Influence of Quenching on Microhardness and Dislocation Mobility of Doped NaCl Crystals

The effect of quenching on microhardness and dislocation mobility of NaCl:Ca and NaCl:Pb single crystals was studied. Both the decrease and increase of these parameters in quenching occurred depending on the type and concentration of impurity and quenching temperature. The absence of correlation between the changes of microhardness and those of dislocation ensemble mobility which resulted from the quenching, has been found first. The conditions of the observation of this phenomenon were revealed and the interpretation of the experimental facts was proposed.     

光子晶体中掺杂激活杂质的光增益研究

本文借助光子晶体中二能级原子的自发辐射理论说明缺陷态局域场存在的必然性以及局域场基本性质,为研究掺杂自发辐射的内在规律提供了理论依据,在此基础上,将自发辐射理论与数值模拟相结合,在缺陷介质中掺入和未掺入激活杂质时,数值模拟研究一维光子晶体的掺杂局域场特征以及受激辐射增强和透射率大于1现象与光子带隙边缘群速度异常和掺杂层复有效折射率负的虚部之间的内在规律,由此说明如在光子晶体的缺陷介质中掺入激活杂质,复有效折射率具有负的虚部,光子禁带中会出现品质因子非常高的杂质态,具有很大的态密度,这样便可实现自发辐射的增强,出现较强的受激辐射放大,在带隙的边缘处,光子晶体的群速度较小或群速度异常,受激辐射放大最容易出现在靠近光子带隙的边缘。     

Spectral Studies on VO2+ doped MPPH Crystals

Magnesium Potassium Phosphate Hexahydrate (MPPH), is analogous to the bio‐mineral struvite. Vanadyl doped MPPH crystals are grown by slow evaporation technique. EPR and optical absorption studies are carried out at room and liquid nitrogen temperatures. Spin‐Hamiltonian, crystal field and bonding parameters are evaluated.     

Vicker's Microhardness Studies of L-arginine Hydrobromide Monohydrate Crystals (LAHBr)

Vicker's microhardness study of (100), (010) and (001) faces of a non-linear optical crystal, L-arginine hydrobromide monohydrate (LAHBr)have been reported.(100) plane is found to be the weakest plane. It has been observed that the microhardness decreases with increasing load for the three crystal planes. The microhardness behaviour have been explained successfully with the help of the PSR model proposed by Li and Bradt. Work hardening index n for the three planes are found to be greater than 1.6 which indicates that LAHBr is a soft crystal.     

Glow Curves of Thermally Pretreated KCl:Mn2+ Crystals

Thermoluminescence studies of KCl crystals doped with 0.5 mole% of Manganese both in “as grown” state and after quenching them from various elevated temperatures indicate that the position of the glow peaks is found to depend upon the state of dispersion of impurity. In quenched crystals two additional peaks one around 130 and other around 215°C are observed. Dipoles near dislocations are suggested to be responsible for 130°C peak and 215°C peak to a complex formed by the associated of one or more Mn²⁺ ions with a single vacancy or an aggregate of vacancies, the complex being situation in the dislocation region.     

Thermoluminescence and optical absorption studies of KBr crystals doped with ca2+

Thermoluminescence studies of KBr crystals doped with 0.5 mole % of Ca²⁺ both in the ‘as-grown’ state and after quenching them from various elevated temperatures indicate that the position of the glow peak which has been assigned to F-centers is found to depend upon the state of dispersion of impurity. Bleaching of the X-irradiated samples result in an additional peak and this has been attributed to Z₁-centers. Optical absorption measurements also confirm the formation of Z₁-centers in Ca²⁺ doped KBr crystals.     

Effect of Impurity Concentration and Plastic Deformation on Dislocation Density of KCl Crystals

Using the etch pit technique both the distribution and density of dislocations in undeformed and dynamically deformed nominally pure and Sr²⁺ or Pb²⁺ doped KCl crystals are examined. Additionally, the role of specimen geometry in the plastic deformation within the I deformation stage is determined. For all the crystals examined the relationship between screw dislocation density and plastic flow stress obeys the formula τ ⋍ ϱ_sc.^1/2.     

Comparison of Ba(B1-xAlx)2O4 Single Crystals on their Diameters

Small diameter crystals of Ba(B_1-xAl_x)₂O₄ were grown by Floating zone pulling down method and Micro-pulling down method to be compared with large diameter crystals grown by Czochralski method. While the Czochralski grown crystal was opaque, the crystal transparency was actually improved with the decrease of crystal diameter, i.e., the decrease of constitutional supercooling. The reason was the increase of temperature gradient caused by down-sizing of the crystal diameter deduced by down-sizing of the growth furnace. The adequate diameter for transparent crystal was determined depending on the Al content.     

The Role of Impurity Precipitation on Ionic Conductivity of NaCl:Sr System

Ionic conductivity studies of NaCl crystals doped with 1 mole% of strontium both in as grown state and after quenching them from 550°C indicate that the conductivity depends on the impuritiy precipitates. It is found that all conductivity plots of pure NaCl, NaCl:Sr and NaCl:Sr crystals quenched from 550°C are straights lines, both in extensive and intrensic regions. The conductivity of NaCl: Sr system is always less than that of pure NaCl crystal. The results are explained on the basis of state of dispersion of impurities.     

铁杂质对LiNbO3晶体折射率的影响

测定了纯LiNbO3晶体和两种掺铁的LiNbO3晶体的折射率和晶格常数,并对三种样品的折射率和晶格常数进行了比较,发现了掺铁后的LiNbO3晶体折射率及晶格常数都有微小的变化,讨论和分析了引起这些变化的原因。     

Ca^2＋对KDP晶体的光损伤阈值的影响

Ca2 是KDP原料中一种常见的杂质离子,这种杂质不仅会影响晶体的生长过程,而且会加重晶体的光散射.通过传统降温法和点籽晶快速生长法生长不同Ca2 掺杂浓度的KDP晶体样品,对样品进行激光损伤实验,结果表明,Ca2 的存在降低了KDP晶体的光损伤阈值,其原因主要在于Ca2 掺杂导致晶体内部缺陷增多,内应力增加以及晶体中的散射颗粒密度增大使晶体光吸收加重.     

Density,Colourability and Conductivity of Sr2+ Doped KCl Crystals

The measurements of colourability and density changes in KCl crystals with different Sr²⁺ contents point to the presence of two separate doping ranges in which different mechanisms of Sr²⁺ incorporation are active. Below 350 ppm Sr/KCl substitutional incorporation and above 350 ppm Sr/KCl precipitation of a second phase predominates. The latter process is accompanied by the formation of larger vacancy clusters. Ionic conductivity measurements imply that in the range between 80 and 350 ppm the aggregation of Sr²⁺ [+] dipols takes place.