Narrow Results

The higher doping level Y_1-xCa_xBa_2-xLa_xCu₃O_y samples were synthesized with x from 0.25 to 0.55. Structure and superconductivity have been investigated. Comparing with the results of lower doping level, the T_c of these samples keeps almost constant when dopant increasing. While some structural characters, such as Cu(1)-O(4), Cu(2)-O(4) bond lengths change randomly in a narrow range. The relationship between Ba/La position and T_c is rather interesting. The results give another evidence that the influence of structural change on superconductivity is independent of carrier concentration.

The samples of Y_1-xSr_xBa_2-xLa_xCu₃O_y (YSBLCO) were synthesized and characterized by DC magnetization measurements and X-ray diffraction. The structures of the samples were refined by Rietveld method. Although the carrier concentration in the samples is constant at different dopant levels, the superconductivity evidently changes. We attribute decrease in Tc to a charge redistribution in the crystalline lattice. Comparing the change of the T_c value caused by structural influence and carrier concentration, it is suggested that the influence of structural changes on the superconductivity is independent of that induced by carrier concentration.

P-type (Al, N) co-doped ZnO films have been prepared by thermal oxidation of sputtered Zn₃N₂:Al precursor films. The Zn₃N₂:Al precursors are deposited by RF magnetron sputter and then annealed in oxygen atmosphere at different temperatures. The doped ZnO films are characterized by XRD, XPS and Hall effect measurement. The results indicate that the ZnO films only show p-type conductivity with an annealing in a temperature window: ZnO films show the best p-type characteristics with a hole concentration of 4.2 × 10¹⁷cm^-3, mobility of 0.52 cm/V.s and resistivity of 28Ωcm after an annealing at 550°C. Using these p-type ZnO films, ZnOp-n junctions are prepared which show good diode characteristics. The chemical states of N and Al dopants in the ZnO host material are investigated by XPS method after annealing at different temperatures; and the doping mechanisms are discussed based on the XPS results.

According to the first-principle method for the density functional theory (DFT), combined with the hybrid functional (HSE06), the electronic structure and effective mass of Mg-doped GaN and Mg–Fe co-doped GaN systems are calculated, and the stability of the co-doped structure is analyzed from the perspective of formation energy and phonon dispersion. The results showed that the introduction of Fe improved the characteristics of GaN:Mg system: the GaN material doped with Mg merely would cause the material’s valence band maximum to exceed the Fermi level, presenting a $p$-type conduction; the addition of Fe increased the energy band density of the system, and the insulation of the material was enhanced due to the higher energy level of the introduced impurity. Furthermore, the influence of Mg doping on the magnetic properties of GaN-based diluted magnetic semiconductor (DMS) was considered as well, with the magnetic moment obtained from co-doping Mg–Fe slightly reduced by a comparison of that of GaN:Fe measured by our research group. The results showed that the difference in the effective mass of GaN:Mg:Fe system in different directions was smaller than that of GaN:Mg system, indicating that the anisotropy of the system was reduced by doping Fe.

In this work, fabrication and investigation of substituing high-valence W⁶⁺ for Ti⁴⁺ ion on B-site of La³⁺-doped Bi₄Ti₃O₁₂ or BLT structure to form Bi_3.25La_0.75(Ti_1-xW_x)₃O₁₂ or BLTW (when x = 0, 0.01, 0.03, 0.05 0.07, 0.09 and 0.10) ceramics were carried out. X-ray diffraction patterns of BLTW ceramics indicated orthorhombic structure with lattice distortion, especially with higher concentration of WO₃ dopant. An increase in WO₃ doping content reduced not only length and thickness of grain, but also density of the ceramics. Electrical conductivity was found to decrease, while dielectric constant increased with W⁶⁺ doping. Ferroelectric properties were found to be improved with increasing WO₃ content and were optimized at x = 0.05.

By adopting density functional theory in combination with nonequilibrium Green's functions, we investigated the electronic structure and transport properties of silicon/nitrogen (Si/N) co-doping armchair graphene nanoribbons (AGNRs) with SiN_x co-dopant incorporated in neighboring carbon atoms. The results demonstrate that the electronic structure can be modulated by introducing SiN_x co-dopants in AGNRs. The striking negative differential resistance behaviors in the range of low bias can be observed in Si/N co-doped AGNR devices. These remarkable properties suggest the potential application of Si/N co-doping AGNRs in molectronics.

In this study, the WIEN2k code, utilizing the full potential linearized augmented plane wave (FPLAPW) approach within the framework of density functional theory (DFT), explicitly employing the PBEsol approximation, is employed to investigate the fundamental properties of W-doped and (Mo, W) co-doped cubic CeO₂. Herein, lattice constants, bulk modulus and cell volumes were evaluated for structural properties. The total density of states (TDOS) for various doped and co-doped CeO₂ systems was used to explain the origin of magnetic behavior. The band structure (BS) calculations show that the doped and co-doped materials exhibit semiconductor behavior with a direct bandgap in both spin channels. The calculated total spin magnetic moments of W/CeO₂ and (Mo, W)/CeO₂ alloys are 2.002${\mu }_B$ and 4.007${\mu }_{B,}$ respectively.

Furthermore, the optical absorption shows absorption peaks in the visible range and a redshift. As a result, adding molybdenum and tungsten additives improves the electro-optical properties of previous materials.

To explore the excellent sensor for detecting the pollution gas $S{O}_2$, the adsorptions of $S{O}_2$ molecule on the surfaces of Fe/Co-doped carbon nanotubes (CNTs) and single vacancy defected (8, 0) CNTs were investigated by using density functional theory (DFT). In addition, the adsorption energies, geometries, energy gaps and electronic structures were analyzed. The results showed that Fe/Co-doping and single-vacancy-defected can improve the adsorption and sensitiveness of CNTs toward $S{O}_2$. Considering the changes of energy gap before and after the $S{O}_2$ molecule adsorbed on each modified CNTs and its adsorption strength, Fe-doped CNTs (Fe-CNTs) and Co-doped site-2 single-vacancy-defected CNTs performed better for detecting $S{O}_2$ molecule. With the decreasing number of electrons of the doped atom (Fe, Co, Ni), the adsorption became more stable. The results of this paper are profound and meaningful for designing $S{O}_2$ sensing devices.

The layered material of nickel cobalt manganese oxide lithium oxide is one of the most promising lithium-ion battery (LIBs) materials, with the characteristics of high capacity and high density. However, most nickel-rich layered oxides have the phenomenon of cation mixing and the phenomenon that the layered structure changes to the spinel structure during the cycle, which results in poor capacity and cycle performance under high cut-off voltage. Herein, we modified LiNi${}_{0.5}$Co${}_{0.2}$Mn${}_{0.3}$O₂ with Ti and Na co-doping to observe the changes in the specific capacity, cycle performance and crystal structure of the material. Ti and Na co-doped LiNi${}_{0.5}$Co${}_{0.2}$Mn${}_{0.3}$O₂ has the most obvious effect on increasing the discharge specific capacity and improving the cycle performance. In sthe voltage range of 3–4.5V, its discharge specific capacity reaches 183.5mAh/gat 0.5C, and the capacity retention rate after 100 cycles is 81.96%, and its discharge specific capacity reaches 164.2mAh/g at 1C and after 100 cycles Capacity retention rate is 80.93%. The introduction of Ti and Na plays an important role in improving the cation mixing phenomenon and improving the stability of the crystal structure.

Bi_(1.98-x)In_0.02Na_xTe_2.7Se_0.3 (x = 0, 0.02, 0.04, 0.06) and Bi₂Te_2.7Se_0.3 alloys were prepared by vacuum melting and hot pressing methods. The phase structure of the bulk samples were characterized by X-ray diffraction. Effects of indium and sodium co-substitutions for bismuth on the electrical and thermal transport properties were investigated in the temperature range of 298–473 K. Indium and sodium co-doping can enhance the carrier concentration, and accordingly the electrical conductivity can be improved effectively. The Seebeck coefficients of the co-doped samples have not been derogated strongly. The power factors are enhanced for the Bi_(1.98-x)In_0.02Na_xTe_2.7Se_0.3 (x = 0.02) within the whole testing temperature range. The Bi_(1.98-x)In_0.02Na_xTe_2.7Se_0.3 (x = 0.02) samples have the lower thermal conductivity due to reduction in lattice thermal conductivity, which leads to a great improvement in the thermoelectric figure of merit ZT. The highest ZT of the sample can reach 0.87 at 398 K.

Translucent alumina doped with ZrO₂ and MgO was fabricated by two-step vacuum sintering (1475${}^{\circ }$C/30min followed by 1320${}^{\circ }$C/20min) with a high heating rate (80${}^{\circ }$C/min). Densification, grain size, phase composition, mechanical properties and translucency of the alumina were investigated. The results indicated that co-doping of ZrO₂ and MgO showed a synergetic effect on grain refinement and densification process. On one hand, the solubility of MgO in alumina was increased by the ZrO₂ additive, which was favorable for the densification. On the other hand, more favorable ZrO₂ accommodation sites existed at the alumina grain boundaries created by the MgO, effectively decreasing the grain size. Finally, the sample with porosity of 0.5% and mean grain size of 1.21$\mu$m was obtained at a co-doped content of 0.35wt.% of ZrO₂ and MgO (mass ratio of 1:1). The co-dopants led to the enhanced hardness and bending strength as well as a favorable fracture toughness of the translucent alumina, when compared with the MgO single-doped and doping free samples. Moreover, total transmission of as high as 51% and good translucency was also obtained. The improved properties widened the prospect of the translucent alumina used as dental restorative materials.

La₂Mo₂O₉ doped with cheap metal cations can further increase their conductivity. The transition metal element Mn and the rare-earth element Y co-doped La₂Mo₂O₉-based electrolyte was used, and the sintered ceramic body La${}_{1.9}$Y${}_{0.1}$Mo ${}_{2-}$${}_x$Mn${}_x$O ${}_{9-}$${}_{\delta }$($x$= 0$\sim$0.4) was prepared by the sol-gel method, sintering at 950°C. The results show that the samples can suppress the phase transition and retain the $\beta$-phase of the structure of La₂Mo₂O₉, due to doping, and it is a single pure phase, which has good sintering performance. Among them, La${}_{1.9}$Y ${}_{0.1}$Mo${}_{1.8}$Mn${}_{0.2}$O${}_{8.8}$ reached the maximum ionic conductivity of 0.0292 S⋅cm${}^{-1}$ at 800°C, and Ea is 0.425 eV, which can become a solid electrolyte material of IT-SOFC.

Nd/Pr co-doped ${\mathrm{\text{Bi}}}_2{\mathrm{\text{WO}}}_6$ photocatalytic materials were prepared via a simple one-step hydrothermal method. The physicochemical properties of the prepared samples were characterized by XRD, Raman, UV-Vis DRS, PL, SEM, BET analysis and photocatalytic tests. The results showed the co-dopants of Nd and Pr ions with the concentration of 1% Nd and 1% Pr exhibited the highest photocatalytic activity. Rhodamine B (RhB) was almost completely degraded within only 10 min. The increased photocatalytic activity on the co-doped ${\mathrm{\text{Bi}}}_2{\mathrm{\text{WO}}}_6$ is attributed to the increasing specific surface area, the inhibited recombination of photogenerated carriers and the reduced band gap energy. This study provides a helpful strategy for developing effective photocatalysts.

Dielectrics with high permittivity and temperature stability are important for the development of high-temperature multilayer ceramic capacitors (MLCCs). In this study, Ca${}_{1-x}$Na_xTi${}_{1-x}$Nb_xSiO₅ (abbreviated as CTS$-x$NN) ceramics were prepared by solid-phase reaction method. The introduction of NN weakens the long-range ordered displacement of Ti, leading to a significant increase in the dielectric temperature stability. The CTS−2%NN samples exhibit high permittivity (53) and TCC $\le \pm 170$ ppm/^∘C in the range of $-55^{\circ }$C to 300^∘C. The CTS-based ceramics behave high dielectric temperature stability. In addition, the bandgap of the CTS-based ceramics increased significantly, which is favorable for improving the breakdown strength of the material. For $x=4$% samples, the breakdown strength reaches 621kV/cm. Thus, the designed CTS-based dielectrics are promising for high-temperature capacitors.