溶胶-凝胶K_(0.5)Bi_(0.5)TiO_3陶瓷的高温XRD研究

采用溶胶-凝胶法成功制备出K0.5Bi0.5TiO3(KBT)纳米微粉,并利用此微粉烧结出成瓷良好的KBT陶瓷。用XRD法测定了KBT陶瓷粉末室温和高温(600°C)时的点阵常数,确定KBT的高温相为立方结构(点群为m3m)并指标化其衍射线,给出了KBT陶瓷粉末的多晶XRD数据。     

钛酸铋钾陶瓷的sol-gel法制备及性能表征

以硝酸钾,五水硝酸铋,钛酸四丁酯为原料,采用sol-gel法制备了K0.5Bi0.5TiO3(KBT)压电陶瓷,分别用DSC-TGA、XRD和FT-IR分析了凝胶的热演化、晶化与相变过程,研究了KBT陶瓷的介电性能。结果表明:600℃烧结即可合成纯钙钛矿相KBT粉体;sol-gel法比传统固相反应法的烧结温度降低约200℃,且能有效控制晶粒长大,抑制杂相生成。所制KBT陶瓷的介电温谱的分析结果显示KBT为典型的弛豫型铁电体。     

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.     

Ba6-3xEu8+2xTi18O54介电陶瓷XRD及XPS研究

采用溶胶-凝胶(Sol-Gel)法成功制备出Ba6-3xEu8 2xTi18O54(BET,x=2/3)微粉,并利用此微粉烧结出成相良好的BET微波介电陶瓷。用X-射线衍射(XRD)法测定了BET粉末室温点阵常数,确定BET室温相为正交结构(空间群为Pbam)并指标化其衍射线,给出了BET粉末的多晶XRD数据。用X-射线光电子能谱(XPS)法测定了BET中Eu离子4d电子的结合能为135 eV,确定Eu离子为 3价、样品为充分氧化的BET陶瓷。     

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．     

机械力化学法制备Pb(Sc0.5Ta0.5)O3弛豫铁电陶瓷微粉

用机械力化学法合成了单相Pb(Sc0.5Ta0.5)O3（R）弛豫铁电陶瓷微粉，并对球磨5h得到的陶瓷粉体和未经球磨的原料进行了热处理研究，实验结果表明，单相Pb(Sc0.5Ta0.5)O3可在球磨7h得到，TEM图像显示，晶粒尺寸为30－40mm，与根据Scheerer公式计算的结果吻合，5h粉体的热处理结果显示，焦绿矿相并未因球磨过程而在煅烧中不出现，原 粉体的热处理结果也显示出焦绿矿在1350℃温度下煅烧4h，仍有少量存在，比较实验的结果表明，在制备Pb(Sc0.5Ta0.5)O3的过程中，初始原料必须经过充分球磨才可实现单相目标产物的合成。     

In_2O_3掺杂Bi_(0.5)(Na_(0.82)K_(0.18))_(0.5)TiO_3无铅压电陶瓷的研究

以准同型相界组成Bi0.5(Na0.82K0.18)0.5TiO3(BNT)为基础配方,In2O3为改性剂,研究了In2O3掺杂量对Bi0.5(Na0.82K0.18)0.5TiO3无铅陶瓷晶体结构和电性能的影响。XRD分析表明,所有样品的相结构均为纯钙钛矿固溶体。陶瓷的晶粒尺寸随掺杂量的增加而增加。介电常数-温度曲线显示陶瓷具有两个介电反常峰tf和tm,在tm的介电常数εm随掺杂量的增加而下降,tf和tm都随掺杂量的增加向高温移动。当In2O3摩尔分数为0.1%时,压电性能达最大值:d33=141pC/N,kp=0.32。     

退火处理对0.5PZN-0.5PZT陶瓷弛豫性的影响

采用常规陶瓷工艺制备了Pb(Zn_(1/3)Nb_(2/3))_(0.5)(Zr_(0.5)Ti_(0.5))_(0.5)O_3 (0.5PZN-0.5PZT)铁电陶瓷,并在氧气氛下进行退火.运用XRD、直流电导率和介电温度谱测试氧气氛退火前后陶瓷相结构与电性能的变化,并对弛豫性与微结构的关系进行探讨.结果表明,氧气氛退火可有效补偿体系中的氧空位,降低四方相含量,材料的弛豫性显著增强.     

K0.5Na0.5NbO3掺杂对BaTiO3陶瓷介电性能的影响

采用固相反应法制备了(K0.5Na0.5)NbO3(KNN)-BaTiO3陶瓷.借助XRD、SEM和阻抗分析仪研究了KNN掺杂对BaTiO3陶瓷微观结构及介电性能的影响.结果表明:掺杂KNN的BaTiO3陶瓷均呈现出单一钙钛矿结构.KNN掺杂能够促进BaTiO3陶瓷的烧结并提高其致密度.随KNN掺杂量(摩尔分数)的增加...     

凝胶自燃烧法合成Bi_(0.5)Na_(0.5)TiO_3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。     

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.     

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.     

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.     

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。     

(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.     

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.