凝胶自燃烧法合成Bi0.5Na0.5TiO3纳米粉体

以Bi(NO3)3·5H2O、NaNO3和Ti(OC4H9)4为原料,采用凝胶自燃烧法合成了Bi0.5Na0.5TiO3纳米粉体,研究了粉体的晶相结构。结果表明:所合成的粉体粒子大小均匀,晶相单一,不需高温处理便能直接形成钙钛矿结构超细粉末。粉末经压片,1125℃烧结2h即可获得致密的烧结体,其d为98.1%。用SEM观察,烧结样品的平均粒径为2μm。     

水热法制备K0.5Bi0.5TiO3陶瓷粉体及其介电性能研究

采用水热法合成了K0.5Bi0.5TiO3(KBT)无铅压电陶瓷粉体.运用X线衍射(XRD)分析了KOH浓度及反应时间对产物物相的影响;利用扫描电镜(SEM)和透射电镜(TEM)观察研究了粉体的形貌.结果表明,增大碱浓度(4～12 mol/L)和延长反应时间都有利于KBT纳米粉体的合成.在220℃,KOH的起始浓度12 mol/L水热合成48 h的纯KBT相呈立方形结构,晶型规整,晶粒尺寸约为100nm.由水热法制备的粉体在1060℃烧结,获得介电损耗为0.05的致密压电陶瓷材料.     

共沉淀法制备Y2O2SO4:Eu3+荧光粉及其光致发光研究

采用商业Y(NO3)3·6H2O、Eu(NO3)3·6H2O、(NH4)2SO4和NaOH为实验原料,通过共沉淀法制备了Y2O2SO4:Eu3+荧光粉。利用热分析(DTA-TG-DTG)、傅里叶变换红外(FT-IR)光谱、X射线衍射(XRD)、扫描电子显微镜(SEM)和光致发光(PL)光谱等手段对合成的粉体进行了表征。结果表明,当(NH4)2SO4引入到反应体系中时,前驱体具有非晶态结构,且在空气气氛中800℃煅烧2h能转化为单相的Y2O2SO4粉体,该Y2O2SO4粉体呈准球形,粒径范围分布在0.5~1.0μm之间,团聚较严重。PL光谱分析表明,在270nm紫外光激发下,Y2O2SO4:Eu3+荧光粉呈红光发射,主发射峰位于620nm,归属于Eu3+的5D0→7F2跃迁。Eu3+的猝灭浓度是5 mol%,其对应的荧光寿命为1.22 ms。另外,当(NH4)2SO4未引入到反应体系中时,采用类似的方法合成了Y2O3:Eu3+荧光粉,并对Y2O2SO4:Eu3+和Y2O3:Eu3+荧光粉的PL性能进行了比较。     

熔盐法合成钛酸铋钾陶瓷粉体

以K2CO3,Bi2O3和TiO2为反应物,KCl为熔盐,通过熔盐法在600℃成功合成纯钙钛矿结构K0.5Bi0.5TiO3(KBT)无铅陶瓷粉体。探寻了制备过程中影响粉体颗粒大小和形貌的工艺参数,并对影响机理进行了探讨。结果表明,与传统固相法相比,熔盐法合成温度显著降低且颗粒平均粒径明显减小。固相法合成的粉体平均粒径为115nm,KCl含量5%和20%的熔盐法合成粉体平均粒径为78nm和67nm。此外,实验发现随着熔盐量的增加,易合成各向异性的棒状粉体。     

溶胶凝胶自蔓延燃烧法制备NiZnCoCu铁氧体粉体

以金属硝酸盐和柠檬酸等为原料,利用溶胶凝胶自蔓延燃烧法制备了Ni0.5–xZn0.5Co0.1CuxFe1.9O4(x=0,0.10,0.15,0.20)粉体,将粉体在800℃下热处理2 h,通过FT-IR、XRD、SEM和VSM对粉体的物相结构和磁性能进行分析。结果表明,自蔓延燃烧粉体以Ni Zn Co铁氧体为主晶相,其中含有Fe2O3杂相,煅烧后杂相消失。煅烧有效推动了晶界移动,实现晶粒的长大。煅烧前后两类粉体的饱和磁化强度都随着Cu的含量增加而逐渐减小,同时矫顽力也都先减小后增加,其中煅烧粉体的磁性能较自蔓延粉体均得到提升。     

Pb(Ti_0.48)Zr_(0.52))O_3微晶的水热合成工艺研究

以TiO2粉体、Pb(NO3)2和ZrOCl2.8H2O为原材料,KOH为矿化剂,水热合成了Pb(Ti0郾48Zr0郾52)O3微晶。研究了KOH浓度、反应时间、反应温度、Pb/Z(r+Ti)、原料浓度以及矿化剂种类等因素对水热合成Pb(Ti0郾48Zr0郾52)O3微晶的影响,确定了水热合成Pb(Ti0郾48Zr0郾52)O3微晶的最佳工艺参数。对水热合成的Pb(Ti0郾48Zr0郾52)O3粉体用XRD和SEM进行表征,得到了颗粒均匀、团聚少、粒径0郾5～1郾0μm的Pb(Ti0郾48Zr0郾52)O3粉体颗粒。     

Bi2O3过量对熔盐法制备Bi4Ti3O12粉体的影响

以NaCl-KCl熔盐法制备了各向异性的Bi4Ti3O12粉体,研究了w(Bi2O3过量)对粉体的影响,优化了制备Bi4Ti3O12粉体的工艺参数。结果表明:w(Bi2O3过量)为7.5%,1100℃烧结2h所得到的Bi4Ti3O12粉体微观形貌最佳,并探讨了Bi4Ti3O12粉体在熔盐中的生长机理。     

锆钛酸铅纳米陶瓷粉体的低温水热合成

使用TiO2粉体、ZrOCl2.8H2O、Pb(NO3)2为原料,KOH为矿化剂,Pb/(Zr Ti)=1.0,在160℃下反应3 h,获取了分散性较好的锆钛酸铅纳米粉体。用X-射线衍射仪、扫描电子显微镜等测试手段分析了实验结果,结果表明,所得锆钛酸铅纳米粉体颗粒为四方晶相钙钛矿结构,呈立方体状,粒子粒径为0.5~2.0μm,同时分析了在本实验条件下锆钛酸铅纳米粉体可能的合成机理。     

前驱体溶液pH值对柠檬酸盐法合成Na_(0.5)Bi_(0.5)TiO_3微粉的影响

采用柠檬酸盐法合成了钙钛矿相的Na0.5Bi0.5TiO3粉体,利用TG-DTA、XRD、SEM及激光粒度仪对Na0.5Bi0.5TiO3粉体进行了分析表征,讨论了前驱体溶液pH值对合成粉体的影响。结果表明,当前驱体溶液pH=8.5,柠檬酸与金属离子摩尔比r(C/Mn+)=1.25,水浴温度为80℃,煅烧温度为600℃时,所制备出的Na0.5Bi0.5TiO3晶体呈球形,其颗粒细小,粒径为100~200 nm。相同条件下,当pH=2.5时产物主要是富含Na、Ti、O的棒状物质。pH=6.5时所得粉体主要是Na0.5Bi0.5TiO3相,粉体颗粒呈球状,粒径为500~600 nm,其中存在少量的块状颗粒,粒径分布不均匀。pH=10.5时产物中含有较多Bi3Ti4O12杂相,粒径较大。     

两步法快速退火对PSTT5铁电薄膜性能的影响

采用射频磁控溅射法在LSCO/Pt/Ti/SiO2/Si(100)衬底上制备了 0.95Pb(Sc0.5Ta0.5)O3-0.05PbTiO3(PSTT5)铁电薄膜.研究了不同的快速退火(RTA)工艺对PSTT5薄膜的结晶性能和铁电性能的影响.实验结果表明,经两步法快速退火,PSTT5薄膜具有完全钙钛矿结构且呈(220)取向.PSTT5薄膜的铁电性能测试结果也表明,采用两步法RTA处理的PSTT5薄膜具有更好的铁电性能,其剩余极化强度(2Pr)可达25.4 μC/cm2.     

In0.5Ga0.5As/In0.5Al0.5As应变耦合量子点的形貌和光学性质

提出了利用分子束外延方法生长In0.5Ga0.5As/In0.5Al0.5As应变耦合量子点,并分析量子点的形貌和光学性质随GaAs隔离层厚度变化的特点.实验结果表明,随着耦合量子点中的GaAs隔离层厚度从2 nm增加到10 nm,In0.5Ga0.5As量子点的密度增大、均匀性提高,Al原子扩散和浸润层对量子点PL谱的影响被消除,而且InAlAs材料的宽禁带特征使其成为InGaAs量子点红外探测器中的暗电流阻挡层.由此可见,选择合适的GaAs隔离层厚度形成InGaAs/InAlAs应变耦合量子点将有益于InGaAs量子点红外探测器的研究.     

Donor-acceptor interactions in Al0.5In0.5P

Dopant interactions are considered between Mg-acceptor atoms and various donor species, including the deep donor; oxygen; and the shallow donors, Te, S, and Si, in Al_0.5In_0.5P. While each of these donor species is shown to suppress Mg diffusion and enhance Mg incorporation in Al_0.5In_0.5P, careful analysis of the concentration profiles for these various donor species reveals subtle differences in the shape of the donor and acceptor dopant profiles, suggesting subtle differences in both the type of donor-acceptor interactions involved and in the effectiveness of the various donor species at suppressing Mg diffusion. Oxygen, in particular, is shown to have a profound effect on Mg diffusion in Al_0.5In_0.5P uniform-composition layers, while other donor species are less effective at suppressing Mg diffusion. Such differences suggest that a chemical bonding effect or complex formation may be more dominant between Mg and oxygen, while electrical compensation likely plays a larger relative role between Mg and the shallow-donor species.     

Ohmic contacts ton-type In0.5Ga0.5P

The contact properties of alloyed Ni/Au-Ge/Mo/Au metallization to npoststagger+In_0.5Ga_0.5P epilayers grown by gas-source molecular beam epitaxy on GaAs substrates are reported. A minimum specific contact resistance of 10⁻⁵ Ωcm² was obtained forn = 2 × 10¹⁹ cm⁻³ material after alloying at 360° C for 20 sec. Above this temperature outdiffusion of lattice elements and reactions of the metallization with the In_0.5Ga_0.5P lead to severe morphological changes and degraded contact properties. From the temperature dependence of the contact resistance, thermionic emission was identified as the predominant current transport mechanism in these contacts.     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的介电压电性能

研究了(Na1-xKx)0.5Bi0.5TiO3体系无铅压电陶瓷的介电、压电性能，通过XRD分析，发现随着x的增加，陶瓷的晶体结构由三方相逐渐转变为四方相，x=0．16～0．20范围内具有三方和四方共存相结构，为该体系的准同型相界(MPB)，材料在MPB附近具有最佳的压电性能．测试了陶瓷的介电温谱，表明该体系陶瓷为弛豫型铁电体，电滞回线表明陶瓷在升温过程中发生铁电-反铁电-顺电相变．     

(1-3x)NBT-2xKBT-xBT系无铅压电陶瓷性能研究R&D

通过XRD分析,发现该体系陶瓷都能形成单一的钙钛矿型固溶体,并在0.025≤x≤0.035范围内具有三方和四方共存结构,为该体系的准同型相界。当x=0.035时,陶瓷的压电常数d33达到150 pC/N,平面机电耦合系数kp达到0.297 7,均高于相应两元体系的压电性能。测定了该体系陶瓷材料的介电常数–温度曲线和电滞回线,发现该体系陶瓷的介电温谱都存在两个介电反常峰,分别对应于陶瓷材料的铁电–反铁电和反铁电–顺电相变。同时,该体系陶瓷具有弛豫铁电体性质。     

Ordering and disordering of doped Ga0.5In0.5P

The band gap of Ga_0.5In_0.5P is reported as a function of doping level and growth rate. The lowest band gaps are obtained for hole concentrations of about 2 × 10¹⁷ cm⁻³. For samples doped p-type above 1 × 10¹⁸ cm⁻³, the band gap increases dramatically, regardless of growth rate. This effect is shown to be the result of disordering during growth rather than a change in the equilibrium surface structure with doping. The doping level dependence of the band gap of Ga_0.5In_0.5P samples grown at higher and lower growth rates differs for selenium and zinc doping even though the effects of high doping are the same for both dopants.     

水热法制备纳米Na0.5Bi0.5TiO3粉体

采用Bi(NO3)3?5H2O、Ti(OC4H9)4为原料,在水热条件下研究了影响Na0.5Bi0.5TiO3(BNT)晶体生长和形成的各个影响因素,诸如:水热反应的温度、时间,NaOH浓度以及原料的种类等。实验结果表明,反应温度在160~180℃,保温时间在4~24 h,NaOH浓度为4~12 mol/L时,能制备出纯净的、立方形的纳米Na0.5Bi0.5TiO3晶体,其颗粒线度尺寸为15~55 nm。若温度低于160℃,Na0.5Bi0.5TiO3结晶程度低;若高于180℃,易形成Bi4Ti3O12。当NaOH浓度低于4 mol/L时,Na0.5Bi0.5TiO3晶相少,主要呈Bi4Ti3O12;当其高于12 mol/L时,产物主要是非晶态物质。     

High‐Performance Near‐IR Photodetector Using Low‐Bandgap MA0.5FA0.5Pb0.5Sn0.5I3 Perovskite

Photodetectors with ultrafast response are explored using inorganic/organic hybrid perovskites. High responsivity and fast optoelectronic response are achieved due to the exceptional semiconducting properties of perovskite materials. However, most of the perovskite‐based photodetectors exploited to date are centered on Pb‐based perovskites, which only afford spectral response across the visible spectrum. This study demonstrates a high‐performance near‐IR (NIR) photodetector using a stable low‐bandgap Sn‐containing perovskite, (CH₃NH₃)_0.5(NH₂CHNH₂)_0.5Pb_0.5Sn_0.5I₃ (MA_0.5FA_0.5Pb_0.5Sn_0.5I₃), which is processed with an antioxidant additive, ascorbic acid (AA). The addition of AA effectively strengthens the stability of Sn‐containing perovskite against oxygen, thereby significantly inhibiting the leakage current. Consequently, the derived photodetector shows high responsivity with a detectivity of over 10¹² Jones ranging from 800 to 970 nm. Such low‐cost, solution processable NIR photodetectors with high performance show promising potential for future optoelectronic applications.     

Effects of trimethylindium on the purity of In0.5Al0.5P and In0.5Al0.5as epilayers grown by metalorganic chemical vapor deposition

In_0.5Al_0.5P lattice-matched to GaAs and In_0.5A1_0.5As lattice-matched to InP epilayers were grown by atmospheric pressure metalorganic chemical vapor deposition (AP-MOCVD). The effect of trimethylindium on the purity of the as-grown layers was systematically studied using secondary ion mass spectroscopy (SIMS), deep level transient spectroscopy (DLTS), and capacitance-voltage (C-V) measurements. The SIMS results showed that oxygen is the main impurity in all layers and the oxygen concentration in InAlP was approximately one to four orders of magnitude higher than the oxygen concentration found in InALAs when the same indium source was used, indicating that more oxygen was introduced by the phosphine source than by the arsine source. Two electron traps in the InAlP epilayers and four electron traps in the InALAs epilayers were observed in this study. When a high-purity indium source was used, the best InAlP epilayer showed only one deep electron trap at 0.50 eV while the best InALAs epilayer showed no deep levels measured by DLTS. In addition, we also found that a high concentration of oxygen is related to the high resistivity in both material systems; this suggests that semi-insulating (SI) materials can be achieved by oxygen doping and high quality conducting materials can only be obtained through the reduction of oxygen. The oxygen concentration measured by SIMS in the best InALAs epilayer was as low as 3 × 10¹⁷ cm⁻³.