Cao.28Ba0.72Nb2O6单晶的光学常数及吸收特性

山大晶体所采用提拉法生长出新晶体铌酸钙钡.本文通过分光光度计和椭偏光谱仪分别测得室温下铌酸钙钡的透射率和折射率随波长的变化关系.透射率光谱显示该晶体在波长大于380nm的可见光谱区是透明的.色散关系表明此材料的双折射较大,在短波区域寻常光及非常光的折射率之差约为0.12.此外,由透射率曲线计算了可见光范围内铌酸钙钡的吸收系数.从而得到吸收系数的平方根与光子能量的函数关系曲线.通过对该曲线的研究,发现铌酸钙钡晶体吸收边以下对应的跃迁为间接跃迁,计算出间接跃迁的禁带宽度Eg以及声子能量Ep.     

Ca0.28Ba0.72Nb2O6单晶的光学常数及吸收特性

山大晶体所采用提拉法生长出新晶体铌酸钙钡。本文通过分光光度计和椭偏光谱仪分别测得室温下铌酸钙钡的透射率和折射率随波长的变化关系。透射率光谱显示该晶体在波长大于380nm的可见光谱区是透明的。色散关系表明此材料的双折射较大，在短波区域寻常光及非常光的折射率之差约为0．12。此外，由透射率曲线计算了可见光范围内铌酸钙钡的吸收系数。从而得到吸收系数的平方根与光子能量的函数关系曲线。通过对该曲线的研究，发现铌酸钙钡晶体吸收边以下对应的跃迁为间接跃迁，计算出间接跃迁的禁带宽度Eg以及声子能量Ep。     

Dramatically Enhanced Visible-light-responsive H_2 Evolution of Cd_(1-x)Zn_xS via the Synergistic Effect of Ni_2P and 1T/2H MoS_2 Cocatalysts

Photocatalytic hydrogen generation from water-splitting holds huge promise for resolving the current energy shortage and environmental issues.Nevertheless,it is still challenging so far to develop non-noble-metal photocatalysts which are efficient toward solar-powered hydrogen evolution reaction(HER).In this work,through an ultrasonic water-bath strategy combined with solvothermal and electrostatic assembly processes,we obtain homogeneous Cd_1-xZn_xS–Ni₂P–MoS₂ hybrid nano-spheres consisting of Cd_1-xZn_xS solid solutions decorated by Ni₂P and 1 T/2 H MoS₂ cocatalysts,which demonstrate excellent activity and stability for visible-light-responsive(λ>420 nm)H₂ production.Specifically,the Cd_1-xZn_xS-Ni₂P-MoS₂ nano-spheres with 2 wt%Ni₂P and 0.2 wt%MoS₂(CZ_0.7S–2 N–0.2 M)exhibit the optimal HER activity of 55.77 mmol·g^-1·h^-1,about 47 and 32 times more than that of CZ_0.7S and Pt–CZ_0.7S,respectively.The outstanding HER performance of Cd_1-xZn_xS–Ni₂P–MoS₂ can be ascribed to the presence of abundant HER active sites in Ni2 P nanoparticles and 1 T/2 H MoS₂ nanosheets as well as the effective transfer and separation of charge carriers.Moreover,the coupling sequence of cocatalysts in Cd_1-xZn_xS–Ni₂P–MoS₂ is found to be critical in the regulation of charge transfer pathways and thus the resultant photocatalytic efficiency.The results displayed here could facilitate the engineering of high-performance photocatalysts employing multi-component cocatalysts for sustainable solar-to-fuel conversion.     

具有准同型相界(MPB)组成的化合物(Sr1-x Bax)2NaNb5O15的晶体生长及性质研究

用Czochralski方法生长出铁电钨青铜型单晶(Sr1-xBax)2NaNb5O15(简称SBNN),晶体沿c轴方向生长.正交-四方相的准同型相界(简称为MPB)存在于x=0.45～0.50之间;SBNN晶体是不一致熔融的化合物,在晶体成长过程中,Sr2+的分凝系数比Ba2+的大,因此具有高浓度Ba2+的SBNN晶体很难生长.晶体的居里温度是243℃,在此温度下的相变是弥散的,随频率的增加,介电常数降低.     

Sol-gel法制备掺钕钛酸铅铁电薄膜

采用sol-gel法在P型Si(111)衬底上制备了Pb0.85Nd0.1TiO3(PNT) 薄膜.用X射线衍射技术研究了退火温度对薄膜结构和结晶性的影响.同时还研究了薄膜的介电、铁电和绝缘性能.结果发现在600℃下退火1h的PNT薄膜呈钙钛矿结构;在0～5V范围内,薄膜的漏电流密度小于1.00×10-5A/cm2;在±5V的偏压范围内,C-V记忆窗口宽度为2V;在零电压下,时间保持长达105～106s; 在室温100kHz下,其介电常数为31.60,介电损耗为0.12.     

Phase Structures of （K0.48Na0.52）0.945Li0.055Sb0.05Nb0.95O3 Piezoceramics

The phase structures of lead-free （K0.48Na0.52）0.945Li0.055Sb0.05Nb0.95O3 piezoceramics are studied based on the measurements of ferroelectric and dielectric properties as well as the analyses of x-ray diffraction pattern and energy dispersive spectroscopy. The poled samples exhibit orthorhombic structure whereas the surface and interior for unpoled samples exhibit tetragonal and tetragonal-orthorhombic coexistent structures, respectively. These results are in agreement with the relative permittivity-temperature curves and demonstrate that phase transitions can be induced by Na volatilization and poling process. The remnant polarization Pr measured at 20°C increases continuously with the increase of electric field in the range of 2000-4000V/mm. This indicates that the polymorphic structure is more beneficial to the rotation or reorientation of dipoles than either the orthorhombic or the tetragonal structure. The randomly oriented domains may be the essential reason for the continuous rotation or reorientation and not good thermal stability.     

氧化锌单晶的水热生长与结晶习性

本文应用水热生长法,采用双温区高压反应釜,黄金内衬(φ35mm ×2mm),碱性溶液矿化剂,生长出了毫米级的透明氧化锌单晶,最大单晶可达2mm ×3mm ×6mm.所生长氧化锌晶体为纤锌矿型的六方晶体,晶体呈上部锥形的六棱柱体,{10(1-)1}、{10(1-)0}和{000(1-)}面有较大的显露平面.本文中从温差和填充度方面研究了实验条件对ZnO晶体的生长及其形貌的影响,使用黄金内衬前后的结果表明,用贵金属内衬可以有效阻止釜内壁杂质的进入,使晶体完整透明.     

Diffuse dielectric anomaly of （Na0.5K0.5Bi）0.5TiO3 crystal at high temperature

This paper investigates the dielectric properties of (Na_0.5K_0.5Bi)_0.5TiO₃ crystal at intermediate frequencies (1kHz \le f \le 1MHz) in the temperature range of 30--560℃. A pronounced high-temperature diffuse dielectric anomaly has been observed. This dielectric anomaly is shown to arise from a Debye-like dielectric dispersion that slows down following an Arrhenius law. The activation energy E_r obtained in the fitting process is about 0.69eV. It proposes that the dielectric peak measured at low frequency above 400℃ is not related to the phase transition but to a space-charge relaxation.