用聚合物前驱体法低温合成铌酸锂纳米粉体

用聚合物前驱体法,以柠檬酸为配位剂．乙二醇为酯化剂．水为溶剂合成纳米铌酸锂（LiNbO3）粉体。研究发现：当柠檬酸和金属离子的摩尔比（下同）为3：1,柠檬酸和乙二醇的为1：2时,可形成稳定的Li-Nb前驱体溶液和凝胶。用差热-热重分析研究凝胶前驱体的热分解历程。用X射线衍射分析和红外光谱分析研究凝胶前驱体及其不同温度下煅烧所得粉体的相组成和结构。结果表明：Li-Nb凝胶前驱体在加热过程中分解形成LizCO3相．Li2CO3与Nb2O3发生固相反应生成LiNbO3。凝胶前驱体经800℃煅烧2h可以制备纯钙钛矿型的纳米LiNbO3粉体。     

聚合物前驱体法制备铌酸钾钠纳米粉体

采用聚合物前驱体法,以柠檬酸(CA)为络合剂,乙二醇(EG)为酯化剂合成了纳米级(Na0.35K0.65)NbO3。研究了乙二醇用量对聚合物前驱体稳定性的影响,结果表明n(EG):n(CA)为2时能得到稳定凝胶,与乙二醇和柠檬酸聚酯化反应得到凝胶的理论配比一致。XRD分析表明聚合物前驱体在650℃煅烧2h可制得平均晶粒尺寸为24nm左右,纯单斜相结构的(Na0.35K0.65)NbO3纳米粉体,该合成温度比传统固相法降低了约300℃。     

铌酸钾锂薄膜的制备方法与研究进展

铌酸钾锂具有良好的光电、压电及非线性光学性能,在集成光学、集成电路等领域具有广阔的应用前景.综述了近年来铌酸钾锂薄膜的制备方法与最新进展,同时对各种方法制备的铌酸钾锂薄膜的研究结果进行了综述,并指出了目前研究存在的问题及其发展趋势.     

铌酸锂单晶光纤的生长

用导模法生长成功φ0.5×(160—170)mm各种取向的LiNbO_3单晶光纤。研究了单晶光纤形貌和生长参数的关系。比较了α轴和c轴LiNbO_3单晶光纤在生长速度、抗张强度上的差别。对c轴光纤单畴结构的形成机制进行了简单讨论。     

尖晶石型锰酸锂前驱体的表征与分解活化能

采用不同升温速率的差热分析研究空气气氛中锰酸锂前驱体分解的反应. 利用Doyle- Ozawa法和Kissinger法计算各反应阶段的表观活化能. X射线衍射、粒度分析、扫描电镜和透射电镜分析表明，共沉淀法和煅烧法相结合制备的LiMn2O4物相纯净，粒度分布均匀，形貌规整.     

低温合成超细铌酸锂粉末

以五氧化二铌和乙酸锂为原料,采用热分解法制备LiNbO3粉末。通过对LiNbO3粉末进行XRD表征,结果表明:当焙烧温度为400℃时,得到的产物为单相的LiNbO3粉体。在400℃焙烧下得到的LiNbO3粉体,通过扫描电镜(SEM)判断其粒径在100nm左右,在FT-IR谱图中440cm-1处存在Nb-O键的特征吸收峰。     

坩埚下降法生长铌酸锂晶体

采用坩埚下降法,生长了直径为5 cm的铌酸锂晶体.探讨了晶体生长工艺条件,测试了晶体的透过光谱.所得晶体呈浅茶色,分析认为主要是氧空位缺陷所致.铌酸锂晶体通常用作声表面波(surface acoustic wave,SAW)器件的基片,氧空位缺陷可增加基片的电导率,减少器件制造过程中晶片开裂,有利于提高SAW器件成品率.     

Surface plasmon resonance triggered promising visible light photocatalysis of LiNbO3 ceramic supported Ag nanoparticles

LiNbO₃ ceramic was fabricated using solid-state reaction route. Silver nanoparticles (NPs) were loaded on LiNbO₃ at room temperature using silver nitrate and polyethylene glycol reagents, without the use of external heat and light energy. The X-ray diffraction showed only LiNbO₃ phase in Ag-loaded LiNbO₃ sample with no peak related to Ag metal due to small fraction of Ag loading. X-ray energy diffraction spectroscopy elemental color mapping confirmed the uniform loading of Ag metal on LiNbO₃ particles. Ag metal was loaded in the form of NPs as visualized under transmission electron microscope. Ag NPs-loaded LiNbO₃ showed enhanced absorption of visible light owing to the phenomenon of surface plasmon resonance (SPR). The loading of Ag NPs had no effect on the band gap energy of LiNbO₃ ceramic. X-ray photoelectron spectroscopy technique confirmed the metallic chemical state of Ag in Ag NPs-loaded LiNbO₃. Ag NPs-loaded LiNbO₃ degraded 97% rhodamine-B model dye from the solution when irradiated for 240 minutes under visible light. The dye degradation follows pseudo-first-order kinetic having k-value (kinetic rate constant) of as 0.013 min⁻¹. The ^•OH (hydroxyl) and (superoxide) radicals were the main active species behind the photocatalytic activity of Ag NPs-loaded LiNbO₃. Thus, Ag NPs-loaded LiNbO₃ could be a potential material for degrading organic dyes from water.     

LiNbO_3:Fe晶体中光写入平面光子晶格折射率调制度的变化规律

研究了利用光折变效应在掺铁铌酸锂(LiNbO3:Fe)晶体中制作平面光子晶格时折射率调制度△n与晶格周期∧的关系。实验结果表明,平面光子晶格折射率调制度△n同晶格周期∧息息相关,当晶格周期达到分裂周期时,折射率调制度分布规律会发生质的变化。     

环境友好型水基四氧化三铁磁流体的制备与表征

在超声辅助无惰性气体保护的条件下,采用氧化共沉淀和化学共沉淀相结合的方法成功制备了四氧化三铁纳米粒子。通过XRD、FTIR、SEM和TEM等对其进行表征,结果表明,制备的四氧化三铁纳米粒子具有较好的晶形结构,粒径约为7 nm。通过正交实验证明了超声时间是影响四氧化三铁纳米粒子粒径的主要因素;而Fe2+与Fe3+的摩尔比是影响四氧化三铁纳米粒子粒径的次要因素。用柠檬酸对四氧化三铁进行表面改性,制备了环境友好型水基磁流体;磁性结果显示,其矫顽力及剩磁均很低,表现出较好的超顺磁性。     

应用电泳沉积技术制备钛酸钡铁电陶瓷薄膜

采用电泳沉积技术在Pt电极基片上制备BaTiO3铁电陶瓷薄膜，探讨了电泳沉积过程中的控制因素（悬浮液体系，电场强度，料浆浓度，沉积时间等）对成膜性能的影响，并对薄膜材料的结构，性能进行了表征，实验结果表明；在1050℃（2h)的烧成温度下，经重复沉积一烧结2-3次可得到基本无缺陷的BaTiO3陶瓷薄膜，测量频率在1kHz，测量频率在1kHz时，室温（23℃）下的介电常数ε=2300，介电损耗tanδ=0.2。     

LiNbO3纳米晶形貌模拟及其最佳纳米尺度计算

采用量子化学计算软件Material Studio的Morphology模块,运用BFDH法则对三方LiNbO3颗粒的纳米晶形貌进行了预测,并探讨了其纳米化的最佳尺度。模拟计算显示三方LiNbO3纳米晶的（112）、（112）面为最易外显面,显示几率为45.85%。通过对其纳米晶尺度的探讨,得出三方LiNbO3纯组分的最佳粒径为130nm。     

Growth and characterization of large size lead-free ferroelectric K(Ta,Nb)O3 single crystal

Lead-free piezoelectric materials with excellent performance are greatly demanded for the environmental issues. The lead-free ferroelectric single crystals are therefore greatly concerned for their much higher piezoelectricity than the polycrystalline counterparts and the domain-tunable property. However, the growth of large size and high-quality lead-free ferroelectric crystals has always been a great challenge. In this work, a ferroelectric KTa_1-xNb_xO₃ (KTN) single crystal with an extremely large size of 25 × 25 × 37 mm³ was grown using the modified top-seeded solution growth method. The large size enabled us to carry out comprehensive investigations on the crystal. The complete sets of dielectric, piezoelectric, and elastic constants for the [001]_C-poled KTN crystal with quasi single domain state were determined. Results showed that the crystal exhibits high electromechanical coupling coefficients with k_t~0.642 and k₃₃~0.679. Furthermore, the orientation dependence of the piezoelectric, dielectric, and elastic properties was determined by the tensor matrix transformation technique, and the maximum d₃₃, , and k₃₃ were found along the polar direction [001]_C. This work not only provides important guidance for the growth technology of lead-free ferroelectric crystals but also offers essential datasets of lead-free alkali niobate system, which is of great importance for both theoretical studies and designs of electromechanical devices.     

SiO2超疏水薄膜的制备和性能表征

采用溶胶-凝胶法、相分离及自组装技术,以正硅酸乙酯(TEOS)为硅前体,在硅溶胶中添加聚丙烯酸(PAA)引发相分离,通过控制PAA的含量来控制相分离的程度,从而制备出表面微结构可控制的SiO2薄膜.研究了聚丙烯酸含量对薄膜表面微结构及接触角的影响.用扫描电镜(SEM)对薄膜表面进行了表征,结果表明,SiO2薄膜表面粗糙度随着聚丙烯酸含量的增加而增加.最后用三甲基氯硅烷(TMCS)进行化学气相修饰,形成TMCS自组装单分子层,制备出接触角达158°的超疏水SiO2薄膜.     

Anomalous photovoltaic effect in Bi(Ni2/3Ta1/3)O3-PbTiO3 ferroelectric solid solutions

Dense Bi(Ni_2/3Ta_1/3)O₃-PbTiO₃ (BNT-PT) ceramics were prepared by solid-state reaction method. Morphotropic phase boundary between tetragonal and rhombohedral phase was observed around the composition 0.38BNT-0.62PT, at which large photovoltages of 13.2V were obtained under 405 nm laser illumination with power density of 200 mW/cm². By B-site Ni²⁺ ions doping, the bandgap values of BNT-PT solid solutions were reduced to 2.25~1.85 eV, and the anomalous photovoltaic response was extended from the ultraviolet region to a wavelength of 550 nm at the visible light region.     

Tuning oxygen vacancy in LiNbO3 single crystals for prominent memristive and dielectric behaviors

Understanding and manipulating the behavior of oxygen vacancy in oxide materials are of vital importance for rejuvenating materials with novel functionalities. We herein report a exciting phenomenon of oxygen vacancies changing from an isolated state to a clustered state in LiNbO₃ single crystals. The clustering of the oxygen vacancies induces a relaxor-like dielectric anomaly and a first-order phase transition. The relaxor-like dielectric anomaly was argued to be a pseudo-relaxor behavior resulting from the combined contributions of a dipolar relaxation and a Maxwell-Wagner relaxation. The first-order phase transition was ascribed to be an electric-ferroelectric phase transition. Interestingly, a well-defined melting point of the oxygen-vacancy clusters was observed. At temperatures near the point, a small dc field can lead to resistance switching from a high resistance state to a low resistance state, yielding a prominent memristive effect with the OFF/ON ratio of 10². Our results underscore that controlling the oxygen vacancy state is a promising strategy to tailor the properties of oxides for novel device applications.