Stilbazolium Tosylate（DAST） crystals were prepared by the slope nucleation method. The Vickers hardness of DAST crystal was studied on (001) and (110) faces. It was found that the Vickers hardness increases with increasing load and the Hv on (001) face is higher than that on (110) face. The values of Meyer’s index number n and hardness were calculated from Hv. The results showed that the DAST crystals belong to the soft material category.

Surface Morphology and Shape Analysis of Nonlinear Optical Crystal DAST

DAST (4-N, N-dimethylamino-4′-N′-methyl stilbazolium tosylate) crystal has been grown by slope nucleation method (SNM) at different cooling rates (0.5°С/d and 0.1°С/d). The morphology of crystal growing surfaces was observed by scanning electron microscope (SEM) and microscope. Different growth striations were found on the growth surfaces. The arrangements of crystal ions and cooling rate have a great influence on the crystal shape. The relationship between the DAST crystal molecular structure and the crystal shape was systematically studied by analyzing the growing surface morphology. Two-dimensional nucleation mechanism was found on growing faces with increasing supersaturation.

The Surface Morphology and Mechanical Behavior Studies of DAST Crystal on (001) and (110) Faces

4-dimethyla-mino-N-methyl 4-stilbazolium tosylate（DAST） crystals were prepared by the slope nucleation method (SNM). The structural and optical properties of the grown crystals were studied by employing powder XRD and FIIR. The surface morphology of DAST crystals was observed by scanning electron microscope (SEM). The Vickers hardness studies were carried out on (001) and (110) faces of grown DAST crystal. The values of Meyer’s index number n and hardness were calculated from Hv. The results showed that the DAST crystals belong to the soft material category.