When the crystal grows from solution,a sharp variated fluid layer of the solute concentration exists against crystal surface.The sharp variated fluid layer is defined the boundary layer in crystal growth.The molecular...When the crystal grows from solution,a sharp variated fluid layer of the solute concentration exists against crystal surface.The sharp variated fluid layer is defined the boundary layer in crystal growth.The molecular structure of the boundary layers plays a key role in crystal composition,morphology,growth rate and crystal growth mechanism.However,owing to the lacking of suitable probe technique,it is difficult to obtain the information of the moving construction of the boundary layers.Here,the laser Raman Microprobe combining with holographic phase contrast interferometric microphotography is used to probe in situ the molecular structure of the boundary layers during the crystal growth processes of KH 2PO 4(KDP) and KD 2PO 4(DKDP).In supersaturations ranging from 1% to 14%,Raman scattering states at the different positions within the boundary layers have been investigated,and compared with the bands of different concentration solutions alone using laser Raman spectroscopy between 600 and 1350cm -1 .The changes in band parameters of the phosphates within the boundary layers of crystal growth are different from those in solution alone.The influence of the solution concentration on the band parameters of anion phosphate within the layers is nonlinear.With increasing supersaturation,the full width at half height of the P=O 2 symmetric stretch band increases.The new 918(938)cm -1 H(D)O P OH(D) asymmetric stretch,1120(DKDP 1200)cm -1 O P O asymmetric stretch,and extremely weak 1210cm -1 P O H in plane deformation bands appear in the characteristic boundary layers.These new bands show that the cations have direct effects on the phosphate group(aggregates).Under the driving of concentration gradient field of supersaturation,the effects of cations cause the changes of O P O bond angle,atomic charge redistribution,and lead to readjust geometry of anion phosphate group and desolvation.The trend of readjust is close to the geometry of the crystal structure unit and the formation of the cations phosphate crystallization unit.展开更多
Large size and high quality single crystals GdCa_(4)O(BO_(3))_(3) have been grown from platinum crucible under air atmosphere by the conventional rf-heating Czochralski method.The crystal growth conditions,growth habi...Large size and high quality single crystals GdCa_(4)O(BO_(3))_(3) have been grown from platinum crucible under air atmosphere by the conventional rf-heating Czochralski method.The crystal growth conditions,growth habits,and transmission spectra were investigated.The crystal is transparent in the visible and near-infrared region(320-2600nm).It has a good second harmonic generation phase-matching condition.The phase-matching experiment result is well consistent with the theoretical one.The frequency-doubling efficiency is 26.7% in the phase-matching angles θ=45o and ø=45.1o direction.展开更多
From the view of crystal chemistry, the growth units and forming mechanism of KDP crystals were investigated. The thickness of boundary layers changing with lattice faces was studied by \%in\|situ\% observation with R...From the view of crystal chemistry, the growth units and forming mechanism of KDP crystals were investigated. The thickness of boundary layers changing with lattice faces was studied by \%in\|situ\% observation with Raman spectra, where the solution structure during crystal growth could be well observed. It was found that the solution structure at the boundary layer is similar to that of the crystal, so that the growth units are proposed as \[H\-2PO\-4\]\+-. The difference of growth rates of lattice faces is determined by the combination of growth units, which is mainly dominated by the angular orientation of K\|O and H\|O bonds. Consequently the reason about the difference of growth rates of lattice faces and the influence of pH value on the crystal morphology can be well elucidated.展开更多
文摘When the crystal grows from solution,a sharp variated fluid layer of the solute concentration exists against crystal surface.The sharp variated fluid layer is defined the boundary layer in crystal growth.The molecular structure of the boundary layers plays a key role in crystal composition,morphology,growth rate and crystal growth mechanism.However,owing to the lacking of suitable probe technique,it is difficult to obtain the information of the moving construction of the boundary layers.Here,the laser Raman Microprobe combining with holographic phase contrast interferometric microphotography is used to probe in situ the molecular structure of the boundary layers during the crystal growth processes of KH 2PO 4(KDP) and KD 2PO 4(DKDP).In supersaturations ranging from 1% to 14%,Raman scattering states at the different positions within the boundary layers have been investigated,and compared with the bands of different concentration solutions alone using laser Raman spectroscopy between 600 and 1350cm -1 .The changes in band parameters of the phosphates within the boundary layers of crystal growth are different from those in solution alone.The influence of the solution concentration on the band parameters of anion phosphate within the layers is nonlinear.With increasing supersaturation,the full width at half height of the P=O 2 symmetric stretch band increases.The new 918(938)cm -1 H(D)O P OH(D) asymmetric stretch,1120(DKDP 1200)cm -1 O P O asymmetric stretch,and extremely weak 1210cm -1 P O H in plane deformation bands appear in the characteristic boundary layers.These new bands show that the cations have direct effects on the phosphate group(aggregates).Under the driving of concentration gradient field of supersaturation,the effects of cations cause the changes of O P O bond angle,atomic charge redistribution,and lead to readjust geometry of anion phosphate group and desolvation.The trend of readjust is close to the geometry of the crystal structure unit and the formation of the cations phosphate crystallization unit.
文摘Large size and high quality single crystals GdCa_(4)O(BO_(3))_(3) have been grown from platinum crucible under air atmosphere by the conventional rf-heating Czochralski method.The crystal growth conditions,growth habits,and transmission spectra were investigated.The crystal is transparent in the visible and near-infrared region(320-2600nm).It has a good second harmonic generation phase-matching condition.The phase-matching experiment result is well consistent with the theoretical one.The frequency-doubling efficiency is 26.7% in the phase-matching angles θ=45o and ø=45.1o direction.
文摘From the view of crystal chemistry, the growth units and forming mechanism of KDP crystals were investigated. The thickness of boundary layers changing with lattice faces was studied by \%in\|situ\% observation with Raman spectra, where the solution structure during crystal growth could be well observed. It was found that the solution structure at the boundary layer is similar to that of the crystal, so that the growth units are proposed as \[H\-2PO\-4\]\+-. The difference of growth rates of lattice faces is determined by the combination of growth units, which is mainly dominated by the angular orientation of K\|O and H\|O bonds. Consequently the reason about the difference of growth rates of lattice faces and the influence of pH value on the crystal morphology can be well elucidated.
