TbYbBiIG晶体在1500～1620nm波段的带宽和温度特性研究

以B i2O3/B2O3为主助熔剂和加速坩埚旋转技术改进的高温助熔剂法生长出掺B i复合稀土铁石榴石TbxYbyB i3-x-yFe5O12单晶.研究了该系列晶体材料在近红外通信波段(波长λ=1500~1620nm)处的磁光性能,其中Tb0.91Yb1.38B i0.71Fe5O12单晶有大的比法拉第旋转角-1671.2°/cm(λ=1550nm,25℃),小的饱和磁化强度(4πM s=0.6×106A/m),小的法拉第旋转温度系数(FTC=3.92×10-5/K,λ=1550nm),在λ=1500~1620nm波长范围的法拉第旋转波长系数FWC(25℃)为0.009%/nm,在λ=1500~1620nm波长和25~95℃温度范围内反向隔离度>40dB.综合性能表明TbxYbyB i3-x-yFe5O12适合用作光通讯系统中宽带和温度稳定的高性能光隔离器的法拉第转子材料.     

石榴石单晶薄膜磁光调制器

磁光调制器是利用偏振光通过磁性介质使偏振面产生旋转——法拉第效应来调制光束.我们采用液相外延生长的(Bi,Tm)_3(Fe,Ga)_5O_(12)单晶薄膜,制成磁光调制器,在音频范围效果良好.我们用单     

(Bi,Yb)4Ti3O12薄膜退火研究

采用溶胶-凝胶旋涂法在Pt(111)/Ti/SiO2/Si(100)基底上成功地沉积出(Bi,Yb)4Ti3O12[Bi3.4Ybo.6Ti3O12,BYT]铁电薄膜.系统地研究了退火温度对BYT铁电薄膜的晶体结构、表面形貌以及铁电性能(剩余极化强度)的影响.揭示了退火温度对BYT薄膜的晶体结构、表面形貌以及铁电性能有着明显的影响,给出了最佳退火温度为700℃左右.     

制备Nd3+:Gd3 Ga5O12透明陶瓷的纳米粉体

由于激光晶体的生长周期长、成本高等缺点,激励人们不断地探索新的激光材料。透明陶瓷就是最近发展起来的一种。采用溶胶-凝胶法合成了用于制备掺钕的钆镓石榴石(Nd3 ∶Gd3Ga5O12)透明激光陶瓷的多晶纳米粉体。采用X射线衍射(XRD)和扫描电子显微镜(SEM)对样品的晶相和形状进行了分析。结果表明,温度为1000℃,灼烧12 h,获得单分散、形状规则、似球形的Gd3Ga5O12(GGG)纳米粉体,且随着烧结温度的提高前驱粉体粒度不断增加。荧光发射的最强峰位于1062.7 nm处,对应于Nd3 的4F3/2→4I11/2能级跃迁。     

(Bi,Yb)4Ti3O12铁电薄膜的制备

采用稀有金属镱元素对钛酸铋进行掺杂,以期获得性能较好的(Bi,Yb)4Ti3O12铁电薄膜.采用溶胶-凝胶旋涂法在p型Si(100)基底上成功地沉积出(Bi34,Yb06)Ti3O12[BYT]铁电薄膜.用X射线衍射法对其结构及其成份进行了表征,用铁电分析仪(RT66A)测试了其铁电性.并就影响BYT薄膜铁电性能的因素进行了分析.     

BiFeO_3/Bi_4Ti_3O_(12)多层铁电薄膜的性能研究

采用sol-gel法在FTO/玻璃底电极上制备了BiFeO3/Bi4Ti3O12多层薄膜。研究了室温下薄膜的结构,铁电和漏电流性质。结果表明,相对于纯的BiFeO3薄膜,BiFeO3/Bi4Ti3O12多层薄膜具有更低的漏电流,表现出较强的铁电性,在4.40×105V/cm的测试电场强度下,剩余极化强度为3.7×10–5C/cm2。在2.00×105V/cm的测试电场强度下,BiFeO3和BiFeO3/Bi4Ti3O12薄膜的漏电流密度分别为10–5和10–7A/cm2。     

升温速率对Bi_(0.98)La_(0.02)FeO_3-PbTiO_3薄膜结构性能的影响

采用sol-gel法在SiO2/Si(100)衬底上制备了0.68(Bi0.98La0.02)FeO3-0.32PbTiO3(BLFPT)薄膜。采用快速退火技术,以2～40℃/s速率升温、在700℃下保温100s对BLFPT薄膜进行了后续处理。研究了升温速率对BLFPT薄膜结构性能的影响。XRD测试结果显示BLFPT薄膜为赝立方结构。SEM和AFM结果表明,当升温速率为2℃/s时,BLFPT薄膜表面晶粒更为均匀致密,粗糙度最小。XPS分析显示,Bi、Fe和Ti分别主要以化合态Bi2O3、Fe2O3和TiO2的形式存在。     

铽镓石榴石晶体多晶合成与单晶生长研究

以(99.99%)Ga2O3和Tb4O7为原料,按照化学计量比并适当富镓配料,采用固相反应法(分段升温工艺)合成高纯、单相的铽镓石榴石(Tb3Ga5O12,简称TGG)多晶料。使用提拉法(CZ)成功生长出44mm×70mm,外观完整无开裂、无螺旋的TGG晶体。经X线衍射分析、密度测试、晶体成分测试表明,生长的晶体结构完整,结晶性好;晶体的密度为7.14g/cm3,与理论值接近;晶体中Tb与Ga摩尔比为66%,可能存在少量Ga空位。     

Yb掺杂原子数分数为0.5%的Yb∶Y_3Al_5O_(12)晶体的光谱分析

采用提拉法生长了Yb掺杂原子数分数为0.5%的Yb∶Y3Al5O12(Yb∶YAG)晶体,对晶体的吸收光谱和荧光光谱进行了分析。与Yb掺杂原子数分数为5%的Yb∶YAG晶体进行了对比,得出采用940 nm激光二极管(LD)抽运晶体最为合适。原子数分数为0.5%的Yb∶YAG晶体相对于原子数分数为5%的Yb∶YAG晶体自吸收效应的影响要小。测量了原子数分数为0.5%的Yb∶YAG晶体的荧光寿命为0.95 ms,与理论值很接近。因此采用原子数分数为0.5%的Yb∶YAG晶体作为激光工作物质将有利于高效、小型集成化的固体激光器的发展。     

Bi_(3.5)Yb_(0.5)Ti_3O_(12)铁电薄膜的制备及性能

采用溶胶-凝胶(Sol-Gel)法在Pt(111)/Ti/SiO2/Si(100)基片上淀积了Bi3.5Yb0.5Ti3O12(BYT)铁电薄膜,研究了在不同退火温度下形成的BYT薄膜的微观结构以及铁电性能方面的区别。结果发现,在610,660,710和760℃不同温度下退火的BYT薄膜的结晶度不同,退火温度越高的BYT薄膜,其结晶度越高。并且发现,BYT薄膜的剩余极化值(2Pr)在710℃以下随退火温度增高而增大,在710℃达到最大;在外加400kV/cm电场时2Pr为36.7μC/cm2,然后随退火温度上升又有所下降。     

（YbTbBi）_3Fe_5O_（12）块状单晶生长及其磁光性能

用助熔剂法生长出（ＹｂＴｂＢｉ）３Ｆｅ５Ｏ１２块状单晶，测量了该单晶在１．０～１．７μｍ范围的Ｆａｒａｄａｙ旋转谱及透射谱．当温度为１０～８０℃，λ＝１．５５μｍ时，测得该单晶的Ｆａｒａｄａｙ旋转温度系数为２．０×１０－２．（°）·ｍｍ－１·Ｋ－１．所得结果表明：（ＹｂＴｂＢｉ）３Ｆｅ５Ｏ１２单晶既有较大的Ｆａｒａｄａｙ旋转角，又有很小的温度系数     

Structural and magnetic properties of Dy3+ doped Y3Fe5O12 for microwave devices

The Dy³⁺ doped Y_3−xDy_xFe₅O₁₂ (x=0–3) nanopowders were prepared using microwave hydrothermal route. The structural and morphological studies were analyzed using transmission electron microscope, X-ray diffractometer and field emission scanning electron microscope. The nanopowders were sintered at 900 °C/90 min using microwave furnace. Dense ceramics with theoretical density of around 95% was obtained. Ferro magnetic resonance (FMR) spectrum and microwave absorption spectrum of Dy³⁺ doped YIG were studied, the signal exhibits a resonance character for all Dy³⁺ variations. It was observed that the location of the FMR signal peak at the field axes monotonically shifts to higher field with increasing Dy³⁺ content. The dielectric and magnetic properties (ε′, ε′′, µ′ and µ′′) of Dy³⁺ doped YIG were studied over a wide range of frequency (1–50 GHz). With increase of Dy³⁺ both ε′ and µ′ decreased. The low values of dielectric, magnetic properties and broad distribution of FMR line width of these ceramics are opening the real opportunity to use them for microwave devices above K- band frequency.     

Nanowire Structural Evolution from Fe3O4 to ϵ‐Fe2O3

The ?‐Fe₂O₃ phase is commonly considered an intermediate phase during thermal treatment of maghemite (γ‐Fe₂O₃) to hematite (α‐Fe₂O₃). The routine method of synthesis for ?‐Fe₂O₃ crystals uses γ‐Fe₂O₃ as the source material and requires dispersion of γ‐Fe₂O₃ into silica, and the obtained ?‐Fe₂O₃ particle size is rather limited, typically under 200 nm. In this paper, by using a pulsed laser deposition method and Fe₃O₄ powder as a source material, the synthesis of not only one‐dimensional Fe₃O₄ nanowires but also high‐yield ?‐Fe₂O₃ nanowires is reported for the first time. A detailed transmission electron microscopy (TEM) study shows that the nanowires of pure magnetite grow along [111] and <211> directions, although some stacking faults and twins exist. However, magnetite nanowires growing along the <110> direction are found in every instance to accompany a new phase, ?‐Fe₂O₃, with some micrometer‐sized wires even fully transferring to ?‐Fe₂O₃ along the fixed structural orientation relationship, (001) ∥ (111), [010] ∥ <110>. Contrary to generally accepted ideas regarding epsilon phase formation, there is no indication of γ‐Fe₂O₃ formation during the synthesis process; the phase transition may be described as being from Fe₃O₄ to ?‐Fe₂O₃, then to α‐Fe₂O₃. The detailed structural evolution process has been revealed by using TEM. 120° rotation domain boundaries and antiphase boundaries are also frequently observed in the ?‐Fe₂O₃ nanowires. The observed ?‐Fe₂O₃ is fundamentally important for understanding the magnetic properties of the nanowires.     

钆镓石榴石透明陶瓷纳米粉体的制备

以碳酸盐作沉淀剂,采用液相共沉淀法合成了Gd2Ga5O12(GGG)透明陶瓷纳米粉体,并利用热重-差热分析(TG-DTA)、X-射线衍射(XRD)、透射电子显微镜(TEM)、红外光谱分析等测试手段对前驱体及烧成粉体的结构和形貌进行了分析表征.XRD分析结果表明,在900℃下煅烧2h就可得到GGG纯相,属于立方晶体结构,其空间群为Ia3d,晶格常数a=1.2376 nm;TEM测试结果发现,此法可获得分散性良好、形状规则类似球形的纳米粉体,粒度大小约为60 nm.     

Nd3 :Gd3Ga5O12激光晶体的吸收与发光

测量了用提拉(CZ)法生长的Nd3+Gd3Ga5O12(NdGGG)激光晶体室温时的吸收光谱,其中在806 nm处的吸收系数最大(α＝5.12 cm-1),吸收截面为4.03×10-20 cm2.用806 nm激发分别得到室温和10 K时的荧光光谱和荧光寿命,其中在1.06 μm附近晶体的荧光发射强度最强,2种温度时的峰值发射截面分别为1.7×10-19 cm2和1.9×10-19 cm2.0.6 at%和1.0 at%2种Nd3+掺杂浓度的晶体,室温时的荧光寿命分别为251 μs和240 μs,10 K温度时分别为253 μs和241 μs.与NdYAG晶体的荧光寿命、浓度猝灭效应和发射截面进行了比较,对结果进行了分析与讨论.     

纳米氧化铁粉体的溶胶-凝胶法制备

以硫酸亚铁为原料,柠檬酸为螯合剂,通过溶胶-凝胶法制备Fe2O3纳米粒子,采用X-射线衍射(XRD)和差重-热重(TG-DTA)分析研究了Fe2O3晶相的形成过程,用扫描电镜(SEM)对所制得粉体的表面形貌进行了分析.结果表明,煅烧温度应高于520 ℃,所制备纳米粉体为α-Fe2O3,为球形颗粒,Fe2O3粉体粒度随煅烧温度的升高而增大,煅烧温度为600 ℃时,可获得30 nm的α-Fe2O3颗粒,粉体颗粒大小均匀,分散性好.     

Synthesis and Characterization of Ferroferriborate (Fe3BO5) Nanorods

Fe₃BO₅ nanorods with diameters from 4 nm to 16 nm and length from 43 nm to 60 nm are synthesized by a facile thermal decomposition of iron acetylacetonate and t‐butylamine borane (TBAB). TBAB is used to control the 1D growth and the aspect ratio of the nanorods. These Fe₃BO₅ nanorods are antiferromagnetic with T_N = 174 K, which is higher than that of bulk Fe₃BO₅ (114 K).     

NIR Mechanoluminescence from Cr3+ Activated Y3Al5O12 with Intense Zero Phonon line

Mechanoluminescence (ML) materials with long-wavelength emission bands are essential for future in vivo bioimaging, non-destructive testing of solids, etc. The lack of a defined mechanism, however, prevents the application of near infrared ML materials above 650 nm in several new fields. Here, the addition of Ga³⁺ ions to Y₃Al₅O₁₂: Cr³⁺ manipulates matrix microstructure evolution, boosting near-infrared (NIR) zero-phonon line (ZPL) stress optical output of the Cr³⁺ ion at 688 nm. The key factor changing the crystal field intensity D_q/B due to the addition of Ga³⁺ ions is what causes the luminescence amplification of ZPL. The ML fabricated by composite polydimethylsiloxane and Y₃Al₄GaO₁₂: Cr³⁺ (YAGG: Cr³⁺) may penetrate chicken feet epidermal tissue and 4 mm pork tissue thanks to the strong NIR ZPL emission of YAGG: Cr³⁺ phosphor. This discovery of enhancing near-infrared ZPL intensity by solid solution provides us with a new technique for optimizing NIR ML materials, as well as a new prospect for NIR ML materials in biological applications.     

Nd3+:Gd3Ga5O12单晶的能级和晶体场计算

测试了Nd3+:GGG单晶在可见和近红外波段的吸收光谱,并分析指认了它的实验能级,通过从头计算的DV-Xa方法计算得到了它的晶体场参数和旋轨耦合参数。用Nd3+:GGG在77K和300K的156个、88个实验能级,拟合了它的自由离子参数和晶体场参数,均方根误差（即拟合精度）σ分别为15.79和 11.48 cm-1。结果表明晶体场参数的拟合结果和从头计算值符合的很好。最后比较了拟合得到的Nd3+:GGG和已报道Nd3+:YAG 的自由离子参数和晶体场参数。