Calculation shown that the refraction index of Ge_0.6Si_0.4/Sistrained-layer superlattice n≈3.64, when L_w=9 nm and L_b=24 nm. Analgorithm of numerical iteration for effective refraction index isemployed to obtain di...Calculation shown that the refraction index of Ge_0.6Si_0.4/Sistrained-layer superlattice n≈3.64, when L_w=9 nm and L_b=24 nm. Analgorithm of numerical iteration for effective refraction index isemployed to obtain different effective refraction indexes atdifferent thickness (L). As a result, the thickness ofGe_0.6Si_0.4/Si strained-layer superlattice optical waveguide, L≤363nm, can be determined, which is very important for designingwaveguide devices. An optical waveguide can be made into a nanometerdevice by using Ge_0.6 Si_0.4/Si strained-layer superlattice.展开更多
采用高温固相法合成Ca取代Sr3Al0.6Si0.4O4.4F0.6∶Ce3+中Sr的Sr3-x Ca x Al0.6Si0.4O4.4F0.6∶Ce3+荧光粉。由于Sr3Al0.6Si0.4O4.4F0.6∶Ce3+中Sr具有十配位Sr(1)和八配位Sr(2),所以激活剂离子Ce3+也具有两个不同的占位。结合Ce3+的光...采用高温固相法合成Ca取代Sr3Al0.6Si0.4O4.4F0.6∶Ce3+中Sr的Sr3-x Ca x Al0.6Si0.4O4.4F0.6∶Ce3+荧光粉。由于Sr3Al0.6Si0.4O4.4F0.6∶Ce3+中Sr具有十配位Sr(1)和八配位Sr(2),所以激活剂离子Ce3+也具有两个不同的占位。结合Ce3+的光谱结果和Van Uitert经验公式,分别研究了十配位Ce(1)3+和八配位Ce(2)3+的猝灭浓度和荧光寿命,指出是由于Ca的掺入减小了Ce(1)3+发光中心,增加了Ce(2)3+发光中心,从而出现随着Ca/Sr比增加,样品在400 nm激发下发光强度减小,而在460 nm激发下发光强度增大的现象。同时,Ca的掺入增强了粉体发光的热稳定性。调节Ca含量可以使粉体实现从绿黄色到黄色的发光,表明Sr3-x Ca x Al0.6Si0.4-O4.4F0.6∶Ce3+荧光粉是一款潜在的适合近紫外和蓝光激发的白光LED用荧光粉。展开更多
A series of CeMn2（Si1-xGex）2（x = 0.2, 0.4, 0.6, 0.8） compounds are prepared by the arc-melting method. All the samples primarily crystallize in the Th Cr2Si2-type structure. The temperature dependences of zero-fie...A series of CeMn2（Si1-xGex）2（x = 0.2, 0.4, 0.6, 0.8） compounds are prepared by the arc-melting method. All the samples primarily crystallize in the Th Cr2Si2-type structure. The temperature dependences of zero-field-cooled（ZFC） and FC magnetization measurements show a transition from antiferromagnetic（AFM） state to ferromagnetic（FM） state at room temperature with the increase of the Ge concentration. For x = 0.4, the sample exhibits two kinds of phase transitions with increasing temperature： from AFM to FM and from FM to paramagnetic（PM） at around TN-197 K and T C-300 K,respectively. The corresponding Arrott curves indicate that the AFM–FM transition is of first-order character and the FM–PM transition is of second-order character. Meanwhile, the coexistence of positive and negative magnetic entropy changes can be observed, which are corresponding to the AFM–FM and FM–PM transitions, respectively.展开更多
The Li 4.4Al 0.4Si 0.6O 4-xLi 3BO 3 (x=0 to 0.5) ion conductors were prepared by the sol-gel method. The powder and sintered samples were characterized by DTA-TG, XRD, SEM and ac impedance techniqu...The Li 4.4Al 0.4Si 0.6O 4-xLi 3BO 3 (x=0 to 0.5) ion conductors were prepared by the sol-gel method. The powder and sintered samples were characterized by DTA-TG, XRD, SEM and ac impedance techniques. The temperature of the preparation of powder patterns decreased by this method as compared to that of the preparation in solid state reaction. The conductivity and sinterability increased with Li 3BO 3 increasing from x=0 to 0.2 in the Li 4.4Al 0.4Si 0.6O 4-xLi 3BO 3 solid electrolytes. The particle size of the sintered pellets is about 0.12 μm. The maximum conductivity at 20 ℃ is 3.165×10 -5 S·cm -1 for Li 4.4Al 0.4Si 0.6O 4-0.2Li 3BO 3.展开更多
The present work is devoted to investigating the microstructure,magnetism and magnetocaloric effects of Si- and Mn-rich FeMn(P,Si) alloys.The Mn-substituted alloys with Fe_(2-x)Mn_xP_(0.4)Si_(0.6)(x=1.25,1.30,1.35,1.4...The present work is devoted to investigating the microstructure,magnetism and magnetocaloric effects of Si- and Mn-rich FeMn(P,Si) alloys.The Mn-substituted alloys with Fe_(2-x)Mn_xP_(0.4)Si_(0.6)(x=1.25,1.30,1.35,1.40,1.45 and 1.50) were prepared by high-energy ball milling and solid-state reaction.Experimental results show that the alloys crystallized into a majority Fe_2P-type hexagonal structure,coexisting with minor amounts of(Mn,Fe)_3Si and(Mn,Fe)_5Si_3 phases.The Curie temperature decreased linearly from 321 to 266 K with increasing Mn content from 1.25 to 1.50 in Fe_(2-x)Mn_xP_(0.4)Si_(0.6) alloys.The first-order magnetic phase transition became weakened and the second-order magnetic phase transition became dominated with increasing Mn content.Fe_(0.75)Mn_(1.25)P_(0.4)Si_(0.6) alloy presents a maximum isothermal magnetic-entropy changes of 7.2 J(kg K)^(-1) in a magnetic field change of 0-1.5 T.The direct measurement shows that Fe_(0.7)Mn_(1.3)P_(0.4)Si_(0.6) and Fe_(0.65)Mn_(1.35)P_(0.4)Si_(0.6) alloys exhibit a maximum adiabatic temperature change of 1.8 K in a magnetic field change of 0-1.48 T.The thermal hysteresis for all alloys is less than 4 K.These experimental results reveal that Fe_(2-x)Mn_xP_(0.4)Si_(0.6) alloys could be a candidate material for magnetic refrigeration.展开更多
文摘Calculation shown that the refraction index of Ge_0.6Si_0.4/Sistrained-layer superlattice n≈3.64, when L_w=9 nm and L_b=24 nm. Analgorithm of numerical iteration for effective refraction index isemployed to obtain different effective refraction indexes atdifferent thickness (L). As a result, the thickness ofGe_0.6Si_0.4/Si strained-layer superlattice optical waveguide, L≤363nm, can be determined, which is very important for designingwaveguide devices. An optical waveguide can be made into a nanometerdevice by using Ge_0.6 Si_0.4/Si strained-layer superlattice.
文摘采用高温固相法合成Ca取代Sr3Al0.6Si0.4O4.4F0.6∶Ce3+中Sr的Sr3-x Ca x Al0.6Si0.4O4.4F0.6∶Ce3+荧光粉。由于Sr3Al0.6Si0.4O4.4F0.6∶Ce3+中Sr具有十配位Sr(1)和八配位Sr(2),所以激活剂离子Ce3+也具有两个不同的占位。结合Ce3+的光谱结果和Van Uitert经验公式,分别研究了十配位Ce(1)3+和八配位Ce(2)3+的猝灭浓度和荧光寿命,指出是由于Ca的掺入减小了Ce(1)3+发光中心,增加了Ce(2)3+发光中心,从而出现随着Ca/Sr比增加,样品在400 nm激发下发光强度减小,而在460 nm激发下发光强度增大的现象。同时,Ca的掺入增强了粉体发光的热稳定性。调节Ca含量可以使粉体实现从绿黄色到黄色的发光,表明Sr3-x Ca x Al0.6Si0.4-O4.4F0.6∶Ce3+荧光粉是一款潜在的适合近紫外和蓝光激发的白光LED用荧光粉。
基金Project supported by the Beijing Natural Science Foundation,China(Grant No.2152034)the National Natural Science Foundation of China(Grant Nos.11274357 and 51271196)
文摘A series of CeMn2（Si1-xGex）2（x = 0.2, 0.4, 0.6, 0.8） compounds are prepared by the arc-melting method. All the samples primarily crystallize in the Th Cr2Si2-type structure. The temperature dependences of zero-field-cooled（ZFC） and FC magnetization measurements show a transition from antiferromagnetic（AFM） state to ferromagnetic（FM） state at room temperature with the increase of the Ge concentration. For x = 0.4, the sample exhibits two kinds of phase transitions with increasing temperature： from AFM to FM and from FM to paramagnetic（PM） at around TN-197 K and T C-300 K,respectively. The corresponding Arrott curves indicate that the AFM–FM transition is of first-order character and the FM–PM transition is of second-order character. Meanwhile, the coexistence of positive and negative magnetic entropy changes can be observed, which are corresponding to the AFM–FM and FM–PM transitions, respectively.
文摘The Li 4.4Al 0.4Si 0.6O 4-xLi 3BO 3 (x=0 to 0.5) ion conductors were prepared by the sol-gel method. The powder and sintered samples were characterized by DTA-TG, XRD, SEM and ac impedance techniques. The temperature of the preparation of powder patterns decreased by this method as compared to that of the preparation in solid state reaction. The conductivity and sinterability increased with Li 3BO 3 increasing from x=0 to 0.2 in the Li 4.4Al 0.4Si 0.6O 4-xLi 3BO 3 solid electrolytes. The particle size of the sintered pellets is about 0.12 μm. The maximum conductivity at 20 ℃ is 3.165×10 -5 S·cm -1 for Li 4.4Al 0.4Si 0.6O 4-0.2Li 3BO 3.
基金supported by the National Natural Science Foundation of China(51671045 and 51601073)the Fundamental Research Funds for the Central Universities(DUT16ZD209)+1 种基金the National Magnetic Confinement Fusion Science Program(2013GB107003 and 2015GB105003)the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University(SKLSP201607)
文摘The present work is devoted to investigating the microstructure,magnetism and magnetocaloric effects of Si- and Mn-rich FeMn(P,Si) alloys.The Mn-substituted alloys with Fe_(2-x)Mn_xP_(0.4)Si_(0.6)(x=1.25,1.30,1.35,1.40,1.45 and 1.50) were prepared by high-energy ball milling and solid-state reaction.Experimental results show that the alloys crystallized into a majority Fe_2P-type hexagonal structure,coexisting with minor amounts of(Mn,Fe)_3Si and(Mn,Fe)_5Si_3 phases.The Curie temperature decreased linearly from 321 to 266 K with increasing Mn content from 1.25 to 1.50 in Fe_(2-x)Mn_xP_(0.4)Si_(0.6) alloys.The first-order magnetic phase transition became weakened and the second-order magnetic phase transition became dominated with increasing Mn content.Fe_(0.75)Mn_(1.25)P_(0.4)Si_(0.6) alloy presents a maximum isothermal magnetic-entropy changes of 7.2 J(kg K)^(-1) in a magnetic field change of 0-1.5 T.The direct measurement shows that Fe_(0.7)Mn_(1.3)P_(0.4)Si_(0.6) and Fe_(0.65)Mn_(1.35)P_(0.4)Si_(0.6) alloys exhibit a maximum adiabatic temperature change of 1.8 K in a magnetic field change of 0-1.48 T.The thermal hysteresis for all alloys is less than 4 K.These experimental results reveal that Fe_(2-x)Mn_xP_(0.4)Si_(0.6) alloys could be a candidate material for magnetic refrigeration.
