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1.
采用润湿导模技术生长出大块的片状铌酸锂单晶,尺寸可达200mm长、20mm宽、3mm厚。经测试,性能与柱状单晶相同。为了做好此项工作,我们测定了铌酸锂熔体的密度ρm与表面张力α等物理常数,得出在1270℃时ρm=3.57×103kg/m3,α=204dyne/cm;在1300℃时ρm=3.42×103kg/m3,α=192dyne/cm。 关键词:  相似文献   

2.
We have investigated the photorefractive (photoinduced) light scattering in lithium niobate single crystals: LiNbO3, LiNbO3:B, LiNbO3:Y(0.46 mas %), LiNbO3:Y(0.24):Mg(0.63 mas %), and LiNbO3:Ta(1.13):Mg(0.0109 mas %) that were grown from congruent melts. We have found that the shape of the speckle structure of this scattering and the kinetics of the development of its indicatrix depend substantially on the type of the impurity dopant in the lithium niobate crystal. We have observed that, upon laser irradiation of crystals doped with Y3+, Ta5+:Mg2+, and Y3+:Mg2+, the shape of their scattering indicatrix changes with time. At the same time, the LiNbO3:B crystal is characterized by a complete absence of time changes in its speckle structure, which indicates that the photorefractive effect in this crystal is substantially lowered.  相似文献   

3.
A new iron center in stoichiometric lithium niobate crystals has been studied by the EPR method. The angular dependences of the EPR spectrum of the center have been used to derive the parameters of its spin Hamiltonian. The data amassed on the variation in the concentrations of two iron centers in lithium niobate crystals annealed in a Li2CO3 powder have provided an insight into the mechanism of formation of the new center, as well as corroborated its model proposed by us earlier. According to this model, the center represents a complex of two defects aligned with the polar axis in the crystal: the iron ion at the niobium site and an interstitial lithium ion filling the nearest structural vacancy (Fe3+[Nb]-Li+[V]). The structure of other Fe3+ centers revealed earlier in LiNbO3 crystals, in which the iron ion occupies the niobium site, has been discussed.  相似文献   

4.
朱镛  张道范 《物理学报》1979,28(2):234-239
文本研究了用提拉法生长的铌酸锶钠锂(Sr4NaLiNb10O30)晶体的电光、热电、介电和压电性能。其半波电压与温度的关系与晶体中锂含量密切相关。测得其室温下的热电系数与Ba~0.5的Sr1-xBaxNb2O6晶体相当,~7×10-8C/cm2·K。已极化的晶体几乎检测不到退极化现象。将其作成热电器件,其探测度D*不小于1.7×107Hz1/2·cm/W。文中还描述了其介电和某些压电性能。 关键词:  相似文献   

5.
A technique has been developed for dopant concentration depth profiling using static Secondary Ion Mass Spectrometry (SIMS), and an ex-situ ion milling facility to produce “tapers” through the region of interest of an optical waveguide sample. Results have been obtained for titanium-diffused optical waveguides in lithium niobate and for potassium and caesium ion-exchanged glass waveguides. The SIMS profiles have been compared with refractive index profiles in multimode structures. The refractive index profiles have been obtained from the waveguide mode spectra by a piecewise linear Wentzel-Kramers-Brillouin (WKB) method. The two profiles are in close agreement. Use of the SIMS technique for single mode Ti∶LiNbO3 waveguides has revealed significant changes in the forms of the profiles, compared with deeper structures, and we suggest a mechanism to account for these changes.  相似文献   

6.
The dielectric response of lithium niobate single crystal in ac fields with amplitudes E of 3.74 to 13.1 kV cm?1 is investigated at frequencies of 1 and 10 Hz in the temperature range of 70 to 200°C. The increase in effective dielectric permittivity ?eff′ and the effective dielectric losses ?eff″ is found to be associated with the formation of short-radius Nb Li 4+ polarons at temperatures T > 130°C and their contribution to polarization relaxation in a LiNbO3 crystal.  相似文献   

7.
Hyperbranched star polymer HBPS-(PPEGMA) x was synthesized by atom transfer radical polymerization (ATRP) using hyperbranched polystyrene (HBPS) as macroinitiator and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as monomer. The structure of the prepared hyperbranched star polymer was characterized by 1H NMR, ATR-FTIR, and GPC. Polymer electrolytes based on HBPS-(PPEGMA) x , lithium salt, and/or nano-TiO2 were prepared. The influences of lithium salt concentration and type, nano-TiO2 content, and size on ionic conductivity of the obtained polymer electrolytes were investigated. The results showed that the low crystallinity of the prepared polymer electrolyte was caused by the interaction between lithium salt and polymer. The addition of TiO2 into HBPS-(PPEGMA) x /LiTFSI improved the ionic conductivity at low temperature. The prepared composite polymer electrolyte showed the highest ionic conductivity of 9?×?10?5 S cm?1 at 30 °C when the content of TiO2 was 15 wt% and the size of TiO2 was 20 nm.  相似文献   

8.
A technique for measuring the spatial distribution of X-rays generated by a pyroelectric source is developed and tested. Anisotropy in the spatial distribution of X-rays from the surface perpendicular to the pyroelectric axis of the lithium niobate crystal depending on the piezoelectric crystal axis orientation was detected. The result obtained shows the necessity of considering the effect of piezoelectric properties of pyroelectric crystals on X-ray generation processes.  相似文献   

9.
The study on the optical properties of alkali borate glasses doped with rare earths is an interesting area of research. Dysporosium doped lithium magnesium borate glasses were prepared by melt-quenching technique with dysporosium concentration varying from 0.3 to 1.0 mol %. Physical and optical properties of Lithium Magnesium Borate doped with different concentration of Dy3+ were observed based on its physical parameters, emission spectra and absorption spectra. The absorption spectra of this study exhibits eight absorption bands with hypersensitive peak at 1260 nm (6 H 9/2). Two emitted spectra transitions were also observed at 4 F 9/26 H 15/2, 4 F 9/26 H 13/2. Lastly, important physical parameters for each concentration of dopant such as density, ions concentration, polaron radius, inter-nuclear distance, refractive index, oscillator strength and other parameters were determined.  相似文献   

10.
阙文修  姚熹 《物理学报》1996,45(5):811-816
利用常规X射线衍射和掠入射X射线衍射对在空气中进行镁离子内扩散的扩镁铌酸锂单晶表层的富氧化镁层特性进行了研究,揭示出镁离子内扩散初期随着体内锂离子的外扩散,首先在富氧化镁层形成Li3Mg2NbO6和Mg4Nb2O9的化合物结构,Li3Mg2NbO6出现在富氧化镁的内表层,而Mg4Nb关键词:  相似文献   

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