For the first time detailed measurements of the DOS （density of states） for Ti3AIC2 and Ti3SiC2 are presented at temperatures between T = 10 and 100 K. For Ti3AIC2 a DFT （density functional theory） simulation of l...For the first time detailed measurements of the DOS （density of states） for Ti3AIC2 and Ti3SiC2 are presented at temperatures between T = 10 and 100 K. For Ti3AIC2 a DFT （density functional theory） simulation of lattice dynamics is compared to experimental data demonstrating a noticeable difference between the spectra especially below 40 meV. In the case of Ti3SiC2 the DFT model is augmented with MD （molecular dynamics） simulations resulting in the measured and simulated spectra resembling one another more closely but still having significant differences below 40 meV. Within the experimental spectra, there are features up to and including 20 meV which are unaccounted for by the simulation. Tracing individual atoms generated by the computer models suggests anharmonic motion of Si within the Ti3SiC2. The results presented could explain differences between calculated elastic moduli using DFT harmonic lattice dynamics simulations and results from recent experiments.展开更多
A series of YAG:Ce,Mn transparent ceramics were prepared via a solid-state reaction-vacuum sintering method.The effects of various Mn^2+–Si4+pair doping levels on the structure,transmittance,and luminescence properti...A series of YAG:Ce,Mn transparent ceramics were prepared via a solid-state reaction-vacuum sintering method.The effects of various Mn^2+–Si4+pair doping levels on the structure,transmittance,and luminescence properties were systematically investigated.These transparent ceramics have average grain sizes of 10–16μm,clean grain boundaries,and excellent transmittance up to 83.4%at 800 nm.Under the excitation of 460 nm,three obvious emission peaks appear at 533,590,and 745 nm,which can be assigned to the transition 5 d→4 f of Ce^3+and 4 T1→6 A1 of Mn^2+.Thus,the Mn^2+–Si4+pairs can effectively modulate the emission spectrum by compensating broad orange-red and red spectrum component to yield high quality warm white light.After the optimized YAG:Ce,Mn transparent ceramic packaged with blue light-emitting diode(LED)chips,correlated color temperature(CCT)as low as 3723 K and luminous efficiency(LE)as high as 96.54 lm/W were achieved,implying a very promising candidate for application in white light-emitting diodes(WLEDs)industry.展开更多
文摘For the first time detailed measurements of the DOS （density of states） for Ti3AIC2 and Ti3SiC2 are presented at temperatures between T = 10 and 100 K. For Ti3AIC2 a DFT （density functional theory） simulation of lattice dynamics is compared to experimental data demonstrating a noticeable difference between the spectra especially below 40 meV. In the case of Ti3SiC2 the DFT model is augmented with MD （molecular dynamics） simulations resulting in the measured and simulated spectra resembling one another more closely but still having significant differences below 40 meV. Within the experimental spectra, there are features up to and including 20 meV which are unaccounted for by the simulation. Tracing individual atoms generated by the computer models suggests anharmonic motion of Si within the Ti3SiC2. The results presented could explain differences between calculated elastic moduli using DFT harmonic lattice dynamics simulations and results from recent experiments.
基金the CAS Priority Research program(XDB20010300,XDA21010204)National Natural Science Foundation of China(201501178)Natural Science Foundation of Fujian Province(2017H0048)。
文摘A series of YAG:Ce,Mn transparent ceramics were prepared via a solid-state reaction-vacuum sintering method.The effects of various Mn^2+–Si4+pair doping levels on the structure,transmittance,and luminescence properties were systematically investigated.These transparent ceramics have average grain sizes of 10–16μm,clean grain boundaries,and excellent transmittance up to 83.4%at 800 nm.Under the excitation of 460 nm,three obvious emission peaks appear at 533,590,and 745 nm,which can be assigned to the transition 5 d→4 f of Ce^3+and 4 T1→6 A1 of Mn^2+.Thus,the Mn^2+–Si4+pairs can effectively modulate the emission spectrum by compensating broad orange-red and red spectrum component to yield high quality warm white light.After the optimized YAG:Ce,Mn transparent ceramic packaged with blue light-emitting diode(LED)chips,correlated color temperature(CCT)as low as 3723 K and luminous efficiency(LE)as high as 96.54 lm/W were achieved,implying a very promising candidate for application in white light-emitting diodes(WLEDs)industry.
