共查询到20条相似文献,搜索用时 62 毫秒
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研究了BGO晶体在不同温度下(在300—1323 K的温度范围)的拉曼光谱及其熔体的高温拉曼光谱,分析了BGO晶体结构随温度变化的规律及BGO熔体的结构特征.随着温度的升高,BGO晶体的拉曼光谱谱峰都不同程度地向低波数方向移动,也存在不同程度的展宽,同时强度减弱.另外,在BGO熔体中存在[GeO4]和[BiO6]的结构基团;但两种结构之间的联键消失,即在熔体中二者是相互独立的生长基元.
关键词:
高温拉曼光谱
熔体
BGO晶体 相似文献
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测量并研究了不同温度(室温—1573 K)范围内KTN晶体的拉曼光谱及其熔体的高温拉曼光谱,分析了KTN晶体结构随温度变化的规律及其熔体的结构特征.随着温度的升高,KTN晶体的拉曼光谱谱峰都不同程度地向低波数方向移动,同时存在不同程度的展宽,并伴随强度的减弱.观察并解释了温度353 K附近KTN晶体样品的四方—立方转相现象.研究了KTN晶体拉曼光谱中538cm-1,585cm-1,835cm-1和877cm-1谱峰及其
关键词:
高温拉曼光谱
熔体
KTN晶体 相似文献
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BSO晶体生长固/液边界层结构的实时观测研究 总被引:3,自引:0,他引:3
实时测量BSO晶体水平区熔法生长过程中,研究固/液边界层以及边界层两侧的晶体和熔体的显微拉曼光谱,晶体生长固/液边界层以及边界层两侧的熔体和晶体的结构特征, 生长基元结构从熔体结构经边界层过渡到晶体结构的变化过程。结果显示, BSO熔体中存在Bi3O4和[SiO4]的键合结构; Bi3O4分子基团在固/液边界层聚合形成[BiO7]八面体单体、多聚体,与[SiO4]结构基团联结,在通过固/液边界层时进入格位。 相似文献
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用高温晶体生长实时观察装置,发现了KABO晶体生长形态随着生长体系过饱和度的增大从六方形态逐渐向三角形态过渡,然后又从三角形态逐渐向六方枝蔓晶形态过渡的过程.通过KABO生长溶液高温拉曼谱的测试结果,证明了溶液中存在[BO3]3-三角形、[AlO4]5-四面体生长基元.运用负离子配位多面体生长基元理论模型,分析了KABO晶体上述生长形态演化的机理.发现KABO的生长形态是由其内部结构和生长基元共同决定的,在不同过饱和度溶液中,KABO生长基元的种类和维度将会发生变化,由此相应引起了KABO的生长形态从六方形态到三角形态,又从三角形态向六方枝蔓晶形态的演变过程.
关键词:
KABO晶体
负离子配位多面体
生长形态
枝蔓晶 相似文献
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采用高温原位拉曼光谱技术,研究了Li2B4O7从常温至1 373 K温度范围内的拉曼光谱。在升温过程中,晶体的拉曼光谱出现展宽和红移现象,且强度降低。晶体熔化时,由2个[BO4]和2个[BO3]组成的[B4O9]环状结构转变成(B3O6)3- 六元环和[BO3]结构,[BO4]结构减少直至消失。基于密度泛函理论,计算了Li2B4O7晶体的拉曼光谱,对其振动模式进行了分析归属。利用量子化学从头计算法计算了由[B3O6-BO3]为基础相互连接形成的x(Li2B4O7)(x=2, 3, …, 9)的环状团簇模型的拉曼光谱,对Li2B4O7熔体的结构进行了模拟分析。计算结果表明Li2B4O7熔体的阴离子基元为三个(B3O6-BO3)组成的大三元环超级结构。 相似文献
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The kinetics of a monolayer growth is studied using the two-dimensional lattice gas model by means of the path-probability method (PPM) for nonequilibrium phenomena. Kinetic equations for the combined processes of relaxation (adsorption and desorption) and diffusion are derived analytically and solved for the first time in the square approximation of the PPM. Comparison of the square approximation with the point and pair approximations along with Monte Carlo simulation shows the effect of using a larger basic cluster than in the previous studies. When the square approximation is used, the growth rate results are much improved in both cases with and without diffusion and agree well with the Monte Carlo simulations results, except for very small values of the driving forceL=/k
b
T where is the chemical potential difference between the vapor and the solid phase. In the range where the agreement is good, there exists a region where the growth rateR is proportional to exp(–c/L with a constantc. This is the feature which is characteristic of two-dimensional nucleation-limited growth. 相似文献
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Self-assembled InAs quantum dots (QDs) with high-density were grown on GaAs(0 0 1) substrates by antimony (Sb)-mediated molecular beam epitaxy technique using GaAsSb/GaAs buffer layer and InAsSb wetting layer (WL). In this Sb-mediated growth, many two-dimensional (2D) small islands were formed on those WL surfaces. These 2D islands provide high step density and suppress surface migration. As the results, high-density InAs QDs were achieved, and photoluminescence (PL) intensity increased. Furthermore, by introducing GaAsSb capping layer (CL), higher PL intensity at room temperature was obtained as compared with that InGaAs CL. 相似文献
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Barabási AL 《Physical review letters》1993,70(26):4102-4105
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A new method of the moving-boundary problem analysis is developed. After proposed coordinate transformation, the quasi-steady-state differential equation was reduced to equivalent Laplace equation. Transformed boundary conditions of a rescaled field distribution reflect the presence of rate-dependent sources on interface. Taking into account the local rate-dependence of the Neumann's boundary conditions, non-equilibrium pattern formation was considered. The problem of dendrite fractal growth was reduced to one of interaction of conformal to tips charged particles. Conditions of the quasi-steady growth and the recurrence formula for k-order dendrite spacing were derived. Theoretically obtained scaling laws for interface shape, dendrite spacing, critical sidebranch distance are confirmed by available experimental data. 相似文献
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We consider the role of fluid shear in maintaining anomalous “hotspot” solutions reported for a chaotically stirred bistable chemical reaction model [S.M. Cox, Persistent localized states for a chaotically mixed bistable reaction, Phys. Rev. E 74 (2006) 056206]. In the well-mixed regime, the chemical concentration is governed by a single autonomous ordinary differential equation with two stable equilibria. Whether the reaction goes to extinction or to an excited state depends on whether the initial concentration lies below or above some unstable threshold. By contrast, when the concentration varies spatially, and the chemical is stirred, the interplay between advection, diffusion and reaction is much more complicated, and the fate of the reaction depends sensitively on the initial conditions. It has previously been shown that, if the stirring is temporally periodic, a localised hotspot may form, and so the system never becomes fully extinct, nor fully excited. In this work, we first demonstrate that hotspots are in some sense generic, in that they are easily found by trial and error, by choosing reaction parameter values between those giving rise to global extinct and excited states. We also show that hotspots may be associated with hyperbolic, elliptic or even parabolic orbits associated with the underlying stirring. We observe that fluid shear is an important mechanism in localising a hotspot, and derive a reduced ordinary differential equation model which can predict the fate of a chemical stripe in a shear flow accurately. 相似文献