Phase Transition and High Piezoactivity of Sb Doped （Na0.53K0.435Li0.035）Nb0.94Ta0.06 O3 Lead-Free Ceramics

Lead-free piezoelectric ceramics with the composition of （Na0.53K0.435Li0.035）Nb0.94Ta0.06 O3 （NKLNST） axe synthesized by a conventional solid-state sintering process. An MPB-like region between orthorhombic and pseudocubic phases is found in this system. The density, piezoelectric and dielectric properties axe enhanced greatly in this region. A composition （Na0.53K0.435Li0.035）（Nb0.94Ta0.06）O3 is found to have excellent electrical properties： d33 = 320pC/N, kp= 49% and kt =43%, as well as relatively low loss, tan δ=4.2%, and high relative density higher than 96%, which indicate that this ceramics is a promising lead-free piezoceramics replacing for lead zirconate titanate.     

Surface modification of silicon with single ion irradiation

In order to solve the issues in Si nanoelectronics such as fluctuation in the device functions and poor reliability of devices due to relative increase in mass transport in nm size structures and to yield novel functions by rather taking advantage of the nm size, we need to understand the phenomena peculiar to nm size structures. Based on the fact that a practical method to fabricate nm structures in terms of throughput, process time, and cost is to combine modification of solid surfaces with energetic particles (especially with single ions) and subsequent chemical processing in solutions, we describe single ion irradiation effects as a tool to modify solid surfaces in nm scale, a method for nm scale in-situ observation of solid surfaces, and some examples of the acquired knowledge.     

Enhanced luminescence of GdTaO4:Eu thin-film phosphors by K doping

The effect of K⁺ ions on GdTaO₄:Eu³⁺ thin-film phosphors was investigated in order to improve their luminescent properties. The GdTaO₄:Eu_0.1, K_x thin films were synthesized by sol-gel process, and characterized through measuring their microstructure and luminescence. The results indicated that photoluminescence (PL) intensity of GdTaO₄:Eu³⁺ film was improved remarkably by K doping. There were two maxima in the curve of PL intensity against K⁺ dopant concentration, where one was improved up to 2.1 times at x = 0.001 and the other was enhanced up to 2.7 times at x = 0.05. The first maximum was regarded as the alteration of the local environment surrounding the Eu³⁺ activator by incorporation of K⁺ ions, and the second maximum was due to the flux effect. Additionally, the luminescence increased with the increase of firing temperature from 800 °C to 1200 °C.     

Ti deficiency effect on the dielectric response of CaCu3Ti4O12 ceramics

Single phase ceramics CaCu₃Ti_4.0O₁₂ and CaCu₃Ti_3.9O₁₂ have been prepared using the traditional solid-state reaction method. Compared with the stoichiometric ceramics CaCu₃Ti_4.0O₁₂, Ti-deficient ceramics CaCu₃Ti_3.9O₁₂ have the larger lattice parameter, the higher force constant, and smaller dielectric constant and the lower dissipation factor, although their fundamental characters of dielectric response are similar. Their characteristic relaxation frequencies are not well fitted with the Arrhenius Law but a tentatively supposed relation. With the Cole-Cole Law, the fitted broadened factors of dissipation peaks are 0.5433 and 0.8651 for CaCu₃Ti_3.9O₁₂ and CaCu₃Ti_4.0O₁₂, respectively. All facts mentioned above imply that mutually correlated motion of Ti ions or defects may be expected to be responsible for the giant dielectric constant and high dissipation factor of CaCu₃Ti_4.0O₁₂.     

Effects of sintering temperature and atmosphere on magnetism in Mn-doped TiO2 bulk samples

Magnetic properties have been investigated on Mn doped TiO₂(Ti_0.98Mn_0.02O₂) bulk samples prepared by solid state reaction, which were sintered at different temperature ranging from 450 ^°C to 900 ^°C in air and argon atmosphere, respectively. The results show that the magnetic properties were strongly dependent on the sintering temperature and atmosphere. For samples sintered in air, the magnetization initially increase with the increase of sintering temperature up to 600 ^°C and thereafter it decrease. While the magnetization of samples sintered in argon atmosphere decreases monotonically with the increase of sintering temperature. Furthermore, for samples sintered at 600 ^°C in air, the magnetic susceptibility exhibits a dominant Curie-Weiss behaviour and no magnetic transition is observed over the temperature range from 10 to 300 K. In contrast, for samples sintered in argon atmosphere, besides the magnetic transition near 45 K perhaps caused by Mn₃O₄, another magnetic transition appears near room temperature.     

Fabrication and properties of PLT/PLZT/PLT structures obtained by RF magnetron sputtering

Ferroelectric Pb_0.84La_0.16Ti_0.96O₃/Pb_0.96La_0.04(Zr_0.52Ti_0.48)_0.99O₃/Pb_0.84La_0.16Ti_0.96O₃ (PLT/PLZT/PLT) structures were fabricated on platinum-coated silicon wafers by RF magnetron sputtering. A Pb_0.84La_0.16Ti_0.96O₃ layer was used as a seed layer to improve the crystallization and enhance the ferroelectric properties of the PLZT film. With the PLT seed layers, the films showed excellent ferroelectric properties in terms of large remnant polarization (2P_r) of 52.7 μC/cm², lower coercive field (2E_c) of 130 kV/cm for an applied field of 500 kV/cm. Moreover, the PLT/PLZT/PLT structures exhibited good fatigue endurance after 10¹⁰ switching cycles, which was attributed to the double-sided PLT layers. They improved the electrical fatigue by eliminating the pyrochlore phase, reduced the strong (111) orientation, and assimilated the oxygen vacancies from the PLZT layer.     

Curve forecasting by functional autoregression

This paper deals with the prediction of curve-valued autoregression processes. It develops a novel technique, predictive factor decomposition, for the estimation of the autoregression operator. The technique is based on finding a reduced-rank approximation to the autoregression operator that minimizes the expected squared norm of the prediction error.Implementing this idea, we relate the operator approximation problem to the singular value decomposition of a combination of cross-covariance and covariance operators. We develop an estimation method based on regularization of the empirical counterpart of this singular value decomposition, prove its consistency and evaluate convergence rates.The method is illustrated by an example of the term structure of the Eurodollar futures rates. In the sample corresponding to the period of normal growth, the predictive factor technique outperforms the principal components method and performs on a par with custom-designed prediction methods.     

Ultraviolet and blue NaHg and NaCd excimer bands

We present the current-reversal spectra of the high pressure Na-Hg-Xe and Na-Cd-Xe lamps, from which the specific NaHg and NaCd structured continua have been observed. Detailed analysis revealed the existence of additional structure in the case of NaCd and NaHg blue diffuse bands. In the NaHg case the neighbourhood of the 330 nm sodium line revealed two satellite bands of NaHg origin, but almost no structure around the 330 nm sodium atomic line was found in the case of Na-Cd-Xe discharge lamp.     

The generalized uncertainty principle in (A)dS space and the modification of Hawking temperature from the minimal length

Recently, the Heisenberg's uncertainty principle has been extended to incorporate the existence of a large (cut-off) length scale in de Sitter or anti-de Sitter space, and the Hawking temperatures of the Schwarzshild–(anti) de Sitter black holes have been reproduced by using the extended uncertainty principle. I generalize the extended uncertainty to the case with an absolute minimum length and compute its modification to the Hawking temperature. I obtain a general trend that the generalized uncertainty principle due to the absolute minimum length “always” increases the Hawking temperature, implying “faster” decay, which is in conformity with the result in the asymptotically flat space. I also revisit the black hole-string phase transition, in the context of the generalized uncertainty principle.     

Dy~(3+):ThO_2的选择激发光谱和能级结构

本文首次用熔融法生长了Dy3 + :ThO2 晶体 ,详细研究了其光谱特性。通过 12K下格位选择激发下的发射光谱测量 ,利用晶场理论 ,确定了Dy3 + 在ThO2 中的格位对称性为C3v。列表给出了Dy3 + :ThO2 的晶场能级结构。测量和讨论了 4 F9/ 2 能级的寿命。