Dependence of refractive indexes dispersion for LiNbO3 on impurity

The effect of the impurities of the transition metals Co, Mn, Cr, Fe, Ni, Cu on the dispersion of the refractive indexes of LiNbO₃ is studied. The dispersion curves for LiNbO₃ are compared to those for the pure crystals. The relation between the difference of the refractive indexes of the pure and doped LiNbO₃ and the ionic radius of the impurity is established.     

Faraday Effect of BSO and BTO Crystals Doped with Cr,Mn and Cu

The influence of both photochromic doping and photochromic transitions on the effect of magneto‐optical rotation (Farady effect ‐ FE) of undoped and doped with Cr, Mn and Cu Bi₁₂SiO₂0 (BSO) and Bi₁₂TiO₂0 (BTO) crystals is studied. The present results show, that Cr, Mn and Cu increase the FE. The influence of Cr, whose affect on the optical activity (OA) of BSO is most significant, here is too negligible (Verdet coefficient (V) increases only with 1‐2 % in the range 700 ‐ 590 nm). The Mn‐doping of BSO led to a V‐increase with about of 11 % in the range 400 ‐ 700 nm, as at 460 nm the relative increase of V reaches to about 30 %. The influence of Cu on FE in BSO (likely the case of the natural optical rotation) is again significant. Thus, the influence of V in the case of BSO:Cu is about 18 % in the range 700 ‐ 480 nm as reaches 28 % in the shortwave region at 480 nm. However, in BTO:Cu (0.02 mol.% Cu) the influence of Cu is opposite in respect of both effects. Now the values of V increase with 21 % at 630 nm, 22 % at 590 nm, 42 % at 520 nm, and 73 % at 480 nm in comparison to BTO‐undoped.     

O− centre formation in YAG crystals doped with iron group ions

The colour changes of YAG crystals doped with Ti, V, Cr, Mn, Fe, Co and Ni as well as those doped with Mg or Be are described. The comparison of samples annealed in hydrogen oxygen and argon and exposed to an UV irradiation is given. Yellow or brown colour of YAG crystals is attributed to the O⁻ centre formation which causes an increase of absorption, particularly near 400 nm. Most intensive coloration showed the crystals containing iron group ions in a higher valency state after UV irradiation and some crystals (e. g. YAG:Cr) annealed in argon.     

Growth and Structure of Doped KLN Crystal

KLN, Fe:KLN, Mn:KLN and Cu:KLN crystals were grown by Czochraski method. The structure of crystal was measured by X‐ray diffraction technique. The results indicated that the doped crystals kept the same structural characteristics as the pure KLN crystal, but the lattice constants of Fe:KLN and Mn:KLN crystals became smaller than that of pure KLN crystal, and that values of Cu:KLN crystal became larger than that of pure KLN crystal. This indicated that Fe and Mn cations replaced Nb cation, and Cu cation replace K cation after they entered into the lattice of KLN crystal. The result of ultraviolet‐visible absorption spectra was identified with that of X‐ray diffraction analysis.     

Mn、Cu共掺ZnO磁性的研究

本文采用水热法,分别以ZnO、Zn(OH)2为前驱物,添加一定量的MnCl4.4H2O和CuSO4.2H2O, 3mol/LKOH作矿化剂,温度430℃,填充度35%,反应24h,制备了Mn、Cu共掺ZnO晶体。当前驱物为Zn(OH)2时,所得晶体大部分为短柱状晶体,显露正负极面{0001}、{0001-}、负锥面-p{101-1-}和柱面m{1-010},长度约为30 ～50μm。少部分晶体为单锥六棱柱状,显露正锥面p{101-1},柱面m{1-010},负极面-c{0001-},晶体的长度约为100μm,长径比为5:1。当ZnO用作前驱物时,短柱状晶体长度大约为10 ～30μm,晶体的六棱对称性都出现较大的偏差。X射线荧光能谱分析表明,前驱物为ZnO、Zn(OH)2时,Mn离子含量在分别为3.19%和1.62%原子分数,没有检测到Cu离子。虽然Mn、Cu离子的掺入会明显影响晶体形态,磁性测量显示掺杂Mn、Cu的ZnO仍为反铁磁。     

Growth and characterization of TGS and DTGS single crystals doped with Pt(II), Pt(IV) and L‐alanine

The single crystals of triglycine sulfate doped with bivalent and tetravalent Pt‐ions and with L‐alanine (LADTGS/Pt(II) and LATGS/Pt(IV)) were grown in the ferroelectric phase from low temperature solutions. Using stick seeds the full‐shaped crystals with many growth pyramids have been prepared. The growth rate along the axis c of the doped crystals is much higher than in an undoped one. Morphology, domain structure and P‐E hysteresis loops have been investigated. The effect of the dopant on the growth velocity is explained on the basis of catalytic action of supposed platinum complexes. The first series of the pyroelectric detectors have been prepared from these materials and their fundamental parameters are presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of doping on OH absorption in LiNbO3 crystals

Undoped, Cr doped and Mg, Cr codoped LiNbO₃ crystals were grown by conventional Czochralski technique. Comparative study was carried out using Fourier transform infrared (FTIR) and UV‐Visible spectroscopy. Infrared optical absorption for OH^– ion has been used to study the effect of dopants on the crystals. The peak position of OH^– shift to 3535 cm^‐1 for Mg, Cr codoped crystals compared to 3484 cm^‐1 for undoped and Cr doped crystals. Prominent absorption bands are found in the visible region centered at 480 nm (20833 cm^‐1) and 653 nm (15313 cm^‐1) in Cr doped crystals. Whereas in Mg, Cr codoped crystals these broad absorption bands are red shifted to 517 nm (19342 cm^‐1) and 678 nm (14749 cm^‐1). UV cutoff in Cr doped crystals shift towards higher wavelength compared to undoped LiNbO₃ crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and electric conductivity of V2O5 single crystals

Present paper deals with the preparation of V₂O₅ single crystals, both pure and doped with Mg, Mn, and Fe respectively, by the method of zone melting. To verify the quality of crystals, measurements of electric conductivity were carried out in the direction perpendicular to cleavage plane (010). The results have shown that the prepared crystals are suitable for further investigation of physical properties.     

Flux growth of ZnO crystals doped by transition metals

ZnO crystals doped with Cr, Mn, Fe and Co were grown by the flux method. The prepared crystals revealed no phase separation detectable by X-ray diffraction. Structure properties were characterized by Raman and photoluminescence spectroscopy. For ZnO:Co, Mn and Cr, no spontaneous ferromagnetic moment was observed up to T=2 K whereas for the ZnO:Fe crystals the m(H) curves suggest the existence of 5 nm superparamagnetic iron clusters. At low temperatures the m(H) curves can be interpreted as a superposition of major paramagnetic and minor antiferromagnetic contribution. The paramagnetic part corresponds to the presence of Co²⁺, Fe³⁺, Mn²⁺ ions and small Cr atom clusters.     

Growth and characterization of pure and metal doped bis(thiourea) zinc chloride single crystals

Metal (Cd²⁺ and Cu²⁺) substituted single crystals of Bis(thiourea) zinc chloride (BTZC) are grown by slow solvent evaporation technique, with the vision to improve the physicochemical properties of the sample. Single crystal XRD studies of both pure and doped samples are carried out and the results are compared. Optical absorption and FTIR studies are performed to identify the UV cut‐off range and the presence of various functional groups in the grown crystals. The thermogravimetric (TG) analysis of metal doped BTZC indicates a marginal increase in the thermal stability of the crystals. The dielectric response of the samples have been studied in the frequency range 100 Hz to 5 MHz at room temperature and the results are discussed. Photoconductivity studies carried out on pure and metal doped BTZC crystals revealed the negative photoconducting nature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimisation of chromium doping in LiNbO3 single crystals

Growth of undoped and Cr doped (0.1, 0.25 and 0.5 mol % Cr₂O₃) congruently‐ melting‐composition LiNbO₃ single crystals by Czochralski technique is reported. Chromium doping was optimised to get crystals with potential for an integrated, broadband, tunable laser in the 700‐1100 nm spectral range. Typical sizes of the grown crystals are 25‐30 mm in diameter and 30‐40 mm in length. Symmetrical and sharp conoscopy pictures confirm the optical homogeneity of the crystals. Optical transmission was recorded for both undoped and doped crystals. 70% transmittance was observed. The grown crystals have reasonably good laser damage threshold. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nd:NaY(WO4)2激光晶体光谱性能研究

Nd:NaY(WO4)2 是一种性能优良的激光晶体.本文采用提拉法生长了Nd:NaY(WO4)2晶体,测试了该晶体的吸收光谱和光荧光光谱.结果表明,该晶体在804nm、752nm、586nm附近有较强、较宽的吸收峰,适合于LD泵浦.从光荧光光谱得到发射波长分别为1064nm和1350nm,并计算了晶体的吸收截面和发射截面.     

Micro- and nanostructures in lithium niobate single crystals doped with lanthanides

Lithium niobate single crystals doped with lanthanides (Gd, Er) and nominally pure single crystals of congruent and stoichiometric compositions have been grown under time-dependent thermal conditions. Regular growth domain microstructures and periodic nanostructures have been investigated by optical microscopy and atomic force microscopy with a step from 10 to 100 nm. Comparative investigations of the Raman spectra of lithium niobate single crystals of different compositions have been performed.     

过渡金属离子(Mn,Fe,Co)掺杂铝酸锂晶体的生长及光谱分析

采用提拉法分别生长了掺杂Mn、Fe以及Co元素的LiAlO2晶体,并对其结晶质量和光谱特性进行了研究.结果表明,LiAlO2:Mn、LiAlO2:Fe和LiAlO2:Co晶体的X射线双晶摇摆曲线半高宽分别为23.2 arcsec、12.9 arcsec和23.8 arcsec.LiAlO2:Mn与LiAlO2:Fe晶体在可见至近红外波段具有较高的透过率,而LiAlO2:Co晶体在500～700 nm波段存在吸收带;光致激发与发射光谱表明Mn2+在LiAlO2:Mn晶体中处于四面体晶体场内,而Fe3+替代Li+处于八面体格位;X射线激发发射光谱分析得出空气退火后γ-LiAlO2晶体出现了较强的缺陷发光,可归结为Li2O挥发后形成的F+心,而在同样退火条件下掺杂LiAlO2晶体中相应的缺陷发光不明显,说明Li2O的挥发被抑制,晶体的热稳定性得到了改善.     

Habit modification and improvement in properties of potassium hydrogen phthalate (KAP) crystals doped with metal ions

Potassium hydrogen phthalate (KAP) single crystals were grown by slow evaporation and slow cooling techniques. The growth procedure like temperature cooling rate, evaporation rate, solution pH, concentration of the solute, supersaturation ratio etc., has been varied to have optically transparent crystals. Efforts were made to dope the KAP crystals with rubidium, sodium and lithium ions. The dopant concentration has been varied from 0.01 to 10 mole percent. Good quality single crystals were grown with different concentrations of dopants in the mother phase. Depending on the concentration of the dopants and the solution pH value, there is modification of habit. Rubidium ions very much improve the growth on the prismatic faces. The transparency of the crystals is improved with rubidium and sodium doping. The role of the dopants on the non‐linear optical performance of KAP indicates better efficiency for doped crystals. The grown crystals were characterized with XRD, FT‐IR, chemical etching, Vickers microhardness and SHG measurements. The influence of the dopants on the optical, chemical, structural, mechanical and other properties of the KAP crystals was analysed. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

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.     

Structural and optical investigations on Mn doped Li2B4O7 crystals

Lithium tetraborate crystals have great demand due to its non‐critical phase matching at 90°. Transparent and good optical quality single crystals of undoped and Mn doped Li₂B₄O₇ were grown by Czochralski technique in air atmosphere. The crystalline phase was determined by X‐ray diffraction. Doping of Mn in the grown crystals was confirmed by energy dispersive analysis of X‐rays (EDAX) technique. Transmission spectra show that the crystal is transparent in the visible region. Birefringence interferograms were recorded to qualitatively analyse the optical homogeneity of the grown crystals and to quantify the birefringence of the samples in desired crystal direction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.     

Elastic properties of KGd(WO4)2:Ho3+ single crystals studied by Brillouin spectroscopy

The analysis some of the acoustic phonons propagating in pure and Ho³⁺‐doped KGd(WO₄)₂ single crystals in the GHz frequency range by Brillouin scattering method has been presented. For investigated crystals the velocities of the longitudinal and transverse acoustic phonons [100], [010], [001], [101], [101] and [110] have been determined. Moreover, the value of elastic constants C₂₂, C₄₄ and C₆₆ of pure and Ho³⁺‐doped KGd(WO₄)₂ single crystals have been estimated. It was revealed that the presence of the Ho³⁺‐ions in KGd(WO₄)₂ crystals, for the used doping concentration 1 at% and 8 at%, does not influence their elastic properties. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and Characterisation of Gel-grown Lead(II)Chloride and Lead(II)Bromide Single Crystals

Single crystals of pure and doped lead(II)chloride and lead(II)bromide were grown by gel technique employing a modified two-stage chemical reaction. Methods to minimise the predomination of needle morphology during the growth of these crystals have been investigated and the results are discussed. The grown crystals were characterised by optical transmission spectrum. Undoped and monovalent cation (K⁺, Na⁺, Cu⁺, Ag⁺ and Hg⁺) doped crystals of PbCl₂ and PbBr₂ were subjected to d.c. electrical conductivity studies. Using the log σT versus T⁻¹ plot, the activation energies for the migration of anion vacancies in lead(II)halides are calculated. They are found to be less for the doped crystals than those of undoped ones.