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1.
BSO晶体的高温拉曼光谱与高温结构特征   总被引:4,自引:0,他引:4  
阐述了BSO晶体在常温下的结构特征,通过测量晶体在常温下的拉曼光谱,对晶格主要振动模式进行了指认,测量晶体升温至熔化过程中不同温度下的拉曼光谱,分析研究了其微观结构在升温过程中的变化以及在高温状态下的结构特征。  相似文献   

2.
本文采用拉曼散射技术在温度从374到-196℃的范围内,研究了弛豫型铁电单晶0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3(PMNT)。观察了在不同温度下拉曼光谱的变化,经分析这些变化反映了该晶体经历了两个相变:第一个相变温度发生在120℃,从顺电立方相到铁电四方相的相变,780 cm-1处模式在VH偏振下的改变标志了这一相变;第二个相变温度发生在34℃,是从铁电四方相到铁电三方相的相变,软模的出现代表了这一相变。  相似文献   

3.
采用固相烧结法制备了六方晶型结构的MgTiO3粉体. 经高温原位X射线衍射分析(293-1473 K)进行了表征与确认,获得了晶胞参数及其随温度的变化,测量了高温原位拉曼光谱(273-1623 K),并运用第一性原理理论计算方法对应核实了拉曼谱峰的归属. 结果表明,随着温度升高,MgTiO3晶面间距和晶格常数增大,从而反映对于拉曼光谱较为敏感的键长和键角的变化;温致拉曼位移可以反映Ti-O,Mg-O等键长以及Ti-O-Ti,Ti-O-Mg与Mg-O-Mg等键角随温度的细微变化,相关关系则独立于温度,有效提升了原位拉曼光谱微探针诊断技术的分析能力;拉曼谱峰随温度升高而展宽,表明原子瞬间运动振幅加剧,弥散性增加,稳定性有所下降,但仍维持六方晶型. 关键词: 3')" href="#">MgTiO3 微结构 拉曼光谱 高温  相似文献   

4.
本文采用拉曼光谱研究不同配比的二元钠硅酸盐玻璃,结果显示碱金属阳离子的浓度影响结构中桥氧的含量,且不同初级结构Qi具有不同的特征峰。对Na2O·3SiO2玻璃进行高温拉曼和核磁共振研究,分别采用精细结构Qjklmi(m1h,m2q,m3t)和Qjklmi取代初级结构Qi进行解谱拟合和结构分析得到得到初级微结构单元的实际分布,结合量化分析结果计算其拉曼散射截面,定量分析Na2O·3SiO2玻璃及熔体在升温状态下结构随温度的变化。从室温到到熔态,Qi结构之间存在动态平衡,Na2O·3SiO2玻璃随着温度的升高从玻璃态到高弹态,最后经历粘流态到熔态。  相似文献   

5.
紫外拉曼光谱研究钇掺杂的氧化锆体系表面相变   总被引:4,自引:1,他引:3  
本文用紫外拉曼 ,近可见拉曼光谱和XRD检测了不同焙烧温度下Y2 O3-ZrO2 的相变过程。紫外拉曼光谱对样品表面相变极其灵敏 ,而近可见拉曼光谱和XRD提供的主要是体相和表面的混合信息。在紫外拉曼谱图中 ,只观察到单斜相的谱峰 ,没有明显的四方晶相的信号 ,这表明样品的表面主要是单斜晶相。然而 ,XRD和近可见拉曼光谱的结果显示Y2 O3-ZrO2 体相是四方晶相。焙烧温度超过 40 0°时 ,紫外拉曼 ,近可见拉曼和XRD晶之间明显不同的结果表明Y2 O3-ZrO2 在表面区四方相很易转变为单斜相 ,体相中的四方相由于钇的添加而稳定存在。根据紫外拉曼和XRD结果 ,当升高温度时 ,在样品的表面形成一单斜相层 ,体相钇稳定的四方相 ,且由于Y2 O3的存在抑制了单斜相进一步向体相发展。  相似文献   

6.
采用高温固相法制备了Eu3+掺杂的层状钙钛矿M2TiO4∶Eu3+(M=Ca,Sr,Ba)红色荧光粉,借助X射线衍射、紫外可见漫反射光谱和荧光光谱研究了不同煅烧温度下粉体的晶相组成及其光致发光性能。结果表明:在煅烧温度1 000℃保温2h时即可得到纯相Sr2TiO4和Ba2TiO4粉体,但即使进一步的升高温度并延长保温时间均无法得到Ca2TiO4粉体。Ba2TiO4∶Eu3+粉体在395nm激发下发射594nm(5 D0→7 F1)和615nm(5 D0→7 F2)橙红光。Sr2TiO4∶Eu3+粉体区别于通常Eu3+的特征发射,在近紫外和蓝光激发下主要发射578nm(5 D0→7 F0)和626nm(5 D0→7 F2)的强烈橙/红光,具有更好的红光色纯度和发光强度,其中363nm电荷迁移激发下具有最高的发光效率,是一种适用于近紫外和蓝光LED芯片的红光材料。  相似文献   

7.
炸药晶体的相结构、相变过程以及相变引起的微结构变化对炸药性能有重要影响。为研究HMX晶体的高温相变及其引起的裂纹对点火的影响,开展了HMX晶体的原位高温拉曼光谱、X射线衍射实验以及落锤实验。通过拉曼光谱和X射线衍射谱识别出不同温度加载和后处理方法对HMX晶体相结构和微结构的影响。制备了3类含有不同相结构和裂纹的HMX样品,实现了相结构和裂纹对点火影响的解耦。落锤实验结果显示,对于3类HMX晶体,按照敏感度由高到低排序依次为含裂纹的β-δ混相、含裂纹的β相、无裂纹的β相。最后,分析了高温相变和裂纹提高HMX晶体感度的原因。  相似文献   

8.
采用有机金属沉积法(MOD)制备了Bi4Ti3O12(BIT)和Bi3.25La0.75Ti3O12(BLT)前驱体溶液,分别在单晶硅基片上制备了BIT和BLT铁电薄膜.前驱体溶液的干凝胶粉体和铁电薄膜分别用红外光谱(FTIR)、拉曼光谱和环境扫描电镜(ESEM)进行了表征.结果表明600℃时晶粒实现了由焦绿石相向类钙钛矿相结构的完全转变;温度升高,晶粒尺寸增大,薄膜结晶效果得到改善;引入镧使Ti-O和Bi-O键吸收峰位置向低波数频移,高温时频移率较大;500℃热处理时,干凝胶中乙二醇甲醚、乙酰丙酮完全分解,温度超过600℃后,残留的水及硝酸根离子挥发或分解.  相似文献   

9.
《光散射学报》2005,17(4):418-430
第1期不同退火温度的ZrO2纳米颗粒光学声子和表面吸附分子的拉曼散射研究…………………………………………………………………………………刘玉龙,丁硕,朱恪,萧季驹(1)纳米PbTiO3温致相变的原位高温拉曼光谱研究………………………………………………………………………………  相似文献   

10.
采用铜蒸气脉冲激光光源和时间分辨探测技术,测定了CaSiO3晶体及其熔融态的常温及高温拉曼光谱(在298~2000K的温度范围),观察了其在高温下的相转变、升温过程及其熔体的特征光谱变化。通过谱图解析,研究分析了熔体微结构单元硅氧四面体Qn(n为单个硅氧四面体的桥氧数)分布、聚合状况及其与固态晶体的区别  相似文献   

11.
The phase transformation from the pyrochlore phase into the perovskite phase in ferroelectric films of lead zirconate titanate on silicon substrates due to annealing of samples has been investigated experimentally and theoretically. It has been proved that this transformation is a typical first-order phase transition, which is accompanied by a change in the density of the phases and the release of the latent heat of the phase transition. The quantitative evaluations have demonstrated that the difference in the densities of two phases, namely, the perovskite phase and the original parent pyrochlore phase, leads to the generation of elastic stresses in the original parent phase. In turn, these stresses bring about the nucleation of micropores in the bulk of the lead zirconate titanate film. The thermodynamic conditions providing the formation of micropores have been established and the critical size of the micropores has been calculated. A characteristic relationship between the critical size of nuclei of the perovskite phase and the radius of micropores at which the perovskite phase is separated from the parent pyrochlore phase has been derived. This relationship has been verified experimentally. The sizes of the micropores have been determined using scanning electron microscopy, and the changes in the phase composition during the phase transformation have been found using an electron probe X-ray microanalysis. It has been demonstrated theoretically and experimentally that the relaxation of elastic stresses in the lead zirconate titanate thin films during the phase transition occurs through the nucleation and growth of micropores at the interface between the new and parent phases.  相似文献   

12.
The Raman studies of lead zirconate titanate with varied grain size from 27.5 nm to 983 nm were performed under pressure up to 32 GPa to elucidate the scenario of phase transition pressures of lead zirconate titanate, which lies in the morphotropic phase boundary. The coexistence of ferroelectric rhombohedral and tetragonal phases at ambient condition changed to the coexistence of tetragonal and cubic phases at intermediate pressure and finally, transited to paraelectric cubic phase at elevated pressure. The pressure evolution of Raman spectra results indicated that the phase transition pressure increased with the reduction of the particle size.  相似文献   

13.
傅宏刚  赵冰 《光散射学报》1999,11(2):127-131
本文测定了不同粒径的钛酸铅纳米晶的FT Raman光谱,确定了各光学声子模的归属,发现A1(1TO)声子峰的多重劈裂特征,支持了Foster等人的非谐性振动模型。粒径和温度的变化将使声子频率发生位移并带来峰宽的变化,A1(TO)模比对应的E(TO)模频移速度快,当由铁电相到达居里点时,二者将在某一较低频率处汇合。  相似文献   

14.
We report here the formation of single phase lead zirconate titanate (PZT) nanopowder with composition Pb(Zr0.52Ti0.48)O3 and average crystallite size 12?C20?nm, synthesized by sol?Cgel process. The phase evolution of PZT gel powder, heat treated at temperatures 550, 650 and 800°C was monitored by X-ray diffraction (XRD) and X-ray photo-electron spectroscopy (XPS). The high resolution XPS spectra of Pb4f, Zr3d, Ti2p and O1s show that PZT with pure perovskite structure is obtained at 800°C while at lower temperatures pyrochlore phase co-exists with perovskite phase. The XRD results also support this analysis. We have also identified the pyrochlore phase using XPS by analyzing the corresponding variations in the FWHM values, peak positions and the separation between the spin doublets of Pb, Zr and Ti associated with it. The composition of the final powder obtained with pure perovskite structure is calculated and is close to the designed value.  相似文献   

15.
Lead Titanate (FT) materials were prepared by a sol-gel process in an air atmosphere using lead acetate and titanium propoxide in methoxyethanol as the precursor materials. FTIR and Raman spectroscopy were used to characterize the various structural changes that occurred during various stages of the preparation. A new crystalline lead titanate phase was detected by both Raman spectral and X-ray diffraction techniques when heating the gelled material at 430°C. In-situ Raman spectra were measured at high temperatures for the resulting sol-gel prepared PT material to investigate its phase-transition and soft-mode behavior.  相似文献   

16.
In terms of a semiphenomenological exchange charge model, we have obtained estimates of parameters of the crystal field and parameters of the electron-deformation interaction in terbium titanate Tb2Ti2O7 with a pyrochlore structure. The obtained set of parameters has been refined based on the analysis of spectra of neutron inelastic scattering and Raman light scattering, field dependences of the forced magnetostriction, and temperature dependences of elastic constants.  相似文献   

17.
Physics of the Solid State - Features of the microstructure and piezoelectric response of perovskite islands in a pyrochlore phase matrix in lead zirconate titanate thin films prepeared by the...  相似文献   

18.
Various glass samples were prepared by melt quench technique in the glass system [(Ba1? x Sr x ) TiO3]–[2SiO2–B2O3]–[K2O] doped with 1?mole% of La2O3. Infrared spectra show the number of absorption peaks with different spliting in the wave number range from 450 to 4000?cm?1. Absorption peaks occurs due to asymetric vibrational streching of borate by relaxation of the bond B–O of trigonal BO3. Raman spectra show the Raman bands due to ring-type metaborate anions, symmetric breathing vibrations BO3 triangles replaced by BO4 tetrahedra, and symmetric breathing vibrations of six-member rings. The differential thermal analysis of a glass sample corresponding to composition x?=?0.0 shows crystallization temperature at 847°C and glass transition temperature at 688°C. X-ray diffraction (XRD) pattern of glass ceramic samples shows the major crystalline phase of BaTiO3 whereas pyrochlore phases of barium titanium silicate. Scanning electron micrographs confirm the results of XRD as barium titanate is major crystalline phase along with pyrochlore phase of barium titanium silicate.  相似文献   

19.
The parameters of mechanochemical synthesis of barium titanate nanoparticles from barium titanyl oxalate and an oxide mixture are optimized. X-ray phase analysis, infrared and Raman scattering spectroscopy, differential scanning calorimetry, and dielectric spectroscopy are applied to demonstrate that the nanoparticles contain the cubic and tetragonal crystal lattice modifications. The impurity spectra for the particles obtained by the mechanochemical method from different initial substances are identical. The ferroelectric phase volume increases as hydroxyl groups are annealed from the crystal lattice and decreases upon annealing of metal atom vacancies.  相似文献   

20.
Thin films of lead zirconate titanate (PZT) were obtained by a modified sol–gel route on float glass and indium tin oxide (ITO)-covered float glass substrates. Different thermal treatments were performed on the deposited films in the temperature range 100–700°C. Spectroscopic ellipsometry was used to investigate the optical properties of the deposited films, and the changing optical absorption spectra were interpreted in terms of the growth of two different crystal phases, pyrochlore and ferroelectric perovskite, as a function of annealing temperature. Moreover, a specific resonance at 1.9 nm was detected when thin PZT films are deposited on ITO substrates and was attributed to a particular charge distribution at the interface. Finally, the performance in rectifying the electro-optical response of asymmetric nematic liquid crystal cells was tested for some of the films undergoing different thermal treatments.  相似文献   

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