Sr0.4Ba0.6Nb2O6物相形成过程的XRD分析

采用X射线衍射技术(Guinier-Hagg相机)分析了Sr0.4Ba0.6Nb2O6(SBN40)原始混合粉料经不同温度煅烧后的相组成,并利用PIRUM程序对不同反应温度下形成铌酸锶钡相的晶胞尺寸进行了计算.结果表明:在Sr0.4Ba0.6Nb2O6的形成过程中将出现中间相Na5Nb4O15、Sr5Nb4O15、SrNb2O6与BaNb2O6,而SrNb2O6与BaNb2O6最终反应生成铌酸锶钡.反应生成的铌酸锶钡的晶胞参数随反应温度的升高而变小.依据这些实验结果,文中提出了Sr0.4Ba0 6Nb2O6相的形成机制.     

原始粉料对Sr0.4Ba0.6Nb2O6烧结性能与显微结构的影响

对比了以单相Sr0.4Ba0.6Nb2O6为原料的常规烧结试样(SBN40)以及以SrNb2O6与BaNb2O6混合物为原料的反应烧结试样(RSBN40)的烧结性能与显微结构.结果发现,RSBN40试样的致密化速率较SBN40试样较慢,试样SBN40与RSBN40密度分别在1250与1300℃达到最大,其值分别为5.21与5.27g·cm-3.此外,当烧结温度高于1250℃时,试样SBN40比RSBN40易于出现异常晶粒长大现象.     

Ba0.6 Sr0.4 TiO3-ZnNb2O6复相微波介质陶瓷的结构与介电性能研究

以Ba0.6Sr0.4TiO3为基体材料,采用传统陶瓷制备工艺,制备了Ba0.6 Sr0.4 TiO3-ZnNb2O6(简称BSTZ)复相微波介质陶瓷.结果表明,BSTZ复相陶瓷可在1200℃烧结成瓷,烧结温度明显低于Ba0.6Sr0.4TiO3陶瓷的烧结温度,并反应生成新相BaNb3.6O10.在室温低频下,随ZnNb2O6含量的增加,BSTZ复相陶瓷的介电常数下降;在1.6kV/mm的直流偏压下,各BSTZ复相陶瓷的可调性随ZnNb2O6添加量增加而减小.     

SBN系列人工晶体的合成与初步研究

以SrNb2O6-BaNb2O6的赝二元体系相图为基础来合成这个体系中的3种物质,根据X射线粉晶衍射图谱中显示数据的分析,发现了相图中的端元相SrNb2O6、BaNb2O6和中间相Sr0.5Ba0.5Nb2O6在结构上的不连续性.计算了3种合成晶体的晶胞参数和化学分子式.     

M(M= Mg, Ca, Sr, Ba, Ni)Nb2O6的光催化性能的研究

应用固相烧结法制备了半导体光催化材料MgNb2O6,CaNb2O6,SrNb2O6,BaNb2O6,NiNb2O6粉体.利用XRD、UV-Vis漫反射谱、扫描电镜对上述粉体晶体结构、光谱性质和形貌进行了分析.在紫外光下对其降解罗丹明B（RhB）的光催化性能进行了评估.结果表明,碱土金属Sr、Ba对NiNb2O6中Ni的取代能很好地提高铌酸盐的光催化效果,在10h紫外光照射下能分别将RhB的浓度降解到原来的21%和37%.     

SrNb2O6/Nb2O5复合物光催化降解甲基橙的研究

光催化剂SrNb2O6采用传统固相反应分别在合成温度为950℃（低温）和1400℃（高温）进行制备.通过XRD粉末衍射和UV-Vis吸收光谱分析,表征了样品的物相和光谱吸收特性.通过对高低温样品的测试和分析表明,高温样品具有单一的物相,而低温样品反应并不完全,是一个混合物.在SrNb2O6光催化活性研究中,常用的甲基橙被选作染料光降解模型,对比试验表明低温样品的光催化活性远高于纯相样品SrNb2O6或Nb2O5.经过讨论和分析,推断出低温产物中存在的异质结（SrNb2O6/Nb2O6）是提高光催化性能的根本原因.     

(Mg1-xSrx)2Al4Si5O18陶瓷的显微结构与微波介电性能研究

采用固相烧结反应法制备(Mg1-xSrx)2Al4Si5O18陶瓷.Sr掺杂促进低温相β-Mg2Al4Si5O18向高温相α-Mg2Al4Si5O18转变,并拓宽了(Mg1-xSrx)2Al4Si5O18陶瓷的致密化烧结温度范围.X射线衍射结果表明在0≤x<0.2范围内,(Mg1-xSrx)2Al4Si5O18陶瓷以(Mg,Sr)2Al4Si5O18堇青石固溶体形式存在;在0.6相似文献   

钛酸锶钡(BaxSr1-xTiO3)陶瓷制备及其介电性能的研究

采用乙酸钡、乙酸锶和钛酸丁酯为原料的溶胶凝胶方法制备了BaxSn1-xTiO3(x=0．6)超细粉体,将BST超细粉体压制成型,进行烧结,得到(Ba0.6Sr004)TiO3陶瓷。通过热分析(DSC／TG)、X射线衍射(XRD)分析(Ba0.6Sr0.4)TiO3粉体合成过程及其相结构变化。采用扫描电子显微镜(SEM)描述(Ba0.6Sr0.4)TiO3烧结体的相结构和显微组织结构变化。阻抗分析仪测量(Ba0.6Sr0.4)TiO3陶瓷的-50～100℃介电温谱。实验结果表明BaxSn1-xTiO3粉体的相结构为立方相钙钛矿结构,其合成温度及烧结温度分别为800℃及1250℃,均低于传统工艺的相应温度。(Ba0.6Sr0.4)TiO3陶瓷在-50～100℃温度范围内,其电容率随着烧结温度升高而增大.介电损耗tgδ在-50～100℃温度范围内,随温度的增加而降低。1250℃的(Ba0.6Sr0.4)TiO3陶瓷烧结体样品存在介电峰弥散化。     

MgO-Fe2O3-Nb2O5混合物中钙钛矿相前驱体的煅烧反应过程研究

用XRD法系统地研究了PFN－PMN二元系中钙钛矿相的前驱体FeNbO4（FN）－MgNb2O6(MN）煅烧过程中的物相变化。发现，富镁的前驱体混合物在较高的煅烧温度下有富镁的Mg4Nb2O9(M4N)生成，而富铁的前驱体混合物中FN的生成，有利于抑制M4N的形成。M4N的形成与钙钛矿相煅烧产物中烧绿石相的出现有密切的关系。在MN与FN二种前驱体中，MN在大约650℃时即开始生成，而FN则需至800℃才开始生成，表明较低温度下Fe2O3的反应尖性不及MgO的反应活性。     

SrO-CeO2体系化合物的固相反应机理研究

以SrCO3和CeO2为原料，采用XRD和TG／DTA分析技术研究了SrO—CeO2体系化合物的物相形成过程．结果发现，当灼烧温度低于950℃时，原始粉料只反应生成Sr2CeO4；而当灼烧温度高于950℃时，在反应的初始阶段，原始粉料中同时出现SrCeO3和Sr2CeO4物相，在950℃附近，主要产物为Sr2CeO4，在1000℃以上，主要产物为SrCeO3，SrCeO3和Sr2CeO4物相分别存在着两种形成机制，当温度高于1000℃时，SrCeO3由SrO和CeO2直接反应生成，而Sr2CeO4则由SrCeO3和SrO反应生成；当温度低于950℃时，Sr2CeO4由SrO和CeO2直接反应生成，而在950℃附近SrCeO3则由Sr2CeO4和CeO2反应生成．依据这些实验结果，给出了SrO—CeO2体系固相反应规律，并对SrCeO3衍射数据JCPDS36-980的错误结果进行了分析．荧光光谱测试结果表明，Sr2CeO4物相的形成机制对其激发光谱产生明显的影响．     

Abnormal grain growth and liquid-phase sintering in Sr0.6Ba0.4Nb2O6 (SBN40) ceramics

Ceramics of Sr0.6Ba0.4Nb2O6 (SBN40) were prepared by the conventional mixed oxide route. Sintering at temperatures 1260 °C led to rapid, non-uniform grain growth and a duplex microstructure. Presintering at 1250 °C followed by higher temperature sintering (1350–1450 °C) controlled grain growth. Rapid cooling from 1450 °C froze-in second phases at grain boundaries. Scanning electron microscopy and transmission electron microscopy showed that the resulting grain-boundary phases were Nb2O5-rich and BaO-deficient, having low liquid-formation temperatures. In contrast, SBN40 ceramics prepared with excess BaO and a deficiency of Nb2O5 showed no enhancement of grain growth at the highest temperature. Sintering behaviour and microstructural development provide evidence for the existence of a liquid phase which assists abnormal grain growth. The effect of presintering in controlling grain growth is discussed, and a mechanism for abnormal grain growth in Sr0.6Ba0.4Nb2O6 (SBN40) ceramics is proposed. © 1998 Chapman & Hall     

The influences of rapid-thermal annealing on the characteristics of Sr0.6Ba0.4Nb2O6 thin film

The Sr0.6Ba0.4Nb2O6 (SBN) thin films were successfully prepared on Pt/Ti/Si and SiO2/Si/Al substrates and crystallized subsequently using rapid thermal annealing (RTA) process in ambient atmosphere for 1 min. The surface morphologies and thicknesses of as-deposited and annealed SBN thin films were characterized by field emission scanning electron microscopy, and the thickness was about 246 nm. As compared with the as-deposited SBN thin films, the RTA-treated process had improved the crystalline structures and also had large influence on the crystalline orientation. When the annealing temperatures increased from 700 degrees C to 900 degrees C, the diffraction intensities of (410) and (001) peaks apparently increased. Annealed at 900 degrees C, the (001) peak had the maximum texture coefficient and SBN thin films showed a highly c-axis (001) orientation. The influences of different RTA-treated temperatures on the polarization-applied electric field (P-E) curves and the capacitance-voltage (C-V) curves were also investigated.     

Low temperature preparation of nanocrystalline Sr0.5Ba0.5Nb2O6 powders using an aqueous organic gel route

Nano-sized Sr_0.5Ba_0.5Nb₂O₆ (SBN50) ceramic powders have been synthesized by an aqueous organic gel route. Homogeneous Sr-Ba-Nb precursor gels are prepared with Ba-EDTA, Sr-EDTA, and Nb-citrate complex as source of Sr, Ba, and Nb, respectively. Citric acid and ethylenediaminetetraacetic acid (EDTA) were used as the chelating agents. The structural variation of the SBN powder with annealing temperature was studied by TG-DTA, FT-IR and XRD. The precursor gel on calcination at 800 °C for 2 h produces a pure tungsten bronze SBN phase and the corresponding average particle size is 30-50 nm. The influences of the pH and the molar ratio of citric acid:Nb cation on the formation of homogeneous Sr-Ba-Nb precursor gels were also studied. The results show that a homogeneous Sr-Ba-Nb precursor gel with no precipitate is formed at pH 8 and the optimum molar ratio of citric acid and the metal cations is 3:1.     

复相陶瓷 BSTN的相组成和微观结构与 Sr/Ba比的关系

按配方(1-x)BaO·xSrO·0．7TiO2·0．3Nb2O5制备不同Sr／Ba比的钙钛矿／钨青铜复相陶瓷,用XRD和SEM研究其组成和结构与Sr／Ba比的关系．结果表明,改变Sr／Ba比对两相稳定共存没有影响;受同一体系中两相不同固溶能力控制,钙钛矿相中Ba2+和Sr2+之间的置换几率远大于钨青铜相中,其Sr／Ba比随体系Sr／Ba比变化,而钨青铜相的Sr／Ba比维持约0．667基本不变;控制体系Sr／Ba比偏离该值,钙钛矿相的晶格常数相应偏离标准值,而钨青铜相基本不变;提高Sr／Ba比,钙钛矿相晶粒尺寸减小,而钨青铜相变化不明显．两相共存体系中,当两相都可形成固溶体但固溶能力不同时,固溶度大的一相优先参与置换,并抑制另一相的固溶．     

SnO2掺杂对BMN陶瓷结构及介电性能的影响

采用固相烧结法制备Ba(Mg_(1/3)Nb_(2/3))O_3+x(x=0~8)%SnO_2(BMSN,x为质量分数)微波介质陶瓷,并研究SnO_2掺杂对Ba(Mg_(1/3)Nb_(2/3))O_3(BMN)微波介质陶瓷结构及介电性能的影响。XRD分析表明,陶瓷体系中存在两种相,主晶相Ba(Mg_(1/3)-Nb_(2/3))O_3和附加相Ba_5Nb_4O_(15)。随着x的增大,BMSN陶瓷体系的相结构逐渐由钙钛矿六方结构转变为立方结构,同时有序相逐渐由1∶2有序结构转变为1∶1有序结构。研究表明:添加适量的SnO_2可以促进液相烧结,当SnO_2掺杂质量分数为6%时,BMN陶瓷致密化烧结温度由纯相时的1 550℃以上降低至1 200℃,表观密度ρ=6.39g/cm3,相对理论密度为99.1%,此时BMSN陶瓷体系拥有优良的微波介电性能——高相对介电常数(ε_r=33.6),接近于零的谐振频率温度系数(τ_f=0.15×10~(-6)℃~(-1)),高品质因数与谐振频率的乘积(Q·f=112 300GHz(8GHz))。     

Formation of the fluorite phase and other related phases in the system Y2O3–Ta2O5–MO (M−Mg, Ca, Sr or Ba)

The formation of the fluorite phase Y0.8Ta0.2O1.7 and other related phases in the system Y2O3–Ta2O5–MO (M=Mg, Ca, Sr or Ba) has been studied. The single fluorite phase formed when up to 12 mol% MgO was added to the fluorite phase; however, MgO appeared as the second phase as well as the main fluorite phase when more than 16 mol% MgO was added. When more than 8 mol% CaO was added to Y0.8Ta0.2O1.7, Ca2YTaO6 and Y2O3 were produced as the second phases as well as the main fluorite phase. Ba2YTaO6 and Sr2YTaO6 of the perovskite-type ordered structure and Y2O3 were produced as well as the main fluorite phase when only 4 mol% BaO or SrO were added to Y0.8Ta0.2O17. The region of the fluorite single phase was found in the system Y2O3–Ta2O5–CaO. The formation of the fluorite phase is assumed to be related to the cation radius of the doped alkaline-earth oxide. © 1998 Chapman & Hall     

BST/BZT/BST多层薄膜结构与性能研究

利用脉冲激光沉积法在LaNiO3/LaAlO3(001)基片上生长了Ba0.6Sr0.4TiO3(BST)和Ba(Zr0.2Ti0.8)O3(BZT)单层薄膜,以及Ba(Zr0.2Ti0.8)O3/Ba0.6Sr0.4TiO3/Ba(Zr0.2Ti0.8)O3(BZT/BST/BZT)多层薄膜.X射线衍射(XRD)分析发现,BST、BZT和LNO薄膜都具有高度的(00l)取向.原子力显微镜(AFM)显示三种样品表面光滑无裂纹,晶粒尺寸和表面粗糙度相当.电容测试表明,相对BST、BZT单层薄膜,多层薄膜具有最大的品质因数42.07.表明多层薄膜在微波应用中具有很大的潜力.     

半化学法制备0.80Pb(Mg1/3Nb2/3)O3-0.20PbTiO3陶瓷的反应机理

采用半化学法制备了纯钙钛矿相的0．80Pb（Mg1/3Nb2/3）O3－0．20PbTiO3（简称为0．80PMN－0．20PT）陶瓷。反应前驱体是以硝酸镁的饱和溶液代替传统氧化物混合法中的氧化镁，与PbO、Nb2O5和TiO2混合球磨得到的。该前驱体的TG－DTG－DSC和XRD分析表明，半化学法的反应机理不同于传统氧化物混合法和二次合成法的反应机理。在煅烧过程中，硝酸镁与氧化铅反应生成铅的活化中间体Pb6O5（NO3）2，由此活化的PbO或Pb3O4可与Nb2O5生成不稳定的、缺B位的焦绿石相Pb3Nb2O8，再与MgO反应生成钙钛矿相PMN－PT。     

Nanocrystallization of SrBi2Nb2O9 from glasses in the system Li2B4O7---SrO---Bi2O3---Nb2O5

Transparent glasses in the system (100−x)Li₂B₄O₇–x(SrO---Bi₂O₃---Nb₂O₅) (10≤x≤60) (in molar ratio) were fabricated by a conventional melt-quenching technique. Amorphous and glassy characteristics of the as-quenched samples were established via X-ray powder diffraction (XRD) and differential thermal analyses (DTA) respectively. Glass–ceramics embedded with strontium bismuth niobate, SrBi₂Nb₂O₉ (SBN) nanocrystals were produced by heat-treating the as-quenched glasses at temperatures higher than 500 °C. Perovskite SBN phase formation through an intermediate fluorite phase in the glass matrix was confirmed by XRD and transmission electron microscopy (TEM). Infrared and Raman spectroscopic studies corroborate the observation of fluorite phase formation. The dielectric constant (_r) and the loss factor (D) for the lithium borate, Li₂B₄O₇ (LBO) glass comprising randomly oriented SBN nanocrystals were determined and compared with those predicted based on the various dielectric mixture rule formalism. The dielectric constant was found to increase with increasing SBN content in LBO glass matrix.