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221.
N. Dhahri J. DhahriE.K. Hlil E. Dhahri 《Journal of magnetism and magnetic materials》2012,324(5):806-811
The critical properties of perovskite manganite La0.67Pb0.33Mn1−xCoxO3 (0≤x≤0.08) around the paramagnetic-ferromagnetic phase transition are investigated through various techniques such as the modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis. Though the nature of this transition was found to be in second order, the estimated critical exponents β (0.233≤β≤0.368), γ (1.03≤γ≤1.40) and δ (4.32≤δ≤5.54) are in between the theoretically predicted values for three-dimensional Heisenberg and tricritical mean-field model. This model suggests the coexistence of the short-range and long-range ferromagnetic orders around the critical temperature. The values of the critical exponents obtained from different methods and the well-obeyed scaling behavior confirm that the calculated exponents are unambiguous and purely intrinsic to the system. 相似文献
222.
M.A. AliA.K.M.A. Islam 《Physica B: Condensed Matter》2012,407(6):1020-1026
The structural, elastic, electronic and optical (x=0) properties of doped Sn1−xBixO2 and Sn1−xTaxO2 (0≤x≤0.75) are studied using the first-principles pseudopotential plane-wave method within the local density approximation. The independent elastic constants Cij and other elastic parameters of these compounds have been calculated for the first time. The mechanical stability of the compounds with different doping concentrations has also been studied. The electronic band structure and density of states are calculated and the effect of doping on these properties is also analyzed. It is seen that the band gap of the undoped compound narrowed with dopant concentration, which disappeared for x=0.26 for Bi doping and 0.36 for Ta doping. The materials thus become conductive oxides through the change in the electronic properties of the compound for x≤0.75, which may be useful for potential application. The calculated optical properties, e.g. dielectric function, refractive index, absorption spectrum, loss-function, reflectivity and conductivity of the undoped SnO2 in two polarization directions are compared with both previous calculations and measurements. 相似文献
223.
膨润土负载掺铁氧化钛光降解苯酚 总被引:1,自引:0,他引:1
以钛酸四丁酯为原料,用溶胶-凝胶法制备了以膨润土为载体的负载型TiO2光催化剂;采用分光光度法测试其光降解性能;讨论了影响苯酚降解的主要因素。结果表明,在pH=8.0时,光催化剂的用量为15mg/L,苯酚溶液的浓度为5mg/L时,光照时间为120min,苯酚的降解率可达98.2%。 相似文献
224.
报道了基于掺氧化镁的周期性极化铌酸锂(PPMgLN)光学参量产生器的研究。采用1064nm声光调Q准连续Nd:YAG激光器作为泵浦源,重复频率为4.3kHz。光学参量晶体PPMgLN的周期为30.7μm。采用温度调谐,调谐的范围为30℃~180℃,输出信号光的调谐范围为1561nm~1672nm,最高输出功率为180mW,相应的1064nm光的泵浦功率为1.017W,光光转换效率为17.7%。 相似文献
225.
稀土配合物RE(TPTZ)Cl3的合成、表征及荧光性能研究 总被引:1,自引:0,他引:1
首次以2,4,6-三吡啶基三嗪(TPTZ)与Sm, Eu, Tb和Dy氯化物反应,合成四种单一稀土配合物以及Tb分别1∶1掺Gd, Y, La的三种异核配合物。经元素分析、稀土络合滴定、摩尔电导率、红外光谱、紫外光谱和差热-热重测定表明,配合物的组成分别为RE(TPTZ)Cl3·3H2O(RE=Sm, Eu, Tb, Dy)和Tb0.5Ln0.5(TPTZ)Cl3·3H2O(Ln=Gd, Y, La);TPTZ作为三齿配体与稀土离子配位,即中心环提供一个N原子,两个吡啶环分别提供一个N原子;配合物中3个水分子与稀土离子配位,1个Cl-在外界,2个在内界,为1∶1型电解质;配合物内外界可能为[RE(TPTZ)(H2O)3Cl2] Cl,稀土离子的配位数为8。配合物的荧光光谱测试表明,四种单一稀土配合物中,Tb配合物发光最强;三种1∶1掺杂异核Tb配合物荧光强度大于纯Tb配合物,表明Y3+, La3+和Gd3+都可以敏化Tb3+的发光,其中Gd3+的敏化作用最强,Y3+次之,La3+最差。 相似文献
226.
227.
In this paper we investigated the vibrational properties of (Fe,Li)-doped delafossite oxide CuCrO2 by means of Raman experiments. The measurements were carried out at ambient temperature and pressure and on ab- and a(b)c-plane of a single grain. The samples were prepared using self-combustion urea nitrate process and the structure of all samples was checked using X-ray diffraction. All peaks were indexed as arising from CuCrO2 delafossite with space group R-3 m. Active phonon modes with A1g and Eg symmetries were identified as well as the presence of one additional line that could not be associated with inhomogeneities at microscopic level. The frequencies of the A1g and Eg modes were also observed to be independent upon Fe and Li doping, but not the corresponding scattering intensities. 相似文献