Double hysteresis loops and enhanced mechanical quality factor of Mn-doped 0.75PMN-0.25PT ceramics

Relaxor ferroelectric 0.75 Pb(Mg_1/3Nb_2/3)O₃-0.25PbTiO₃ (0.75PMN-0.25PT) ceramics with Mn-doping concentration of 0%, 1%, 2% and 3 mol% were prepared by two-step sintering. The phase composition, microstructure, dielectric property, ferroelectric property, piezoelectric property and electromechanical property were investigated. Results indicate that all ceramics exhibit pure perovskite phases and high density. Mn-doping induces some decrease in dielectric constant ε_r, dielectric loss tanδ, remnant polarization P_r, piezoelectric coefficient d₃₃, and electromechanical coupling coefficient k_p, while significant increase in mechanical quality factor Q_m and the figure of merit (FOM) of 0.75PMN-0.25PT ceramics. For 3 mol% Mn-doped 0.75PMN-0.25PT ceramics, Q_m enhances by 1449%, FOM increases by 923%, and tanδ decreases by 67%, which makes it more suitable for high power applications. Interestingly, double P-E loops are observed in 3 mol% Mn-doped 0.75PMN-0.25PT ceramics. The phenomenon was investigated by the symmetry-conforming principle of point defects and the internal bias field.     

Synthesis and properties of manganese-doped barium titanate

An oxalate route for the production of BaTiO₃ has been modified to incorporate Mn (upto 2%) as a dopant and the reaction sequence has been studied. The resulting Mn-doped BaTiO₃ exhibits a dielectric constant with an increasing insensitivity to temperature and applied a.c. field as the Mn content is increased. These samples possess a high electrical resistivity even after treatment in hydrogen at 1100°C and are therefore suitable as dielectric for multilayer capacitors with base metal electrodes.     

高补偿硅的光敏感特性

对电阻率为5 ·cm的p型单晶硅,在高温条件下采用扩散金属锰的方法,得到高补偿硅。并在室温(25℃)和液氮温度(196℃)下,测试了这种高补偿硅材料对光强的敏感性。测试结果表明:这种材料是一种光敏感材料,其敏感性受外加的电压、样品的温度及补偿后样品的电阻率影响。     

掺锰对不同导电类型硅材料热敏特性的影响

采用电阻率为5 ·cm的p型单晶硅和n型单晶硅,通过高温扩散金属锰的方法,可得到两种类型的热敏材料。测试发现,选择适当的扩散温度和时间,这两种类型的热敏材料一致性都较好。对n型硅掺锰,得到的是小正温度系数热敏材料,其B值在620 K左右;对p型硅掺锰,得到的是负温度系数热敏材料,其B值在4 200 ~4300 K之间。     

Self-template synthesis of lychee like Mn-doped Co2P yolk-shell spheres for enhanced hydrogen evolution reaction activity

Designing an electrocatalyst for hydrogen production from water splitting that is highly efficient, stable, and free of noble metals is necessary but challenging. The phosphorus compound is considered a viable candidate for producing hydrogen from water split, but its electrocatalytic performance needs further improvement. Herein, we present an easy and straightforward method for constructing Mn-doped Co₂P yolk-shell lychee spheres. The Co nano prisms are used as a self-sacrificing template to conduct an ion exchange reaction with manganese ions, constructing Co oxide yolk-shell spheres with Mn–Co hydroxide nano-blocks. After in-suit phosphating at low temperature, Mn-doped Co₂P with yolk-shell structure and lychee morphology is formed. The Mn-doped Co₂P with an optimized Mn and Co molar ratio (0.125) exhibits excellent hydrogen evolution performance in alkaline and acidic electrolyte. The overpotentials can reach 10 mA cm^?2 at 98 mV and 72 mV, respectively, and the Mn–Co₂P-0.125 catalyst has faster electron transfer efficiency and larger electrochemically active surface area. The experimental results ascertain that doping an appropriate amount of Mn significantly changes the morphology and structure, thereby affecting the exposure of active sites, and modulating the electronic structure around Co₂P. Under the dual regulation of morphology and electronic structure, the electrocatalytic process is accelerated, enhancing its catalytic activity.     

Mn掺杂对尖晶石型NiFe1.97Pd0.03O4-δ催化剂脱硝性能的影响

采用生物模板法,通过掺杂Mn对尖晶石型NiFe_1.97Pd_0.03O_4-δ催化剂中的Fe离子进行取代,制备一系列不同Mn掺杂量的NiFe_1.97-xMn_xPd_0.03O_4-δ催化剂（x=0、0.01、0.02、0.05、0.10）,并在单管固定床反应器中进行H₂-SCR脱硝性能评价。运用X射线衍射仪（XRD）、场发射扫描电子显微镜（FE-SEM）、程序升温-脱附（NH₃-TPD）和程序升温还原（H₂-TPR）以及傅里叶红外光谱仪（FTIR）等手段对催化剂进行表征、分析。结果表明：适量Mn的掺杂不仅可以提高活性物种Pd在催化剂上的分散度,还显著提高了其催化剂表面的总酸量及其氧化还原能力,从而提高了NiFe_1.97Pd_0.03O_4-δ催化剂在低温下的H₂-SCR脱硝活性,并拓宽了其催化活性温度窗口。在实验范围内,NiFe_1.92Mn_0.05Pd_0.03O_4-δ催化剂在150℃下的NO转化率高达95%,且在150~200℃温度区间内,NO转化率均在90%以上。     

Dielectric and energy storage properties of Mn-doped Ba0.3Sr0.475 La0.12Ce0.03TiO3 dielectric ceramics

Microstructure, temperature and frequency dependent dielectric and energy storage properties of Ba_0.3Sr_0.475La_0.12Ce_0.03Ti_1−xMn_xO₃(x = 0 − 0.005) have been investigated with X-ray diffractometer, and scanning electron microscope, broad band dielectric spectrometer and ferroelectric analyzer. The doping of Mn substantially decreased the dielectric loss, but made some of Ce³⁺ be oxidized to Ce⁴⁺ entering into B-site, which resulted in the formation secondary phases. For the Mn-doped composition, extremely low dielectric loss (10⁻⁵ order of magnitude at 10 kHz) could be obtained at room temperature. The relaxation mechanism at low temperature is of the dipole type for the undoped composition and that at high temperature (>500 K) is governed by the trap controlled ac conduction, respectively. The energy storage properties were improved by the doping with Mn due to the increase of insulation. Maximum energy density of 0.953 J/cm³ could be obtained for x = 0.003 composition with the BDS of 247 kV/cm and efficiency of 93%.     

锰掺杂对PMN-PZT陶瓷介电性能的影响

研究了锰掺杂对富锆PMN-PZT（铌镁酸铅一锆钛酸铅）陶瓷材料的相组成、微观结构、介电性能等方面的影响，并对实验结果作出物理机理的解释。实验结果表明：适量的锰掺杂有助于陶瓷晶粒的生长，并能有效地降低PMN-PZT陶瓷材料的介电常数和介电损耗，在锰掺杂量为3．0％（原子分数）时，εr：197、tanδ=0．15％，作为用于红外热释电探测器的陶瓷材料具有良好的介电性能。     

纯无机体系合成高度稳定和分散的纳米银胶

采用固相反应+放电等离子体两步法成功地制备了TiFeSb及Mn掺杂的(Ti0.75Mn0.25)FeSb两种P型Half-Heusler 热电材料,并对这两种新型热电材料体系的X射线衍射谱进行了计算模拟和试验研究,同时对其组织结构和热电性能进行了表征.试验结果表明,合成材料的X射线衍射试验谱可以与模拟计算谱很好的吻合;50℃时,TiFeSb的ZT值为0.011,而(Ti0.75Mn0.25)FeSb体系因Mn掺杂后电阻率大幅度下降,Seebeck系数变化不大,热导率下降了1.2 W·m-1.K-1,使得最终的功率因子较TiFeSb体系提高了3.5倍,ZT值提高了4.3倍.     

Complex permittivity and relaxation processes in CaCu3Ti(4−x)MnxO12

The effects of Mn-doping on CaCu₃Ti₄O₁₂ (CCTO), i.e. the electrical properties of CaCu₃Ti_(4−x)Mn_xO₁₂ were studied in order to get a deep insight into the origin of the colossal dielectric constant of CCTO. It was found that 1 mol% substitution of Mn for Ti decreases the dielectric constant largely to a factor of 1/100, supporting the point of view that the native defects are responsible for the dielectric response of CCTO.