氧含量对磁控溅射Nb掺杂TiO_2薄膜结构与性能的影响

采用三靶磁控共溅射法在玻璃衬底上制备了Nb掺杂TiO_2透明导电薄膜。研究了在不同氧含量时薄膜的结构和光电性能。实验结果表明:氧含量的变化能改变Nb掺杂TiO_2薄膜晶体的晶粒尺寸、表面形貌、透光率和电阻率,当溅射氩气中通入2%氧气时,可得到性能最佳的锐钛矿相Nb掺杂TiO_2薄膜,所得薄膜可见光透过率高达80%,电阻率降至2.5×10~(-3)Ωcm。并且,Nb掺杂导致了TiO_2薄膜的吸收限产生蓝移,且蓝移程度随氧含量的改变而有所不同。研究认为,氧含量改变了Nb掺杂TiO_2薄膜晶体的结构形貌以及Nb杂质和氧空位提供的有效载流子浓度,从而直接影响了Nb掺杂TiO_2薄膜的光电性能。     

Sm2O3掺杂BaTiO3陶瓷的结构与电性能研究

采用溶胶-凝胶法制备了掺杂不同浓度Sm2O3(分别为0.001,0.002,0.003,0.005,0.007mol)的BaTiO3陶瓷,并对其结构与电性能进行了研究.结果表明:Sm2O3掺杂BaTiO3陶瓷的晶型在室温下为四方相,而且随着Sm2O3掺杂浓度的增加,BaTiO3陶瓷的晶粒尺寸变小,说明Sm2O3掺杂对BaTiO3陶瓷晶粒的生长有一定的抑制作用;Sm2O3掺杂BaTiO3陶瓷的电阻率比纯BaTiO3陶瓷明显下降,当添加量为0.001mol时,电阻率最小,.从4.3×109Ω·m下降为6.536×103Ω·m;Sm2O3掺杂BaTiO3陶瓷的晶粒电阻随着温度的变化,呈现NTC效应,而晶界电阻随着温度的变化,呈现PTC效应,且晶界电阻远远大于晶粒电阻,说明该材料的PTC效应是由晶界效应引起的.     

新型ZnO陶瓷线性电阻材料

本文研究了少量ＭｇＯ，Ｌａ２Ｏ３，ＺｒＯ２等对ＺｎＯ陶瓷线性电阻材料晶粒生长速度和最终晶粒尺寸的影响规律，以及极微量掺杂Ｌｉ２Ｏ对晶粒和晶界电阻率的影响规律，实验表明，ＭｇＯ，Ｌａ２Ｏ３和ＺｒＯ２都能使ＺｎＯ陶瓷伏安特性线性化，在一定添加量范围内，ＭｇＯ的添加量不影响陶瓷线性电阻的电阻率，Ｌａ２Ｏ３和ＺｒＯ２的添加量都能有效地控制陶瓷线性电阻的电阻率，ＭｇＯ的添加量不影响ＺｎＯ陶瓷的晶粒生长速度，     

Sm2O3掺杂BaTiO3陶瓷的结构与电性能研究

采用溶胶-凝胶法制备了掺杂不同浓度Sm₂O₃(分别为0.001,0.002,0.003,0.005,0.007mol)的BaTiO₃陶瓷,并对其结构与电性能进行了研究.结果表明:Sm₂O₃掺杂BaTiO₃陶瓷的晶型在室温下为四方相,而且随着Sm₂O₃掺杂浓度的增加,BaTiO₃陶瓷的晶粒尺寸变小,说明Sm₂O₃掺杂对BaTiO₃陶瓷晶粒的生长有一定的抑制作用;Sm₂O₃掺杂BaTiO₃陶瓷的电阻率比纯BaTiO₃陶瓷明显下降,当添加量为0.001mol时,电阻率最小,.从4.3×109Ω·m下降为6.536×103Ω·m;Sm₂O₃掺杂BaTiO₃陶瓷的晶粒电阻随着温度的变化,呈现NTC效应,而晶界电阻随着温度的变化,呈现PTC效应,且晶界电阻远远大于晶粒电阻,说明该材料的PTC效应是由晶界效应引起的.     

Nb掺杂对（Sr,Pb）TiO3基陶瓷半导体晶粒及晶界导电特性的影响

研究了施主掺杂的（Ｓｒ，Ｐｂ）ＳｉＯ３陶瓷，探讨不同的施主Ｎｂ掺杂浓度对材料电阻率和显微结构的影响，通过复阻抗解析，分别得到施主浓度的变化对材料晶粒和晶界电阻率的影响规律。结果表明随施主浓度的增加，晶粒和晶界电阻率变化呈现相似的Ｕ型曲线，但晶界的电阻率值及变化幅度远大于晶粒，证明了晶界对材料的电阻特性起主导作用。     

施主掺杂BaTiO_3陶瓷中电阻率、晶粒尺寸与氧分压的关系

施主含量不同的 BaTiO_3陶瓷在 H_2气氛中烧结后具有相近的平均晶粒直径。在大气中氧化后,它们仍然具有典型的 U 形电阻率～施主掺杂浓度曲线。这与传统理论不完全一致。本文就晶粒尺寸随氧分压的变化关系提出了新的见解。     

(Ba-Pb)TiO_3固溶体为基的PTCR材料及其微观结构

在(Ba—Pb)TiO_3固溶体系统中采用混合氧化物工艺制备了铁电相变温度为300℃的 PTCR 材料,其性能为:室温电阻率10~4Ω·cm;电阻率在300℃附近突变10~3;体积密度6.45g/cm~3(～94%)。通过对样品的扫描电镜观察,研究了在该系统中材料的化学组成(添加物)、微观结构和宏观电性能之间的一些关系。过量 BaO、Al_2O_3和 SiO_2是本系统的有用添加物,因为它们能使材料的微观结构比较精细;Mn~(2+)起了受主杂质的作用,它能增加材料的电阻率和电阻率～温度曲线的斜率,但是有时它会促进晶粒生长;过量 TiO_2在本系统中并不适宜,因为会产生粗晶的微观结构。本实验结果清楚地表明,样品的 PTCR 性能与它们的微观结构密切相关。     

钛酸锶的还原工艺和晶粒性质

将纯钛酸锶陶瓷和石墨粉放入加盖坩埚内加热，可使晶粒电阻率降低至９．２３Ωｃｍ；而晶界呈电容性，其电阻比晶粒大五十倍。在氢气氛中将钛酸锶陶瓷还原，则晶界近于短路。用极化子跳跃导电对晶粒的电感性作了解释。     

用溶胶-凝胶法制备的纳米 TiO_2粉末的结构

本文采用溶胶-凝胶法制备出纳米 TiO_(2)粉末,并通过热重分析(TG)、差示扫描量热分析(DSC)、X 射线衍射(XRD)、透射电镜(TEM)等实验手段研究了其微观结构及形貌随着热处理温度(T_a)变化的规律。当热处理温度低于500℃时,TiO_2粉末的平均晶粒和颗粒尺寸均小于20nm,所有晶粒均为锐钛矿结构。当热处理温度高于550℃时,TiO_2颗粒及晶粒迅速长大,并且样品中开始出现金红石结构的TiO_2晶粒。当热处理温度高于800℃时,样品中所有晶粒均为金红石结构。     

SrTiO3为基的介质陶瓷的结构与介电性质

本文主要研究0.91(Sr_(0.84)Pb_(0.16))TiO_(?) 0.09(Bi_2O_3·3.5TiO_2)介质陶瓷的结构与介电性质。用扫描电镜和 X 射线衍射分析表明,此种材料在室温下为顺电立方相,具有晶粒小且均匀、致密度高等特点。介电测量表明,在10kHz～90MHz 范围内样品的介电常数ε′基本上保持不变,而介电常数ε″随频率的增加而平坦地增大。     

TiO2和MgO微量添加剂对Al2O3陶瓷烧结致密化的影响

通过在氧化名中添加微量氧化钛和氧化镁,利用无压烧结工艺,制备了具有明显各向异性晶粒的氧化铝块材,研究了氧化钛、氧化镁的添加量和烧结温度对材料显微结构和致密度的影响,与单纯添加氧化钛的氧化铝材料相比,氧化镁的加入细化了氧化铝的晶粒,因此,可以通过调整氧化镁的加入量,在保持氧化铝晶粒各向异性形貌的同时,调整晶粒的尺寸,最终得到比较均匀的显微结构。     

Ag掺杂对TiO2粉末结构的影响

采用溶胶-凝胶工艺制备了Ag掺杂的TiO2粉末。通过XRD、SEM、EDX、DSC-TG、BET氮吸附法等研究了Ag掺杂对TiO2结构的影响，结果发现掺杂的Ag降低了TiO2锐钛矿向金红石相转变的温度，促进了相转变。适量掺杂时，Ag抑制了锐钛矿粒子的生长，结果使锐钛矿粒子的粒径降低，TiO2粉末的比表面积增加。     

Microstructure development in Sb2O3-doped ZnO

The microstructure development in Sb₂O₃-doped ZnO was studied at doping levels up to 2.0 mol%. Dopant Sb₂O₃ reacted with ZnO to form inclusion particles,α-Zn₇Sb₂O₁₂, and inhibited the grain growth of ZnO. With increasing doping level of Sb₂O₃, the growth rate of ZnO decreased whereas that of inclusion particles increased. Some inclusion particles were trapped in ZnO grains at low doping levels of Sb₂O₃, but the volume fraction of trapped inclusion particles decreased with increasing doping level. Stereological analysis of the size and number ratios of ZnO grains and inclusion particles indicated that a compatible assumption is needed to evaluate Zener effect in two-phase sintering.     

Nb掺杂TiO2压敏陶瓷的施主掺杂固溶度

研究了不同烧结温度TiO2压敏陶瓷的显微结构、施主掺杂固溶度和电学性能。采用SEM和EDS测试了其显微结构和晶粒化学组成。随烧结温度增加,TiO2晶粒迅速长大,显微结构均匀致密,但过高的烧结温度将导致较多气孔。1350℃为比较合适的烧结温度,其晶粒大小为15μm左右。在施主掺杂浓度一定的条件下,施主掺杂离子Nb5+在TiO2晶粒中的固溶度、晶粒电子浓度和电导率随烧结温度上升而增加,晶粒电阻率随烧结温度上升而下降。以能谱中O为参考确定TiO2晶格数量计算得到的固溶度及其电学性能更符合实验测试结果。     

Cathodoluminescence study of SnO2 powders aimed for gas sensor applications

In this paper we report on cathodoluminescence (CL) spectra of SnO₂ powders, synthesized using the wet chemical route. The analysis of influence of the modes of calcination (T_an-450–800 °C), and doping by both Pd and Pt (0.01–10.0 wt.%) on CL spectra was made. It was found that the measurement of CL spectra could be an effective research method of nanostructured metal oxides, aimed for gas sensor applications. It was established that in nanocrystalline SnO₂ the same system of energy levels, associated with radiative recombination, as in single crystalline and polycrystalline SnO₂, is retained. It was found that doping by both Pd and Pt modifies the structural properties of SnO₂ grains. Also, there is an optimum doping; near 0.1–0.2 wt.%, at which a maximum intensity of cathodoluminescence is reached. It was concluded that for low concentrations of both Pd and Pt additives in SnO₂ an improvement of the material's crystal structure is promoted, and is associated with a decrease in the non-radiating recombination rate.     

Visible light irradiated photocatalytic and magnetic properties of Fe-doped SnS<Subscript>2</Subscript> nanopowders

Fe-doped SnS₂ (SnS₂:Fe) nanopowders were synthesized by cost effective chemical method and characterized by thermo gravimetric-differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and vibrating sample magnetometer techniques. The photocatalytic activity was evaluated for the degradation of congo red dye under visible light irradiation. XRD studies indicate that both the undoped and doped SnS₂ nanopowders exhibit hexagonal crystal structure with a strong (1 0 1) preferential growth. Nanosized grains are evinced from the TEM images. XPS spectra confirmed the presence of Fe in the doped samples. Photodegradation efficiency increased with increase in Fe doping concentration and the SnS₂:Fe nanopowder with 10 wt% Fe doping concentration exhibits a maximum efficiency of 93.94% after 180 min light irradiation. Ferromagnetic ordering of pure SnS₂ improved with Fe doping. The outcome of the results indicated that Fe-doped SnS₂ nanopowders are well suited as diluted magnetic semiconductor and also can be used as an efficient photocatalyst.     

The effect of doping process on microstructure and dielectric properties of BaTiO3-based X7R materials

The effect of doping process on the dielectric properties, sintering behavior and microstructure were investigated on the BaTiO₃–Nb₂O₅–Co₃O₄ ternary system ceramic. Temperature stable dielectric ceramics were obtained by different doping processes if only appropriate Nb⁵⁺+Co³⁺ amount and Nb⁵⁺/Co³⁺ ratio were adopted. The dielectric constant was enhanced to the largest extent by nanometer oxide doping and the temperature characteristic satisfied the X7R specification. Two kinds of grains were observed in all the samples: matrix grains (BaTiO₃) and the secondary phase grains (Ba₆Ti₁₇O₄₀) formed by the incorporation of Nb⁵⁺ and Co³⁺ into BaTiO₃ lattice and Ti⁴⁺ segregation. The matrix grains were about 1 m in diameter and showed little grain growth with increasing temperature in all the doped samples, whereas the sizes of the secondary phase grains were strongly dependent on the doping process. The secondary phase formed liquid phase during firing, but the liquid phase contributed little to the densification of ceramics.     

Li-Cu共掺杂ZnO纳米薄膜的溶胶凝胶法制备

采用溶胶-凝胶法,通过调整氯化锂和氯化铜的摩尔比在不同基片上制备了不同Li-Cu共掺杂浓度的ZnO薄膜.利用X射线衍射仪、扫描电子显微镜、透射电子显微镜、紫外可见光分光光度计和伏安特性测试等表征了薄膜的结晶状况、表面形貌及光电特性.结果表明:所得Li-Cu共掺杂ZnO薄膜为六角纤锌矿多晶结构,有CuO杂质相生成.随Li和Cu摩尔比增加,共掺杂ZnO薄膜结晶度增强,晶粒长大,样品表面不平整度增加.CuO颗粒的出现,使得共掺杂ZnO薄膜透射率降低,透光性较差.Li与Cu摩尔比为1∶1时,共掺杂ZnO薄膜的综合导电性最好.     

La和Nb共掺提高BiFeO3的磁学性能

采用溶胶-凝胶法成功制备了Bi1-xLaxFe0.99Nb0.01O3(x≤0.25)纳米颗粒样品,并研究了La和Nb共掺对BiFeO3样品的晶体结构、晶粒尺寸和磁学性质的影响.根据X射线衍射及Rietveld精修结果可知,所有样品都保持R3c空间结构,且Fe-O-Fe键角随着La掺杂量的增加而减小.XPS测试结果表明,La和少量Nb共掺不会引起样品中Fe3+和Fe2+含量的明显变化.磁性测量发现剩余磁化强度强烈依赖于La掺杂量x.La掺杂影响着反向旋转的FeO5八面体结构变化,而Nb离子掺杂会导致样品晶粒细化.共掺BiFeO3的磁性增强是两种影响机制协同作用的结果.     

Interfacial Structure of Nanocrystalline SnO2 and SiO2-doped SnO2

Tindioxideisoneofthemostimp0rtantmaterialsforsens0rs.Inthisletter,theinterfacialstructuresofn-SnO2andn-Si-SnO2(d0pedwith5wtpctSiO2)samplespreparedbythesol-gelpr0cesshavebeenin-vestigatedbyX-raydiffraction(XRD),p0sitronlife-timespectr0sc0pyand119SnM6ssbauerspectr0scopy.Variati0nsofgrainsizeforn-SnO2andn-Si-SnO2sampleswithsinteringtemperatureshowthatthegrowthhastw0stageswithincreasingtempera-ture.Thecrystallizationtemperatureisab0ut5O0'C.Whenthesinteringtemperaturewaslowerthanthecrystall…