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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.