BiNbO4 has stirred up great deal of interest due to its excellent photocatalytic activities. Besides, it possesses rich polymorphism. Here, the structure stability and structural evolution of orthorhombic α- and...
Eu3+ ions doped bismuth vanadate powders were synthesized
by a hydrothermal method, and the effect of Eu3+ ions doping
on the crystal structure was investigated by X-ray diffraction (XRD),
Raman, and UV–vis diffuse reflectance spectra. XRD and Raman
results reveal that the doping solubility of Eu3+ ions
in fergusonite-BiVO4 is extremely small. Above 0.5 mol
% doping, a structural transition from fergusonite to zircon structure
occurs. This phase transition results in band gap enhancement and
thus limits its photocatalytic performance. Upon compression, zircon-BiVO4:Eu3+ is not stable, and a zircon-to-scheelite
transition presents above 5 GPa. It is noted that this transition
is irreversible, and the high-pressure scheelite structure transforms
back to the fergusonite structure rather than the original zircon
structure after pressure release. The transition sequence of zircon-to-scheelite-to-fergusonite
in a compression-decompression cycle for BiVO4:Eu3+ provides one method to synthesize fergusonite-BiVO4:Eu3+ with more doping content. This result confirms that pressure
is one effective strategy to access new structures and novel physical
properties of functional material.
Er3+/Yb3+ co-doped InNbO4 phosphors were synthesized using solid state reaction method. Crystal structure was characterized using X-ray diffraction (XRD), which confirm all obtained phosphors had a monoclinic-wolframite structure and no impurity phase
was introduced upon doping. Upon 980 nm excitation, upconversion (UC) emission from Er3+ ions was observed in green and red range. UC emission was obviously enhanced after co-doping Yb3+ ions and reached the maximum for 10 mol% Yb3+ ions. The relation between
emission intensity and pump power was performed, revealing that the UC emission result from two-photon processes. Optical temperature sensing property was investigated by exploiting fluorescence intensity ratio (FIR) between 2H11/2 and 4S3/2 levels
of Er3+ ions. Its maximum value of absolute sensitivity obtained was 0.0091 K-1, suggesting InNbO4:Er3+/Yb3+ phosphors show potential application in optical thermometry.
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