MC与$lt;i$gt;M$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;+1$lt;/sub$gt;$lt;i$gt;AC$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;$lt;/sub$gt;稳定性与电子特征的第一性原理研究

研究MC与M_n+1AC_n(M=Sc, Ti, V, Cr, Mn; A=Al, Si, P, S; n=1, 2, 3)结构的稳定性与电子特征有利于探究三元层状结构M_n+1AC_n稳定性的内在原因和设计新型M_n+1AC_n结构. 第一性原理计算研究表明, M-3d与C-2p轨道间的电子转移对MC与M_n+1AC_n 的形成焓有较大影响. 供电子能力较强的前过渡金属可以形成稳定的MC结构. 计算结果显示, MC结构是缺电子体系, 其趋向于与具有一定供电子能力的MA结构结合形成M_n+1AC_n. 与M₂PC和M₂SC 相比, M₂AlC和M₂SiC可以更为容易地被分离成二维 M₂C结构. 关键词： MAX相结构 第一性原理 电子结构 过渡金属碳化物     

Ca$lt;sub$gt;2$lt;/sub$gt;Si（O$lt;sub$gt;4-$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;N$lt;sub$gt;$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;）：Eu$lt;sup$gt;2+$lt;/sup$gt;绿色荧光粉的制备及其发光性能

利用在Ca-Si-O干凝胶前驱体中添加Si₃N₄的方法于非还原气氛下合成了含N固溶体Ca₂Si（O_4-xN_x）：Eu²⁺绿色荧光粉. 通过X射线衍射仪、扫描电子显微镜以及荧光分光光度计分别分析了产物的物相结构、颗粒形貌和发光性能. 结果显示,Si₃N₄与前驱体的混合物在非还原气氛（纯氮气）下于1100℃焙烧后获得含N固溶体Ca₂Si（O_4-xN_x）：Eu²⁺荧光粉,特别是其中Eu³⁺被还原为Eu²⁺,产物的晶体结构与βup -Ca₂SiO₄相一致. Ca₂Si（O_4-xN_x）：Eu²⁺能够被270–400 nm 范围内的紫外线有效激发,其发射光谱呈宽带发射. 随着N含量的增加,发射峰出现一定程度红移（501–504 nm）,而且发光强度显著提高. 当Eu²⁺浓度为0.25 mol%时发光强度达最大值,浓度超过0.25 mol%时,发光强度显著降低,出现浓度猝灭 效应. 关键词： 白光LED 荧光粉 溶胶凝胶法 3N₄')" href="#">Si₃N₄     

Tb$lt;sub$gt;0.3$lt;/sub$gt;Dy$lt;sub$gt;0.6$lt;/sub$gt;Pr$lt;sub$gt;0.1$lt;/sub$gt;(Fe$lt;sub$gt;1-$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;Al$lt;sub$gt;$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;)$lt;sub$gt;1.95$lt;/sub$gt;合金的磁性、磁致伸缩和穆斯堡尔谱研究

系统研究了室温下Tb_0.3Dy_0.6Pr_0.1（Fe_1-xAl_x）_1.95 （x=0.05,0.1,0.15,0.2,0.25,0.3）合金中元素Al替代Fe对结构、磁性、磁致伸缩性能和自旋重取向的影响.测量结果发现,x<0.2时Tb_0.3Dy_0.6Pr_0.1（Fe_1-xAl_x）_1.95合金基本上是纯的单相,x=0.2时出现其他杂相,杂相随Al替代量的增加不断增多.随Al替代量x的增加,点阵常数a接近于线性增大,Curie温度T_C逐渐下降,而矫顽力H_c急剧下降.振动样品磁强计（VSM）测量发现,磁化强度M随Al替代量x的变化较为复杂.VSM计和磁致伸缩效应测量共同表明,少量Al的替代有利于降低磁晶各向异性,而且随着Al替代量x的增多磁致伸缩系数快速减小,x>0.15时巨磁致伸缩效应消失.穆斯堡尔效应研究发现,随Al含量的增加Tb_0.3Dy_0.6Pr_0.1（Fe_1-xAl_x）_1.95合金中易磁化轴可能在{110}面逐渐偏离了立方晶体的主对称轴,发生自旋重取向,从而引起合金宏观磁性、磁致伸缩性能的变化. 关键词： 磁致伸缩 立方Laves相 自旋重取向 穆斯堡尔谱     

P掺杂对绿色荧光粉BaMgAl$lt;sub$gt;10$lt;/sub$gt;O$lt;sub$gt;17$lt;/sub$gt;:Mn$lt;sup$gt;2+$lt;/sup$gt;性能的影响

采用高温固相法合成P掺杂的BaMgAl₁₀O₁₇:Mn²⁺荧光粉,其中P通过（NH₄）₂HPO₄引入.利用X射线衍射谱、傅里叶变换红外光谱、扫描电子显微镜、能量色散谱、真空紫外光谱等研究了P掺杂对BaMgAl₁₀O₁₇:Mn²⁺晶体结构、微观形貌、发光性能等的影响.研究结果表明：（NH₄）₂HPO₄具有助熔剂的作用,它的加入有助于荧光粉的晶化,改善荧光粉的形貌.P掺杂进入晶格,使得晶胞参数变小,从而改变了Mn²⁺的晶体场环境,引起发射光谱蓝移,色坐标x值降低.P掺杂能有效提高基质对真空紫外线的吸收,从而提高真空紫外激发下的发光强度. 关键词： P掺杂 10O₁₇:Mn²⁺')" href="#">BaMgAl₁₀O₁₇:Mn²⁺ 晶体结构 真空紫外     

用耦合簇理论及相关一致五重基研究SiH$lt;sub$gt;2$lt;/sub$gt;($lt;i$gt;X$lt;/i$gt;$lt;sup$gt;1$lt;/sup$gt;$lt;i$gt;A$lt;/i$gt;$lt;sub$gt;1$lt;/sub$gt;)自由基的解析势能函数

运用单双迭代三重激发耦合簇理论和相关一致五重基对SiH₂的基态结构进行了优化, 并在优化结构的基础上进行了离解能和振动频率的计算. 结果表明: SiH₂的基态为C_2v结构, 平衡核间距R_Si—H= 0.15163 nm, H—Si—H键的键角α=92.363°, 离解能D_e（HSi—H）=3.2735 eV, 频率ν₁（a₁）=1020.0095 cm^-1, ν₂（a₁）=2074.8742 cm^-1, ν₃（a₁）=2076.4762 cm^-1. 这些结果与实验值均较为相符. 对H₂的基态使用优选出的cc-pV6Z基组、对SiH的基态使用优选出的aug-cc-pV5Z基组进行几何构型与谐振频率的计算并进行单点能扫描, 且将扫描结果拟合成了解析的Murrell-Sorbie函数. 与实验结果及其他理论计算结果的比较表明, 本文关于SiH自由基光谱常数（D_e,R_e, ω_e, B_e, α_e和ω_eχ_e）的计算结果达到了很高的精度. 采用多体项展式理论导出了SiH₂（C_2v, X¹A₁）自由基的解析势能函数, 其等值势能图准确再现了它的离解能和平衡结构特征. 同时还给出了SiH₂（C_2v, X¹A₁）自由基对称伸缩振动等值势能图中存在的两个对称鞍点, 对应于SiH+H→SiH₂反应, 势垒高度为0.5084 eV. 关键词： 2')" href="#">SiH₂ Murrell-Sorbie函数 多体项展式理论 解析势能函数     

Eu$lt;sup$gt;2+$lt;/sup$gt;的掺杂浓度对BaAl$lt;sub$gt;2$lt;/sub$gt;Si$lt;sub$gt;2$lt;/sub$gt;O$lt;sub$gt;8$lt;/sub$gt;：Eu$lt;sup$gt;2+$lt;/sup$gt;荧光粉发光特性的影响

采用化学共沉淀法一次煅烧工艺合成了BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉.用X射线衍射仪和荧光分光光度计等对BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉的相结构、发光性能进行了测试.结果表明：化学共沉淀法一次煅烧工艺合成的BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉为单相;其激发光谱分布在240—410 nm的波长范围,峰值位于320 nm处,可以被InGaN管芯产生的350—410 nm辐射有效激发;在365 nm近紫外光的激发下,测得其发射光谱是位于465 nm附近的宽带峰.BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉的发光强度随Eu²⁺浓度的增大逐渐加强,当Eu²⁺掺杂的摩尔分数为3.5%时,发光强度达到最大值,而后随掺杂浓度的增加而减小,发生浓度猝灭;根据Dexter能量共振理论,该浓度猝灭是由于Eu²⁺的离子间交换相互作用引起的. 关键词： 2Si₂O₈：Eu²⁺')" href="#">BaAl₂Si₂O₈：Eu²⁺ 发光特性 蓝色荧光粉 化学共沉淀法     

钙钛矿型锰氧化物(La$lt;sub$gt;0.8$lt;/sub$gt;Eu$lt;sub$gt;0.2$lt;/sub$gt;)$lt;sub$gt;4/3$lt;/sub$gt;Sr$lt;sub$gt;5/3$lt;/sub$gt;Mn$lt;sub$gt;2$lt;/sub$gt;O$lt;sub$gt;7$lt;/sub$gt;的磁性和电性研究

采用传统固相反应法制备钙钛矿型锰氧化物 (La_0.8Eu_0.2)_4/3Sr_5/3Mn₂O₇多晶样品, X-射线衍射分析表明, 样品(La_0.8Eu_0.2)_4/3Sr_5/3Mn₂O₇结构呈现良好的单相. 通过磁化强度随温度的变化曲线(M-T)、不同温度下磁化强度随磁场的变化曲线(M-H)和电子自旋共振谱发现: 在300 K以下, 随着温度的降低, 样品先后经历了二维短程铁磁有序转变 (T_C^2D ≈ 282 K)、三维长程铁磁有序转变(T_C^3D ≈ 259 K)、奈尔转变(T_N ≈ 208K)和电荷有序转变(T_CO ≈ 35 K); 样品 (La_0.8Eu_0.2)_4/3Sr_5/3Mn₂O₇在T_N以下, 主要处于反铁磁态; 在T_C^3D达到370 K时, 样品处于铁磁-顺磁共存态, 在370 K以上时样品进入顺磁态. 此外, 分析电阻率随温度的变化曲线(ρ-T)得到: 样品在金属-绝缘转变温度(T_P ≈ 80 K)附近出现最大磁电阻值, 其位置远离T_C^3D, 表现出非本征磁电阻现象, 其磁电阻值约为61%. 在T_CO以下, 电阻率出现明显增长, 这是由于温度下降使原本在高温部分巡游的e_g电子开始自发局域化增强所致. 通过对 (La_0.8Eu_0.2)_4/3Sr_5/3Mn₂O₇的ρ-T 曲线拟合, 发现样品在高温部分的导电方式基本遵循小极化子的导电方式. 关键词： 磁性 电性 金属-绝缘转变温度 电子自旋共振     

Ce$lt;sup$gt;3+$lt;/sup$gt;在LiBaBO$lt;sub$gt;3$lt;/sub$gt;中的发光特性及晶体学格位

采用固相法制备了LiBaBO₃：Ce³⁺发光材料.测得LiBaBO₃：Ce³⁺材料的发射光谱为一不对称的单峰宽谱,主峰位于440 nm;监测440 nm发射峰,可得其激发光谱为一主峰位于370 nm的宽谱.利用van Uitert公式计算了Ce³⁺取代LiBaBO₃中Ba²⁺时所占晶体学格位,得出438 nm发射带归属于九配位的Ce³⁺发射,而469 nm发射带起源于八配位的Ce³⁺发射.研究了Ce³⁺浓度对LiBaBO₃：Ce³⁺材料发光强度的影响,结果显示,随Ce³⁺浓度的增大,发光强度呈现先增大后减小的趋势,Ce³⁺浓度为3mol%时强度最大,造成其浓度猝灭的原因为电偶极-偶极相互作用.引入Li⁺,Na⁺或K⁺可增强LiBaBO₃：Ce³⁺材料的发射强度.利用InGaN管芯（370 nm）激发LiBaBO₃：Ce³⁺材料,获得了很好的蓝白光发射,色坐标为（x=0.291,y=0.297）. 关键词： 白光发光二极管 3：Ce³⁺')" href="#">LiBaBO₃：Ce³⁺ 晶体学格位 发光特性     

Nd3+掺杂的氧化镧钇透明激光陶瓷的光谱性能研究

采用传统无压烧结工艺制备了Nd³⁺掺杂的Y_2-2xLa_2xO₃(x=0.08)透明陶瓷并对其光谱性能进行了研究. 结果表明：Nd³⁺:Y_1.84La_0.16O₃透明陶瓷在780—850 nm的波长范围内有较宽的吸收带. 当Nd³⁺掺杂量为1.5at%时，在820 nm和激光二极管抽运的808 nm处的吸收截面分别为σ_abs(820 nm)=1.81×10^-20 cm²，σ_abs(808 nm)=1.54×10^-20 cm². 最强的发射峰位于1078 nm处，并具有荧光寿命长、发射带宽宽、量子效率高等特点. 加入La₂O₃后，基质的光谱品质参数X_Nd由1.6减小到0.46，因此和⁴F_3/2—⁴I_11/2跃迁相对应的荧光分支比β_J,11/2增大为56.82%. Nd³⁺:Y_1.84La_0.16O₃透明陶瓷的这些性质有利于高效率的激光输出和超短锁模激光脉冲的实现. 关键词： 氧化镧钇透明陶瓷 光谱性能 3+')" href="#">Nd³⁺     

Sr2+掺杂荧光粉Ca2Nb2O7：Eu3+的发光特性

采用高温固相法制备出Ca_1.97-xSr_xNb₂O₇：3%Eu³⁺（x=0.10,0.50,1.0,1.5,1.97）红色荧光粉,研究了Ca_1.97-xSr_xNb₂O₇：3%Eu³⁺的发光特性及Sr²⁺的浓度对该荧光粉发光性质的影响。随着Sr²⁺浓度的改变,Ca_2-xSr_xNb₂O₇：Eu³⁺的XRD呈现不同的相。Ca_1.97Nb₂O₇：3%Eu³⁺（x=0）的激发光谱中,302 nm附近的强宽带来自于O^2-→Eu³⁺电荷转移跃迁,272 nm附近的肩峰来自于NbO^7-₆基团的电荷转移跃迁,350~600 nm范围内的锐锋属于Eu³⁺的特征4f-4f组内跃迁。在398 nm激发下,发射光谱的最强峰位于616 nm,属于Eu³⁺的⁵D₀→⁷F₂电偶极跃迁,发射出强烈的红光。当Ca²⁺逐渐被Sr²⁺取代时,Ca_2-xSr_xNb₂O₇：Eu³⁺的各激发峰的强度先提高后降低,且O^2-→Eu³⁺电荷转移跃迁发生明显红移。少量Sr²⁺的掺杂可以有效提高Ca_2-xSr_xNb₂O₇：Eu³⁺ 的红光发射强度,当x=0.01时该荧光粉的红光发射达到最强,可以被紫外LED芯片激发。     

Effects of (LiCe) co-substitution on the structural and electrical properties of CaBi2Nb2O9 ceramics

The piezoelectric, dielectric, and ferroelectric properties of the (LiCe) co-substituted calcium bismuth niobate (CaBi₂Nb₂O₉, CBNO) are investigated. The piezoelectric properties of CBNO ceramics are significantly enhanced and the dielectric loss tanδ decreased. This makes poling using (LiCe) co-substitution easier. The ceramics (where □ represents A-site Ca²⁺ vacancies, possess a pure layered structure phase and no other phases can be found. The Ca_0.88(LiCe)_0.04□_0.04Bi₂Nb₂O₉ ceramics possess optimal piezoelectric properties, with piezoelectric coefficient (d₃₃) and Curie temperature (T_C) found to be 13.3 pC/N and 960 ℃, respectively. The dielectric and piezoelectric properties of the (LiCe) co-substituted CBNO ceramics exhibit very stable temperature behaviours. This demonstrates that the CBNO ceramics are a promising candidate for ultrahigh temperature applications.     

Electrical properties of neodymium doped CaBi4Ti4O15 ceramics

Neodymium doped bismuth layer structure ferroelectrics (BLSFs) ceramics CaBi_4−xNd_xTi₄O₁₅ (x=0, 0.25, 0.50, 0.75) were prepared by solid-state reaction method. X-ray diffraction pattern showed that single phase was formed when x=0-0.75. The refined lattice parameters showed that a (b) axes decrease at x=0.25 and increase with more Nd³⁺ dopant. The effects of Nd³⁺ doping on the dielectric and ferroelectric properties of CaBi₄Ti₄O₁₅ ceramics are studied. Nd³⁺ dopant decreased the Curie temperature linearly, and the dielectric loss, tan δ, as well. The remnant polarization of Nd³⁺ doped CaBi₄Ti₄O₁₅ ceramics was increased by 80% at x=0.25, while more Nd³⁺ dopant decreased the remnant polarization. CaBi_3.75Nd_0.25Ti₄O₁₅ ceramics had the largest piezoelectric constant d₃₃. The structure and properties of CaBi_4−xNd_xTi₄O₁₅ ceramics showed that Nd³⁺ may occupy different crystal locations when Nd³⁺ content x is less than 0.25 and more than 0.50.     

Electron spin resonance of localized copper states in Sr1?xAxCuO2 ceramics (A = Li+, K+, La3+; x ≤ 0.15)

The orthorhombic modification of SrCuO₂ ceramics and its derivatives Sr_1−x A _x CuO₂ (A = Li⁺, K⁺, La³⁺) were studied using the ESR and x-ray diffraction methods. Orthorhombic and axial-symmetry paramagnetic centers caused by oxygen defects in samples were detected. From comparing the ESR and x-ray phase data, it follows that the oxygen distribution in ceramics is inhomogeneous. __________ Translated from Fizika Tverdogo Tela, Vol. 47, No. 8, 2005, pp. 1482–1485. Original Russian Text Copyright ? 2005 by Ivanova, Jacyna-Onyszkiewicz, Augustyniak-Yablokova, Yablokov, Shustov.     

Templated Grain Growth of Textured Piezoelectric Ceramics

Crystallographic texturing of polycrystalline ferroelectric ceramics offers a means of achieving significant enhancements in the piezoelectric response. Templated grain growth (TGG) enables the fabrication of textured ceramics with single crystal-like properties, as well as single crystals. In TGG, nucleation and growth of the desired crystal on aligned single crystal template particles results in an increased fraction of oriented material with heating. To facilitate alignment during forming, template particles must be anisometric in shape. To serve as the preferred sites for epitaxy and subsequent oriented growth of the matrix, the template particles need to be single crystal and chemically stable up to the growth temperature. Besides templating the growth process, the template particles may also serve as seed sites for phase formation of a reactive matrix. This process, referred to as Reactive TGG (RTGG), has been used to obtain highly oriented Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃, Sr_0.53Ba_0.47Nb₂O₆, and (Na_1/2Bi_1/2)TiO₃-BaTiO₃. Highly oriented Bi₄Ti₃O₁₂, Sr₂Nb₂O₇, CaBi₄Ti₄O₁₅, Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃, Sr_0.53Ba_0.47Nb₂O₆ and (Na_1/2Bi_1/2)TiO₃-BaTiO₃ ceramics have been produced by TGG. The resulting ceramics show texture levels up to 90%, and significant enhancements in the piezoelectric properties relative to randomly oriented ceramics with comparable densities. For example, piezoelectric coefficients of textured piezoelectrics are from 2 to 3 times higher than polycrystalline ceramics and as high as 90% of the single crystal values. In textured PMN-PT, a low field (< 5 kV/cm) piezoelectric coefficient (d ₃₃) of ～1600 pC/N was obtained with > 0.3% strain (at 50 kV/cm). The high field dielectric and electromechanical properties of textured perovskites are more hysteretic than those of single crystals, probably as a result of clamping by the residual template particles, residual random grains, the presence of non-ferroelectric second phases, and a wide orientation distribution. Lateral clamping of one grain by another may also be an important factor in fiber-textured samples. Means to further improve the quality of texture and thus properties of textured piezoelectric ceramics by TGG are presented.     

Phase transformation behavior and dielectric characteristics of BaTi1−x(Al1/2Nb1/2)xO3 (0.01≤x≤0.40) ceramics

Microstructure, phase transformation behavior and dielectric properties of BaTi_1−x(Al_1/2Nb_1/2)_xO₃ (0.01≤x≤0.40) ceramics were investigated. A high level of (Al_1/2Nb_1/2)⁴⁺ substitution for Ti⁴⁺ ions was not conducive to the stability of the perovskite structure and resulted in the formation of BaAl₂O₄. As x was increased, lattice constants and unit cell volume decreased, reached a minimum at x=0.10 and then increased. The BaTi_1−x(Al_1/2Nb_1/2)_xO₃ ceramics at room temperature experienced a transformation from ferroelectric to paraelectric phase with increasing (Al_1/2Nb_1/2)⁴⁺ concentration. Meanwhile, permittivity of the BaTi_1−x(Al_1/2Nb_1/2)_xO₃ ceramics was markedly reduced, while Q value was slightly increased. Frequency dispersion of dielectric peak was obviously increased as x was increased from 0.01 to 0.10. It is of great interest that a dielectric abnormity represented by a broad dielectric peak at 200-400 K was observed for the composition with x=0.40.     

Dielectric and piezoelectric properties of barium-modified Aurivillius-type Na0.5Bi4.5Ti4O15

In this study, monophasic Ba_x(Na_0.5Bi_0.5)_1−xBi₄Ti₄O₁₅ (x=0.03, 0.06, 0.09 and 0.12) ceramics fabricated from the powders synthesized via the solid-state reaction route exhibited relaxor behavior. X-ray diffraction analysis revealed that the barium-modified Na_0.5Bi_4.5Ti₄O₁₅ ceramics have a pure four-layer Aurivillius phase structure. Dielectric properties and phase transitions were studied and are explained in terms of lattice response of these ceramics. A shift in ferroelectric–paraelectric phase transition (T_c) to lower temperatures and a corresponding increase in permittivity peak with increasing concentration of Ba²⁺ are also observed. The decrease of orthorhombicity in the lattice structure by the larger Ba²⁺ ion incorporation, indicating an approach of a and b parameters, results in lower Curie temperature. The piezoelectric activity of Na_0.5Bi_4.5Ti₄O₁₅ (NBT) ceramics was significantly improved by the modification of barium. The Curie temperature T_c and piezoelectric coefficient d₃₃ for the composition with x=0.12 were found to be 635 °C and 21 pC/N, respectively. The relationship of polarization with lattice response is discussed.     

Co2+-Ti4+和Cu2+-Nb5+离子取代BaFe12O19单晶体中Fe3+离子的研究

本文对用Co²⁺-Ti⁴⁺和Cu²⁺-Nb⁵⁺离子取代BaFe₁₂O₁₉单晶体中Fe³⁺离子进行了研究,以Bi₂O₃作为助熔剂生长出了BaFe_12-2xCo_x²⁺Ti_x⁴⁺O₁₉(x=0;0.04;0.09;0.13;0.27和0.68)以及BaFe_12-x[Nb_1/3⁵⁺Cu_2/3²⁺]_xO₁₉(x=0;0.28;0.44和0.60)这两系列的单晶体,测定了100—300K温度范围内样品的磁化强度σ与单轴各向异性常数K₁,我们发现,对Co²⁺-Ti⁴⁺取代的样品,当x≤0.09时,其σ与K₁随x的增加而缓慢增加;当x>0.09时,其σ与K₁随x的增加而迅速降低,至x=1.1时,K₁变为零,对Nb⁵⁺-Cu²⁺取代的样品,其σ值在整个成份范围内基本保持不变,且有缓慢增加趋势;而K₁值则随x增加而单调下降,提出了取代离子在M型六角铁氧体中可能的分布模型来解释我们的结果。 关键词：     

Dy含量对红色长余辉发光材料Sr3Al2Ｏ6:Eu2＋,Dy3＋性能的影响

采用溶胶凝胶法制备了Sr₃Al₂Ｏ₆:Eu^2＋,Dy^3＋红色长余辉发光材料,利用X射线衍射仪对材料的物相进行了分析,结果表明,1200℃下制备的样品的物相为Sr₃Al₂Ｏ₆,少量的Eu和Dy掺杂没有影响样品的相组成.采用荧光分光光度计、照度计测定了样品的发光特性.结果表明Sr₃Al₂Ｏ关键词： 红色长余辉 3Al₂Ｏ₆')" href="#">Sr₃Al₂Ｏ₆ 溶胶凝胶法     

Piezoelectric properties of PbHfO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary ceramics

(1 – x)Pb(Hf_1–yTi_y)O₃–x Pb(Mg_1/3Nb_2/3)O₃ (x = 0.1 ～ 0.25, y = 0.555) ternary piezoelectric ceramics were prepared using the two‐step precursor method. Morphotropic phase boundary (MPB) compositions, located at x = 0.18 ～ 0.22, were confirmed using X‐ray diffraction and by their dielectric, piezoelectric and ferroelectric properties. The optimum dielectric and piezoelectric properties were achieved for the MPB composition 0.8Pb(Hf_0.445Ti_0.555)O₃–0.2Pb(Mg_1/3Nb_2/3)O₃, with dielectric permittivity ε_r, piezoelectric coefficient d₃₃, planar electromechanical coupling k_p and Curie temperature T_C being on the order of 2800, 680 pC/N, 70% and 276 °C, respectively. Of particular significance is that the new ternary ceramics exhibit comparable piezoelectric and electromechanical properties to commercial PZT5H ceramics, but with much improved T_C, showing a potential for applications at elevated temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

非化学计量和掺杂对(Na1/2Bi1/2)0.92Ba0.08TiO3陶瓷电性能的影响

研究了非化学计量和掺杂对无铅压电陶瓷(Na_1/2Bi_1/2)_0.92Ba_0.08TiO₃的压电性能及去极化温度的影响.研究发现A位非化学计量可以提高陶瓷的压电性能;B位掺杂对材料电学性能的影响规律类似于Pb(Ti,Zr)O₃系压电陶瓷的相关规律;由于非化学计量和掺杂会影响到A位离子对B位离子与氧离子形成的BO₆八面体的耦合作用,影响到畴的稳定性,从而影响 关键词： 无铅压电陶瓷 非化学计量 掺杂 电性能