共查询到17条相似文献,搜索用时 78 毫秒
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测量了碱土金属正磷酸盐Ba3(PO4)2和Sr3(PO4)2常温及高温拉曼光谱, 对拉曼振动模式进行指认, 并分析了晶体拉曼振动光谱及晶体结构在高温下的变化. 在温度升高的过程中, 拉曼振动频率向低频移动且振动峰宽度展宽, 晶体中的P-O平均键长随温度升高而变长, 但O-P-O的键角并未发生变化. 晶体在900 ℃以下无结构相变发生.
关键词:
3(PO4)2和Sr3(PO4)2')" href="#">Ba3(PO4)2和Sr3(PO4)2
高温拉曼光谱
振动模式
高温结构 相似文献
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利用高温固相反应法制备了Eu3+掺杂的Sr2CeO4样品,并对其吸附水前后的光谱特性进行了研究.结果发现,对于刚制备的Sr2-xEuxCeO4+x/2样品, 在Ce4+—O2-的电荷迁移激发中,只有强激发带(~35700cm-1)与Eu3+离子间存在能量传递,而弱激发带 (~29400cm-1)只是引起Ce4+—O2-的电荷迁移发射;在Sr2-xEuxCeO4+x/2样品吸附水后,Eu3+的线状吸收跃迁强度显著增加, Ce4+—O2-两个激发带均向Eu3+离子传递能量. Ce4+—O2-强激发带通过交换作用向Eu3+离子传递能量,而弱激发带与Eu3+离子间的能量传递机理是非辐射多极子近场力的相互作用.
关键词:
2-xEuxCeO4+x/2')" href="#">Sr2-xEuxCeO4+x/2
发光性质
能量传递
吸附水 相似文献
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MgO对Sr2SiO4:Eu2+荧光粉发光性质的影响 总被引:1,自引:1,他引:0
通过在Sr2SiO4:Eu2+荧光粉中加入MgO,提高了Sr2SiO4:Eu2+荧光粉的蓝光和黄光发射带的发射强度,研究了MgO浓度对Sr2SiO4:Eu2+荧光粉发光强度的影响。当Mg与Si的量比在1.0附近时,荧光粉的亮度较高,且发光颜色为白色。通过调节Sr2SiO4:yEu2+ ,MgO荧光粉中Eu2+的掺杂浓度,可以调节荧光粉的发光颜色。用Sr2SiO4:Eu2+ ,MgO和400 nm的InGaN管芯制备的白光LED,色坐标优于α'-Sr2SiO4:Eu2+和β-Sr2SiO4:Eu2+荧光粉制成的白光LED,显色指数和流明效率高于β-Sr2SiO4:Eu2+和α'-Sr2SiO4:Eu2+制成的白光LED。 相似文献
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以MCM-41为硅源,采用共沉淀法制备Sr2-xSiO4:xCe3+(x=0.01~0.09,步长为0.01)和Sr1.95-ySiO4: 0.05Ce3+,yLi+(y= 0.01~0.07,步长为0.02)蓝紫色荧光粉。Sr2-xSiO4:xCe3+的发射光谱是一个不对称的宽带,最大峰值在410 nm左右。Ce3+的最佳掺杂量为5%。Ce3+离子倾向于占据九配位的Sr(Ⅱ)格位。共掺电荷补偿剂Li+可以有效地提高Sr1.95SiO4: 0.05Ce3+的发光强度,其中Li+离子对1 100 ℃煅烧样品的发光强度的提高程度比1 000 ℃的更高,Li+的最佳掺杂量为y=0.05。 相似文献
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采用高温固相法制备一系列Sr2SiO4∶Eu0.01, Dyx(x=0.000 1, 0.002 5, 0.005, 0.01)应力发光材料,研究了不同掺杂浓度下,Sr2SiO4∶Eu, Dy的光致发光和应力发光性质。研究结果表明在掺杂Dy3+浓度较低时,样品同时存在α和β两种相,当掺杂Dy3+浓度增加时,则出现β到α的相转变。由于Eu2+占据Sr2+格位的不同,样品在蓝光区486 nm(Sr1)和绿光区530 nm(Sr2)有两个峰存在。而应力发光光谱与余辉光谱类似,均只呈现出530 nm的发光,这说明二者的发光来源于占据Sr2格位的Eu2+,都是通过改变陷阱的浓度实现发光性能的变化,但Sr2SiO4∶Eu, Dy的应力发光强度的变化还与其结构改变有关。同时,Sr2SiO4∶Eu, Dy应力发光强度与所施加的力之间呈良好的线性关系,并且可用眼睛观察到明显的黄色应力发光,这为应力发光传感器准确检测物体所受应力提供依据。结合余辉、热释以及应力发光性质,推测Sr2SiO4∶Eu, Dy的应力发光机制应是压电产生的电致发光。 相似文献
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采用溶胶-凝胶法,在氧气氛中和层层晶化的工艺条件下,成功地制备了沉积在Pt/Ti/SiO2/Si(100)衬底上的铁电性能优良的Sr2Bi4Ti5O18 (SBTi)薄膜,并研究了SBTi薄膜的微结构、表面形貌、铁电性能和疲劳特性.研究表明:薄膜具有单一的层状钙钛矿结构,且为随机取向;薄膜表面光滑,无裂纹,厚度约为725nm;铁电性能测试显示较饱和、方形的电滞回线,当外电场强度为275kV/cm时
关键词:
溶胶-凝胶法
铁电薄膜
2Bi4Ti5O18')" href="#">Sr2Bi4Ti5O18 相似文献
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用传统固相烧结法制备了Sr2Bi4-xDyxTi5 O18(SBDT-x, x=0—0.20)陶瓷样品. x射线衍射分析表明, 微量的Dy掺杂没有影 响Sr2Bi4Ti5O18(SBTi) 原有的层状钙钛 矿结构. 通过研究样品的介电特性, 发现Dy掺杂减小了材料的损耗因子, 降低了样品铁电- 顺电相转变的居里温度. 铁电性能测量结果表明, 随Dy含量的增加, SBDT-x系列样品的剩余 极化先增大, 后减小. 当Dy掺杂量为0.01时, 剩余极化达到最大值, 约为20.1 μC·cm-2. 掺杂引起剩余极化的变化, 与材料中缺陷浓度、内应力以及晶格畸变程度等因 素有关, 是多种作用机理相互竞争的结果. (Bi2O2)2+ 层通常被看作是绝缘层和空间电荷库, 对材料的铁电性能起关键作用. 掺杂离子进入(Bi2O2)2+层会导致铁电性能变差.
关键词:
2Bi4Ti5O18陶瓷')" href="#">Sr2Bi4Ti5O18陶瓷
Dy掺 杂
铁电性能
居里温度 相似文献
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Niina Jalarvo Camilla Haavik Camilla Kongshaug Poul Norby Truls Norby 《Solid State Ionics》2009,180(20-22):1151-1156
The hydrated oxygen deficient complex perovskite-related materials Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O were studied at high water vapour pressures over a large temperature range by electrical conductivity measurements, thermogravimetry (TG), and X-ray powder diffraction (XRPD). In humid atmospheres both materials are known to exhibit protonic conductivity below dehydration temperatures, with peak-shaped maxima at about 500 °C. In this work we show that the peaks expand to plateaus of high conductivity from 500 to 700 °C at a water vapour pressure of 1 atm. However, in situ synchrotron XRPD of Sr4(Sr2Nb2)O11·nH2O as a function of temperature shows that these observations are in fact coincident with melting and dehydration of a secondary phase Sr(OH)2. The stability of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O in humid atmospheres is thus insufficient, causing decomposition into perovskites with lower Sr content and SrO/Sr(OH)2 secondary phases. This, in turn, rationalizes the observation of peaks and plateaus in the conductivity of these materials. 相似文献
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利用高温固相反应法分别合成了不同物相形成机理的Sr2CeO4,Sr 2CeO4∶Ca 2+和Sr2CeO4∶Ba2+样品,并对其光谱特性进行 了研究.结果发现,对于由SrO和CeO2直接反应生成的Sr2CeO4(Ⅰ),激发主峰位于256nm 左右;而对于SrCeO3和SrO反应生成的Sr2CeO4(Ⅱ),激发主峰位于279nm左右.在Sr2CeO4(Ⅰ)中掺入Ca2+,其激发光谱随着Ca2+离子浓度的增加逐渐接近于Sr2CeO4 sub>(Ⅱ)的激发光谱.激发主峰带应属于CeO6八面体终端Ce4+—O2-键的电荷迁移 带.对于激发光谱中340nm左右的弱激发峰,其峰值波长不受形成机理及Ca2+掺杂的影响,只是其强度 随着 激发主峰的红移而增加,它可能属于CeO6八面体平面上Ce4+—O2-键的电荷 迁移带.形成机理及Ca2+掺杂对发射光谱没有影响.Ca2+在Sr 2CeO 4(Ⅱ)与Ba2+在Sr2CeO4(Ⅰ)和(Ⅱ)中均难 于替代Sr2+的位置. 相似文献
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This work presents the influence of europium dopant on optical properties of Sr2SnO4:Eu3+ powders fabricated by a facile low temperature method. Powders were obtained from the same amounts of Eu3+ doping into the different concentrations of Sr(NO3)2. Powders were examined by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). SEM measurements different Eu concentrations in fabricated powders was determined to found different morphologies. XRD analysis revealed the existence of crystalline Sr2SnO4 in the form of tetragonal and the diffraction intensity was remarkably changed. PL studies showed a red luminescence of Sr2SnO4:Eu3+ powders. The intensity of luminescence increased with better crystallinity. This approach provides economically viable route for large-scale synthesis of this kind of nanopowders. 相似文献
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Electronic structure and optical properties of Nb-doped Sr2TiO4 by density function theory calculation 下载免费PDF全文
This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional theory(DFT).The calculated results reveal that due to the electron doping,the Fermi level shifts into conduction bands(CBs) for Sr2 Nb x Ti1 x O4 with x=0.125 and the system shows n-type degenerate semiconductor features.Sr2TiO4 exhibits optical anisotropy in its main crystal axes,and the c-axis shows the most suitable crystal growth direction for obtaining a wide transparent region.The optical transmittance is higher than 90% in the visible range for Sr2 Nb 0.125Ti0.875O4. 相似文献
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A blue-white emitting Sr2CeO4 phosphor was synthesized via a simple sol-gel poly vinyl alcohol (PVA)-complexing process using strontium nitrate and cerium nitrate as raw materials. The samples were characterized by TG/DTA, XRD, FTIR, SEM and photoluminescence spectroscopy. The X-ray diffraction study confirms the structure of the system to be orthorhombic. The emission spectra when excited at 267 nm peaks at ∼470 nm. The emission band is assigned to the energy transfer between the molecular orbital of the ligand and charge transfer state of the Ce4+ ion. The Commission International de l'Eclairage (CIE) co-ordinates for the Sr2CeO4 sample were also calculated. 相似文献
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In this paper we report the combustion synthesis of trivalent rare-earth (RE3+ = Dy, Eu and Ce) activated Sr4Al2O7 phosphor. The prepared phosphors were characterized by the X-ray powder diffraction (XRD) and photoluminescence (PL) techniques. Photoluminescence emission peaks of Sr4Al2O7:Dy3+ phosphor at 474 nm and 578 nm in the blue and yellow region of the spectrum. The prepared Eu3+ doped phosphors were excited by 395 nm then we found that the characteristics emission of europium ions at 615 nm (5D0?7F2) and 592 nm (5D0?7F1). Photoluminescence (PL) peaks situated at wavelengths of 363 and 378 nm in the UV region under excitation at around 326 nm in the Sr4Al2O7:Ce3+ phosphor. 相似文献
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Enhancement of photoluminescence in Sr2CeO4 phosphors by doping with non-rare earth impurities 下载免费PDF全文
Non-rare earth impurity doped Sr 2 CeO 4:X (X=Zn,Hg,Al,Ag,Cr) phosphors are prepared by using the combustion method.The structural and photoluminescent properties of the as-prepared phosphors are investigated by X-ray diffraction (XRD) and photoluminescence at room temperature.Experimental results show that zinc addition and firing processing can effectively enhance the photoluminescence of Sr 2 CeO 4 phosphors. 相似文献