Growth and Characterisation of Potassium Pentaborate Single Crystals

Single crystals of potassium pentaborate were grown by the solution growth method. The grown crystals were characterised by optical transmission spectrum, differential thermal analysis, and thermogravimetric analysis. The coefficient of thermal expansion was also determined and the results discussed.     

Solution Growth and Characterisation of L‐alanine Single Crystals

Single crystals of L‐alanine have been grown from buffered aqueous solutions and characterised as to their optical quality via wavefront distortion analysis, electrooptical response and harmonic generation efficiency. Refraction indices as well as phase matching loci were found in satisfactory agreement with previously published data for crystals grown in non buffered solution. Estimates for the electro‐optical response are reported for the first time. The experimentally observed crystal habit is discussed in terms of morphological importance (M.I.), which was found to be in disagreement with the predictions of crystallographic criteria based on the interplanar distance d_hkl, on the periodic bond chains (PBC) and the attachment energy E_att. This disagreement is tentatively attributed to the presence of impurities and non‐appropriate supersaturation conditions.     

铌锌酸铅-钛酸铅单晶的生长及性能

本文系统地研究了(1-x)Pb(Zn1/3 Nb2/3)O3-xPbTiO3(PZN-PT)单晶的光学透过率与结晶取向和组分的关系,发现四方相单晶的透过率明显大于三方相和准同型相界(MPB).[001]方向极化的四方相PZN-12％PT单晶在0.5～5.8μm的波段范围内,未镀增透膜的晶片透过率约为65％;准同型相界处...     

Growth of Triglycine Sulphate Single Crystals Doped by Cobalt (II) Phosphate

Modified TGS single crystals have been grown by doping with Cobalt (II) Phosphate in ferroelectric phase. The effects of different amounts of doping entities on the growth habit and P‐E hysteresis loop have been investigated. The experimental results show that while the spontaneous polarization P_s measured on variously doped crystals remains virtually unchanged, the coercive field values differ in dependence on the growth conditions and grown pyramidal features. The highest values of the coercive field E_c have been found to fall in the interval 800‐900 V/cm.     

Growth and Characterisation of Pure and Nickel-doped Strontium Tartrate Tetrahydrate Single Crystals

Strontium tartrate tetrahydrate single crystals doped with nickel have been grown in silica gel. The grown crystals have been characterized by X-ray, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and etching technique.     

Growth and Characterisation of (CuInTe2)1‐x(2 ZnTe)x Solid Solution Single Crystals

The crystal structure as well as the optical properties in the band gap region of (CuInTe₂)_1‐x(2 ZnTe)_x solid solution single crystals grown by directional freezing have been studied. The lattice constants exhibit a linear dependence on crystal composition. The chalcopyrite‐sphalerite phase transition was observed between x = 0.3 and x = 0.4°. The variation of the band gap with respect to crystal composition can be described by a quadratic expression.     

Vapour-liquid-solid Growth and Characterisation of N-methylurea Crystals

A new growth method, based on a vapour-liquid-solid (VLS) mechanism, is reported for preparing single crystals of N-methylurea (NMU), a material which appears to be a good alternative to urea for non-linear optical applications in the “near UV-visible” region of the spectrum. Details of the growth procedure are given and it is shown that large single crystals, with volumes up to 7 ÷ 10 cm³, can be obtained with satisfactory reproducibility and very fast growth rate. Structural and optical characterisation, still preliminary, are reported, which evidence a crystalline quality comparable to that of urea and N-methylurea as previously grown with other growth techniques. Cryst. Res. Technol., Vol. 32, No. 1.     

Growth and Characterization of Urea-(DL) Tartaric Acid Single Crystals

A new organic UV nonlinear optical crystal urea-(DL)tartaric acid [CO(NH₂)₂₋(DL) C₄H₆O₆] (abbreviated as U(DL)T) is reported. Large single crystals have been grown from aqueous solution by the cooling method. They belong to the monoclinic space group P2₁ and the lattice parameters are: a = 7.6973 Å, b = 23.3310 Å, c = 4.8727 Å, and β = 100.82°. The structure and some of its physical properties have been determined. The crystal is transparent from 0.24 to 1.95 μm. The efficiency of powder SHG is larger by one order of magnitude than that of KDP. Thus the crystal will be a useful NLO material.     

Influence of Host Lattice in Interstital Dopant Sites: EPR Studies on Cu (II) Doped Sarcosine Cadmium Bromide Single Crystals

EPR study of Cu(II) doped in sarcosine cadmium bromide single crystals are carried out at room temperature. The impurity ions occupy the interstitial position in this crystal lattice. Crystalline field around the Cu(II) ion in this low symmetry crystal is rhombic. The transitions arise from a single paramagnetic site with g_xx = 2.1082, g_yy = 2.0005, g_zz = 2.2071, and A_xx = ‐64 x 10^‐4 cm^‐1, A_yy = ‐23 x 10^‐4 cm^‐1, A_zz =‐185 x 10^‐4 cm^‐1. The ground state is an admixture of dx2‐y2 and dz2 states. The observed molecular orbital coefficient value a2 = 0.85 reveals a moderate covalency of the s bonding and b2 = 0.967 indicates the weak pi bonding. A strong interaction between Cu(II) and nitrogen ligands is found to exist.     

氙离子注入氯化钾和溴化钾晶体光谱特性

用36keV氙离子注入,有效地使氯化钾和溴化钾晶体着色.在室温下,对着色晶体进行系统光谱分析.在着色晶体中,观测到大量F、R、M和未知色心,并给出色心生成与转化机理.用解谱的方法,分别从着色氯化钾和溴化钾晶体吸收光谱中合理地分解出K、F、R、M和一些其它吸收带,并精确确定这些吸收带的光谱参数.     

Supersaturation by gelling: Gel-grown single crystals of metal(II)carboxylates

Hydrolysis and polycondensation of tetraalcoxysilanes create both: a crystal growth medium and an alcohol-water mixture with diminished solubility for a lot of compounds. Solvent varying gel crystallization is shown for twenty metal(II)carboxylates in TMOS. The influence of pH-value, salt- and TMOS concentration and combination of this method with cooling crystallization are described.     

CdSe单晶体的生长及其特性研究

本文报道了用改进的垂直气相法(多级提纯垂直气相法)生长富Cd的CdSe单晶体,并对晶体的性能进行了观测,其电阻率为107Ωcm量级,电子陷阱浓度为108cm-3量级,第一次报道了(110)面的腐蚀形貌。结果表明：采用这种方法制备CdSe单晶,设备简单,易于操作,在提纯和生长过程中不需要转移原料,有利于减少晶体中的杂质含量,降低位错密度,改善晶体的电学性能。多级提纯垂直气相法是一种有前途的CdSe单晶体生长的新方法。     

Growth of Vanadyl Pyrophosphate Single Crystals

The present work communicates about the first successful attempt at growing of sizeable single crystals of vanadyl pyrophosphate (VO)₂P₂O₇ (VOPO) — a low dimensional antiferromagnet. The growth of VOPO is complicated by two features of this compound. The first is a strong sensitivity of the oxydation state of vanadium (and stability of VOPO) to the oxygen content in the growth atmosphere. The second is a tendency of the VOPO-melt to glass formation during the cooling due to its high viscosity. Therefore the growth has to be carried out with a very low growth rate and in an atmosphere with exactly controllable oxygen content. The best results were achieved with a combination of Czochralski and Kyropoulos techniques, i.e. pulling of crystals with simultaneous cooling of the melt. Crystals of VOPO with sizes up to 10 × 5 × 3 mm³ have been grown. The growth from the melt is accompanied by growth from gaseous phase also (sublimation). Since the VOPO phase has a homogeneity range in oxygen content, attention was paid to the composition of the grown crystals. Growth experiments combined with TGA and XRD measurements show, that the oxygen content and thus the oxidation state of vanadium in the crystals can be adjusted accurately.     

Preferred Growth of Antimony Single Crystals

Single Crystals of antimony were grown by the Chalmer's method from the melt. The crystals were grown under different temperature gradients of 92 °C/cm, 75 °C/cm and 52 °C per cm. The growth velocities were varied from 1.5 cm/hr to 9 cm/hr. At low growth velocities antimony exhibits a preferred orientation in the range 1 cm/hr to 6 cm/hr. No effect of temperature gradient is observed. The results are compared with those of bismuth, cadmium and zinc which are contradictory to what has been observed.     

碘化铅(PbI2)单晶体的生长研究

本文以高纯Pb、I2单质为原料,在特殊设计的密闭石英安瓿中,采用两温区气相输运方法成功合成出PbI2多晶原料,避免了安瓿的爆炸.以此为原料,用垂直Bridgman法生长出尺寸为φ15mm×30mm的PbI2单晶锭.该晶锭外观完整、呈橙黄色、半透明状,其电阻率为1010Ω·cm量级,X射线衍射分析获得了(001)面的四级衍射谱,表明该晶体是结构完整的单晶体,可用于探测器的制作.