Fengnian Zhang,Fuhao Cheng,Chufei Cheng,Meng Guo,Yufeng Liu,Yang Miao,Feng Gao,Xiaomin Wang
Abatract A series of compositionally complex fluorite oxides (CCFOs) were prepared by ball milling the mixture of ZrO 2 , HfO 2 , Y 2 O 3 , La 2 O 3 , and Pr 6 O 11 followed by conventional solid-state sintering. Both XRD and TG-DSC results demonstrated that single-phase (Zr 0.2 Hf 0.2 Pr 0.2 Y 0.2 La 0.2 )O 2-δ was formed at 1400 °C. Elements in bulk ceramic were uniformly distributed without evident accumulation according to SEM-EDS pictures. TEM results revealed that polycrystalline ceramic powder was assignable to cubic Fm-3m fluorite structure. The electrical conductivity ( σ ) was measured via EIS technology and activation energy ( E a ) of CCFOs was calculated in Arrhenius plots. In the temperature range of 300-750 °C, CCFOs preserved the same conduction mechanism and (Zr 0.1667 Hf 0.1667 Pr 0.1667 Y 0.25 La 0.25 )O 2-δ possessed higher σ and lower E a than other high entropy fluorite oxides which is related to the incorporation of Pr element or the connection of cation-V o complex.
CAO RENPING,QIN ZHENGDONG,JIANG SHENHUA,LIANG AIHUI,LUO ZHIYANG,YU XIAOGUANG
A series of CaNb 2 O 6 : x Sm 3+ (0 ≤
x
≤ 10 mol%) and CaNb 2 O 6 : Sm 3+ , Na + /B 3+ phosphors were synthesized by the solid-state reaction method in air. Their crystal structures and luminescence properties were investigated and analysed, respectively. Host CaNb 2 O 6 emitted blue light with excitation 270 nm. CaNb 2 O 6 : x Sm 3+ phosphors showed a systematically varied hue from blue to white by changing Sm 3+ ion concentration from 0 to 10 mol% with excitation of 270 nm and their chromaticity coordinates were the regions from (0.1665, 0.1767) to (0.2484, 0.2260). Luminescence properties of CaNb 2 O 6 : Sm 3+ phosphor were tuned and improved significantly by codoping B 3+ or Na + ions. Energy transfer between Nb \(_{\mathbf {2}}\textit {O}_{\mathbf {6}}^{\boldsymbol {2-}}\) group and Sm 3+ ion was observed and analysed via luminescence properties. The luminous mechanism was explained by energy level scheme and energy transfer process in CaNb 2 O 6 : Sm 3+ phosphor. The strong excitation band peaking at ∼ 407 nm indicated that the CaNb 2 O 6 : Sm 3+ , Na + /B 3+ phosphor has a potential application in white light-emitting diodes based on near-UV LED chip.
Al 2 O 3 : Er 3+ /Yb 3+ transparent ceramics codoped with Zn 2+ ions with intense upconversion and near infrared emission were prepared by conventional solid-state reaction and vacuum and hot isostatic pressing sintering. The effects of Zn 2+ incorporation to the structure, transparent, upconversion and NIR luminescence were discussed in detail. The as prepared Al 2 O 3 ceramics exhibited a total transmittance of ~ 75% in infrared regions (800–3300 nm) and ~ 50% in visible regions (500–800 nm). Under the excitation of a 980 nm laser diode , the as prepared Al 2 O 3 ceramics displayed two tense upconversion emission peaks of a green one centered at 550 nm and a red one centered at 660 nm and a tense near infrared emission peak centered at 1.532 µm, characteristic of Er 3+ emission. Compared with Er 3+ /Yb 3+ doped only, Zn 2+ codoped Al 2 O 3 :Er 3+ /Yb 3+ transparent ceramics showed higher upconversion and near infrared emission of ~ 11 times and ~ 4 times, respectively. The enhancement mechanism due to incorporation of Zn 2+ ions was also discussed in detail.
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