Zhang-Shou Gao

Effect of EDTA on the light scatter in KDP crystal

KDP crystals with different concentrations of EDTA in solution were grown. Light scatter was detected with ultramicroscopic method. It has been proven that light scatter in KDP crystal aggravates with the increasing concentration of EDTA in the growth solution. The increase with light scatter occurs since EDTA inhibits the growth of KDP crystal at high concentration, which results in the formation of mother liquid inclusions, which in turn causes light scatter. The density, size and shape of light scatter are varied within different sectors of the KDP crystal. The mechanism of the effect is discussed.

The effects of anionic impurities on the growth habit and optical properties of KDP

Abstract Some anionic impurities (sodium metaphosphate, potasium pyrophosphate, formic acid, acetic acid, oxalic acid and tyrosine) were found to have an inhibiting effect on the growth of KDP crystals. Complete stoppage of pyramidal face growth was observed in the presence of high concentration of both [H x − n (PO 3 ) x ] n − and [H 2 P 2 O 7 ] 2− , and in these cases the crystal habit was changed into a closed octahedron and the whole crystal stopped growing. It was proposed that the inhibition is caused by the adsorption of the anions at the growing crystal surface, especially the pyramidal surface through the formation of H-bond between the anions and the H 2 PO 4 − groups. The anions have a harmful effect on the laser damage threshold due to possible incorporation.

Polymorphism and metastable growth of DKDP

Abstract Single crystal K ( H 1− x D x ) 2 PO 4 , DKDP or deuterated pottassium dihydrogen phosphate in the low temperature tetragonal form is desired as single crystals for electro-optic applications. Its growth by slow cooling of aqueous solutions is limited by the fact that the temperature interval for cooling is usually limited by the upper temperature set by the tetragonal-monoclinic transition. The dependence of the transition temperature on deuterium concentration in solution has been studied. Careful studies showed that at moderate conditions of supersaturation the metastable tetragonal form persists and can be crystallized in the monoclinic stability field. These results were used to allow growth of good quality crystals over an extended temperature interval including the monoclinic stability region.

Effects of anions on rapid growth and growth habit of KDP crystals

Abstract The synthesis of KDP from its raw material has been found exist in the growth solution. In the crystal growth experiment, significant extension of specific faces was observed at low dopant concentration. At high doping concentration, the growth rate of the whole crystal decreased with no significant habit modification. The inhibiting effects of phosphite and other H-bonding anionic ions on the growth of pyramidal faces are discussed. Rapid growth rate experiments have been carried out with purified material and an averaged growth rate of 18.6mm/day was obtained.

Study on the liquid inclusion induced light scatter in KDP crystal

In this paper we describe the formation of liquid inclusion induced light scatter in potassium dihydrogen phosphate crystal. The measurements were done by ultra-microscopy, TEM and AFM. The dimension of the scatter and the composition have been measured and a mechanism formation of the liquid inclusion induced scatter is proposed and discussed.

Cluster Formation in Solid–Liquid Interface Boundary Layers of KDP Studied by Raman Spectroscopy

The cluster formations in solid-liquid interface boundary layers of KDP crystals have been studied by Raman spectroscopy and ab initio cluster calculations with the density-functional theory. The calculations are made on H 2 PO 4 , H 4 P 2 O 8 , and H 4 P 4 O 16 clusters, which model the cluster structure in different growth layers. Excellent agreement has been achieved between vibrational frequencies predicted by theory and those observed in experiments. The present results also show that the desolvation process of polymer clusters takes place within the characteristic boundary layers. The growth unit of crystal growth is identified as H 4 P 2 O 8 dimer cluster.

Study on K(DxH1-x)2PO4 Crystals: Growth Habit, Optical Properties and their Improvement by Thermal-Conditioning

Phosphite, which often exists in growth solutions obtained directly from commercial P 2 O 5 , was found to have significant inhibiting effects on the growth of pyramidal face of KDP crystals. K(D x H 1-x ) 2 PO 4 (referred to as DKDP) crystals with different deuterium fraction x were grown and the optical performances were investigated. The absorption coefficients at 1.05 μm decreases monotonically with the increase of x. The transmission threshold shift from 1.65μm at x=0 to 2.10 μm at x=0.96. The high temperature phase transition temperature and latent heat were measured using the method of differential scanning calorimetry (DSC). Thermal conditioning experiments were carried out at 180°C and 140°C for KDP and DKDP, respectively. After conditioning, a different degree of improvement was observed in the optical homogeneity of the samples, while the laser damage threshold and light absorption coefficient showed no significant change.

The reason of causing of light scatter in pyrophosphate doped KDP crystal and its elimination

Pyrophosphate doped KDP crystal was grown from aqueous solution by the temperature lowering method. Light scatter in KDP crystal was detected with an ultramicroscopic method. It has been proved that light scatter in KDP crystal aggravated when pyrophosphate was doped into the growth solution, which distributed non-uniformly in prism and pyramidal sectors of the KDP crystal. The different effects of pyrophosphate on prism and pyramidal sector of KDP crystals can explain this case. The method of eliminating light scatter in pyrophosphate doped KDP crystal is discussed.

Supernormal optical characteristics in doped quaternary ammonium salt KDP crystals

Abstract Potassium dihydrogen phosphate, KH 2 PO 4 (KDP) crystals with different concentrations of quaternary ammonium salt in solution were grown. In this paper, unusual transmittance ratio properties of KDP are reported. The transmittance ratio is smaller than unity at some locations. These results indicate that the plane wave effect and optical activity are highly displaced in KDP crystals, and the effect is varies in three-dimensional positions.

In-Line Bulk Concentration Measurement by Method of Conductivity in Industrial KDP Crystal Growth from Aqueous Solution

.The conductivity of KH 2 PO 4 (KDP) aqueous solutions with varying saturation temperature from 28.5°C to 41.8°C was measured in the temperature range of 30°C to 40°C. Its proposed that the conductivity of KDP solutions can be expressed by L=L 0 +b 1 T+b 2 T 2 . This relation can be interpreted by Falkenhagens (1971) conductivity model of high concentration electrolyte solution. The experimental data agrees well to the relation with an accuracy of super-saturation within ±0.03g KDP/100g water (±0.10% relative super-saturation).