高频热等离子体制备Mn掺杂的棒状纳米氧化锌

以锌粉和MnCl2为反应物,在高频感应热等离子体中制备了Mn掺杂的ZnO纳米棒. 通过XRD, FESEM, TEM和HRTEM对产物的结构、形貌进行了分析. 随着Mn掺杂量的增加,ZnO的衍射峰向小角方向移动,证实掺杂的Mn原子进入了ZnO晶体的晶格,ZnO纳米棒的长径比逐渐减小,未掺杂的ZnO纳米棒直径约为30 nm,长度约为2 mm,当掺杂的Mn/Zn摩尔比为4%时,掺杂后的ZnO纳米棒直径约为100 nm,长度约为200 nm. Mn掺杂的ZnO纳米棒显示出了室温铁磁性特征,且随Mn掺杂含量提高而增强,当Mn掺杂量由0.25%增加到4%时,ZnO纳米棒的矫顽力从78 Oe上升到149 Oe.     

掺杂的Ni-Zn铁氧体磁性材料的制备与性能

以分析纯Fe2O3,NiO,ZnO,Al2O3,Pr6O11和WO3为原料,以Ni0.5Zn0.5MxFe2–xO4(M=Al,Pr,W;x=0～0.04)为基本配方,采用一步合成法制备了Ni–Zn铁氧体陶瓷,研究了掺杂对Ni–Zn铁氧体相组成、显微形貌和电磁性能的影响。结果表明:掺杂Al3+,Pr3+和W6+的Ni–Zn铁氧体均能形成结晶完好的尖晶石相结构。材料致密,无晶粒异常长大。适当的金属阳离子替代可有效降低材料的磁损耗和介电损耗,提高截止频率,同时使铁氧体保持较高初始磁导率,高饱和磁化强度,高Curie温度等优良性能,从而制得高性能大功率高频Ni–Zn系铁氧体磁芯。     

Al掺杂量对ZnO多晶性能影响的研究

采用固相反应法制备了六方纤锌矿结构Zn1-xAlxO(0≤x≤0.005)系列多晶,探究了Al掺杂对ZnO多晶的微观形貌和热电输运性质的影响.Al掺杂促使ZnO晶粒长大联结,晶界减少,x=0.005时出现在晶界分布的ZnAl2O4尖晶石相.各组分样品经二次烧结后,电阻率均比对应组分的一次烧结样品增大1~2个数量级.掺杂后样品由ZnO的半导体行为转变为电阻率显著下降的金属行为,一次烧结样品在x=0.004有最小的室温电阻率~10 mΩ·cm,主要由于掺杂使样品载流子浓度和迁移率显著提高;300~950 K下掺杂样品热电势的绝对值和功率因子均随温度升高而增大,x=0.004时有最大的室温功率因子~0.11 mW/m·K2.综合得到ZnO中Al掺杂的饱和固溶度在0.004~0.005之间.     

不同稀土Nd3+掺杂含量对锰锌铁氧体吸波性能的影响

采用水热合成法制备出锰锌稀土复合铁氧体Mn0.4Zn0.6NdxFe2-xO4(x=0,0.03,0.06,0.09),以X射线衍射仪(XRD),矢量网络分析仪(VNA)和透射电子显微镜(TEM)为表征手段,研究不同稀土Nd3+掺杂含量对锰锌铁氧体微观结构及吸波性能的影响.实验表明:当掺杂量x=0.03时,制备的样品纯相单一,具有类球形结构,反射损耗值最低为-8.36 dB.随着Nd3+含量的不断增加,晶格常数减小,反射损耗值逐渐增大,样品的吸波性能不佳,说明掺杂适量的Nd3+能够提高材料的吸波性能.     

Ce掺杂ZnO的晶体结构、发光和光催化性能的不同机理

采用溶胶凝胶法合成了一系列Ce掺杂ZnO粉晶。采用XRD, UV-VIS, FT-IR, PL技术及以亚甲基蓝溶液脱色反应为模型,研究了Ce掺杂ZnO晶体结构、光学带隙、成键、光致发光及光催化性能产生的不同机理。结果表明:低含量Ce掺杂和高含量Ce掺杂对ZnO结构和性能产生的机理存在差异。低含量Ce掺杂时,ZnO晶格参数及Zn-O键长因原子半径大的Ce~(3+)替代原子半径小的Zn~(2+)而增加,光学带隙因Burstein-Moss效应而宽化,结晶性能因ZnO成核空间增加而提高,青蓝色发光峰因结晶性能提高而减弱。高含量Ce掺杂时,ZnO晶格参数及Zn-O键长因Ce~(3+)Ce~(4+)转化而减小,光学带隙因Ce~(3+)占据Zn~(2+)格位而减小,结晶性能因氧化铈包覆作用并降低结晶速率而提高,青蓝色发光峰随缺陷增加而增强。Ce掺杂ZnO光催化能力随光学带隙减小而提高。光催化性能最优Ce掺杂量为2%。FT-IR表明系列Ce掺杂ZnO均含有Zn-O和Ce-O-Zn等成键。     

Y~(3+)掺杂对Mn-Zn铁氧体结构和性能的影响及正己烷磁流体的制备

用改进的化学共沉淀法首次合成了稀土钇离子掺杂的Mn0.8Zn0.2YxFe2-xO4(其中x=0、0.02、0.04、0.06、0.08、0.1)铁氧体纳米颗粒,利用X射线粉末衍射(XRD)和振动样品磁强计(VSM)研究了温度和Y3+掺杂量对磁性纳米颗粒结构和磁性能的影响。通过加入十二烷基硫酸钠(SDS)控制纳米颗粒的大小,并用油酸作为表面改性剂,制备了稳定的Mn0.8Zn0.2Y0.02Fe1.98O4正己烷磁流体,使用红外光谱(FTIR)、热重(TGA)和透射电镜(TEM)研究了p H值对油酸包裹的影响。研究发现:通过对化学共沉淀法进行改进,在沸腾的情况下制备出了目前饱和磁化强度最高的Mn0.8Zn0.2Fe2O4纳米磁性颗粒(Ms=63.8 A?m2?kg?1),适当掺杂Y3+不会破坏铁氧体的尖晶石结构并且随着掺杂量的增加,饱和磁化强度Ms先增加后减小,当x=0.02时Ms最大;在p H=5的乙醇-水体系中进行改性,油酸的包裹量最大,制备出的Mn0.8Zn0.2Y0.02Fe1.98O4正己烷磁流体长期放置不会分层。     

溶胶-凝胶法制备Co掺杂ZnO薄膜及其室温铁磁性(英文)

以聚乙烯醇为溶剂,用溶胶-凝胶法在石英玻璃基底表面制备了Zn1-xCoxO(x=0.08,0.10,0.12)稀磁半导体薄膜。研究表明:Zn1-xCoxO薄膜均为纤锌矿结构,没有出现与Co相关的杂质相,Co2+取代Zn2+位置进入ZnO的晶格,样品的光学带隙随Co含量的增加而减小。Zn1-xCoxO稀磁半导体薄膜具有室温铁磁性,其饱和磁化强度(Ms)和矫顽力(Hc)均随Co2+含量(x=0.08,0.10,0.12)的增加而逐渐增大,Ms分别为1.12×104,1.45×104A/m和1.66×104A/m,Hc分别约为2.31×105,3.30×105A/m和4.26×105A/m,并讨论了其铁磁性的来源。     

厚度对溶胶-凝胶法制备锂掺杂ZnO薄膜性能的影响

采用溶胶-凝胶旋涂法在玻璃衬底上制备了不同厚度的ZnO:Li半导体薄膜.采用X射线衍射仪和扫描电子显微镜分析了薄膜的物相结构和形貌,用Hall效应测量仪常温下测量薄膜的电学性能.结果表明:该薄膜具有高度的c轴择优取向性,所有薄膜只有1个(002)衍射峰,并且衍射强度随着膜厚增加而加强.ZnO:Li薄膜晶粒呈柱状,晶粒直径不随膜厚改变,约为40 um.ZnO:Li薄膜为P型导电,薄膜越厚,其电学性能与晶体结晶越好,(002)方向择优取向生长越明显.电阻率随着膜厚增加而减小,最小的电阻率为1.32×102(Ω·cm).载流子-空穴浓度为3.546×1016/cm3,迁移率为1.34cm2/(V·s).ZnO:Li薄膜在可见光范围内的透过率达到90%,薄膜对紫外光的吸收与厚度有关.     

N-Mn-TiO2/AC粒子电极的制备及其降解性能研究

以传统活性炭(AC)粒子电极为载体，采用溶胶-凝胶法制备TiO₂/AC粒子电极以及掺N、掺Mn、N-Mn共掺杂改性的TiO₂/AC粒子电极，并将几种粒子电极应用于三维光电系统，考察其对实际印染废水的处理性能。XRD表征结果表明，TiO₂成功负载于AC表面且以锐钛矿晶型为主，N元素并未取代晶格氧，而是进入TiO₂晶格间隙，加快了电荷转移，Mn元素则以间隙掺杂形式进入TiO₂晶格，加快了光生空穴(h+)的转移；SEM、EDS和FT-IR结果显示，相比TiO₂/AC粒子电极，N-Mn-TiO₂/AC粒子电极比表面积显著增大，含氧官能团明显增加；印染废水降解实验结果表明，当实际印染废水中COD、NH₄⁺-N、TN分别为1 600～1 800、25～40、40～60 mg/L时，N-Mn-TiO₂/AC三维光电体系对COD、NH₄⁺-N...     

Er^(3+)掺杂对立方焦绿石陶瓷结构与介电性能的影响EI北大核心CSCD

采用固相反应法制备(Bi1.5–x Erx Zn0.5)(Zn0.5Nb1.5)O7(BEZN,x=0、0.05、0.10、0.15、0.20、0.25、0.30)陶瓷,研究了Er3+替代Bi3+对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7(BZN)陶瓷结构与介电性能的影响。结果表明:当Er3+掺杂量x<0.15 mol时,样品为单一α-BZN相;当x≥0.15 mol时,出现第二相。用分子动力学计算Er3+分别进入A、B位的溶解能结果可知,此时Er3+可能已进入B位。随Er3+掺杂量增加,Er3+进入晶格,BEZN陶瓷密度从6.999 g/cm3减小到6.680 g/cm3,有明显细化晶粒作用。一定频率(1 MHz)条件下,峰值介电常数随Er3+掺杂量增加而减小,弛豫峰温度范围介电常数变化量Δε逐渐减小,即弛豫峰逐渐宽化和平坦。     

铜（Ⅱ）掺杂Li3V2（PO4）3/C的结构与性能

用一步碳热还原法制备了Li3V2-xCux(PO4)3/C(x=0.00、0.02、0.05、0.08、0.10、0.15)复合正极材料,并研究了掺杂对材料结构、微观形貌、充放电性能的影响。结果表明掺杂少量铜(Ⅱ)不会影响材料Li3V2(PO4)3的基本结构,但会在Li3V2(PO4)3中形成电子缺陷,提高晶体内部原子的无序化程度,降低极化和电荷转移电阻。从而改善材料的电化学性能。Li3V1.98Cu0.02(PO4)3/C的10 C放电容量比Li3V2(PO4)3/C提高了20 mA.h/g,具有较好的倍率性能。     

锂离子电池Li2Fe1-xVxSiO4/C复合正极材料的合成、结构形貌和电化学性能

采用液相预处理和固相反应相结合的方法合成了聚阴离子型锂离子电池Li2Fe1-xVxSiO4/C（x=0,0.1,0.3,0.5）复合正极材料,采用XRD、SEM、EDX和电化学测试对材料进行了表征,研究了钒掺杂对材料结构、形貌和电化学性能的影响。结果表明所有样品均为正交晶系,属P21mn空间群,钒掺杂量x=0.1时样品晶格常数发生明显变化,晶胞呈c轴方向拉长的立方体,导致了材料的比容量和循环性能下降;所有样品均为纳米至亚微米尺寸颗粒,且随钒掺杂量的增加而增大,但x=0.5时样品的电化学性能最优。在常温和0.2C倍率下初始放电容量为124.3mAh/g,循环10次后容量无衰减,可逆放电容量仍高达126.2mAh/g,显示了良好的循环性能和应用前景。     

电池正极材料Li3V2-2x/3Mnx（PO4）3/C的制备及性能研究

以V2O5、NH4H2PO4、Li2CO3、(CH3COO)2Mn.4H2O原料,以葡萄糖和抗坏血酸为复合还原剂及碳源,通过常温还原-低温烧结法制备锂离子电池正极材料Li3V(2-2x/3)Mnx(PO4)3/C(x=0,0.03,0.06,0.09,0.12)。通过X射线衍射(XRD),扫描电镜(SEM),恒电流充放电测试对该正极材料的物相、结构、微观形貌以及电化学性能进行了表征。结果表明,Mn2+的掺杂对磷酸钒锂电化学性能的发挥影响很大,其中当锰掺杂量x=0.09时材料表现出最佳的电化学性能,0.2 C倍率条件下首次放电比容量131 mAh/g,循环50次后容量衰减仅为4.02%。     

Effects of Li doping and point defect on the magnetism of ZnO

The magnetism sources and magnetic mechanism of Li doping and point defect, which coexist in the presence of hexagonal wurtzite ZnO, are controversial. To solve these problems, the effects of Li doping and point defect on the magnetism of ZnO were studied using geometry optimization and energy calculation based on the first-principle generalized gradient approximation + U (GGA + U) method of density functional theory. Results showed that the coexistence of Li doping and Zn vacancy can achieve ferromagnetic long-range order, and the Curie temperature of the doping system can achieve room temperature. In addition, results showed that magnetic moments are significantly different when the structures of the systems are also different with the same doping amount and doping method, which are advantageous for the enhancement of the magnetic properties of dilute magnetic semiconductors. The magnetism source of Zn₁₄LiO₁₆ is the hybrid coupling electron exchange effect between O-2p and Zn-3d orbits. With the coexistence of Li replacing Zn and Zn vacancy, the closest relative distance between doping and vacancy leads to the lowest formation energy and highest stability. In the condition of the highest stability of the ground state, all the doping systems of Li replacing Zn and O vacancy, doping system of interstitial Li and Zn vacancy, and doping system with the coexistence of Li replacing Zn, interstitial Li, and Zn vacancy are non-magnetic, which are considered worthless in the design and preparation of diluted magnetic semiconductors (DMSs).     

铈掺杂镍锌铁氧体的制备与性能研究

用高分子凝胶法制备了稀土元素铈掺杂的镍锌铁氧体粉Ni0.5Zn0.5CexFe2-xO4,并对产物结构和电磁性能进行了表征。结果表明,当Ce3+的掺杂摩尔数x为0.1时,800℃煅烧后会形成立方晶系尖晶石结构的镍锌铁氧体晶相。与Ni0.5Zn0.5Fe2O4铁氧体相比,在8.2~12.4 GHz频率范围内掺杂铈元素的Ni0.5Zn0.5Ce0.1Fe1.9O4铁氧体的tanδm值降低,而其tanδe值升高,平均值可达0.527。     

Concentration threshold effect on properties of zinc‐doped lithium niobate crystals

Results of LiNbO₃:Zn researches often diverge because sharp changes in physicochemical characteristics of the system melt‐crystal that occur at doping are usually not taken into consideration. When a series of doped crystals is grown Zn is usually added to the melt with step 1.5‐2 mol%. This obstructs detection of exact threshold concentration. We have grown LiNbO₃:Zn crystals doped by 4.0÷9.0 mol% ZnO with step ~1 mol%. Around the dopant, threshold concentration step was narrowed to ~0.1 mol%. We have researched physicochemical properties of the system melt‐crystal and structure evolution by Raman spectroscopy and full‐profile analysis of XRD. We have detected exact threshold concentration for LiNbO₃:Zn and concluded that crystals doped by prethreshold concentrations of ZnO are the best for most applications because of the higher optical homogeneity.     

Investigations on ferromagnetism of Li and Mn codoped LiZnN by first-principles calculations

Electronic structures and magnetic properties of Li and Mn codoped LiZnN systems were investigated by using the first-principles calculations. Mn-doped LiZnN systems preferred the antiferromagnetic states, while Mn/Li codoped LiZnN systems were ferromagnetic and more stable than the Mn-doped LiZnN systems. The magnetic moments mostly arose from Mn-3d states, which hybridized with N-2p and Li-2s states near the Fermi level. The ferromagnetic coupling was suggested to be attributed to the p-d hybridization by the Mn–N–Mn chain. The results indicated that nonstoichiometry of Li was very essential for the ferromagnetism of Li(Zn,Mn)N system.     

Sb掺杂对(K0.49Na0.51)0.94Li0.06(Nb0.94Ta0.06)O3无铅压电陶瓷结构与性能的影响

采用固相反应法制备(K0.49Na0.51)0.94Li0.06Nb0.94SbxTa0.06-xO3(KNNLSxT0.06-x,x=0.00～0.06)无铅压电陶瓷,研究了Sb的掺杂量对陶瓷晶体结构与压电性能的影响。X射线衍射结果表明:随着Sb掺杂量x的增加,陶瓷的晶体结构由正交相向四方相转变,并在x=0.04～0.05时出现正交相逐渐转变为四方相的多型相转变(PPT),在x=0.04时具有较佳的性能:压电常数d33=258 pC/N,平面机电耦合系数kp=54%,机械品质因素Qm=61以及较高的居里温度Tc=405℃。     

Lithium aluminum-layered double hydroxide chlorides (LDH): Formation enthalpies and energetics for lithium ion capture

Layered aluminum double hydroxide chloride sorbents, LiCl∙Al₂(OH)₆.nH₂O, Li-LDH, have shown promising application in selective Li extraction from geothermal brines. Maintaining LiCl uptake capacity and retaining a long cycle life are critical to widespread application of sorbent materials. To elucidate the energetics of Li capture, enthalpies of LDH with different Li content have been measured by acid solution calorimetry. The formation enthalpies generally become less exothermic as the Li content increases, which indicates that Li intercalation destabilizes the structure, and the enthalpies seem to approach a limit after the Li content x = 2Li/Al exceeds 1. To improve stability, metal doping of the aluminum LDH structure with iron was performed. Introduction of a metal with greater electron density but a similar ionic radius was postulated to improve the stability of the LDH crystal structure. The calorimetric results from Fe-doped LDH samples corroborate this as they are more exothermic than LDH-lacking Fe. This suggests that Fe doping is an effective way to stabilize the LDH phase.