Production, characterization, and luminescent properties of Eu3+ doped yttrium niobate-tantalate films

Monoclinic yttrium tantalate (M'-YTaO4,M'-YTO),and two different kinds of yttrium niobium-tantalate (M'-YTao.85Nbo.15O4 (M'-YTNO) and Eu3+ doped M'-YTao.85Nbo.15O4 (M'-YTNO∶Eu3+)) were produced by sol-gel method and grown on single crystalline Si (100) substrate by spin coating approach.Structural properties and thermal behaviours of the films were characterized by means of X-ray diffraction (XRD),atomic force microscopy (AFM),scanning electron microscopy (SEM),and thermogravimetry and differential thermal analysis (TG-DTA).Systematic Steady-state photoluminescence and lifetime measurements in a series of yttrium niobium-tantalate with varying amounts of Eu3+ were presented.The photoluminescence spectra of the films exhibited strong blue (380-400 nm) and red (614 nm) emissions upon ultraviolet excitation.Emission intensities were strongly dependent on the host lattice composition and film morphology.1.5％ Eu3+ doped films exhibited the brightest luminescence and long lifetime extending to 1.22 ms when excited at 254 nm.To the best of our knowledge,this is the first attempt in the production of M'-YTO,M'-YTNO,and M'-YTNO∶Eu3+ films on single crystalline Si (100) substrate via sol-gel spin coating.

Thermal properties of Y1-xMgxTaO4-x/2 ceramics via anion sublattice adjustment

A systematic investigation concerned with Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20,respectively)ceramics was fabricated by a solid-state reaction method and characterized by X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM)and thermal analysis.XRD spectra display that all of the samples are excellently consistent with the standard XRD spectrum of monoclinic YTaO4(PDF No.24-1415;space group:I2(5)).The Raman peaks of the samples doped with Mg2+just widen slightly compared with those of pure YTaO4,which are in agreement with the results of XRD.The thermal conductivity of dense 7 wt%–8 wt%yttria-stabilized zirconia(7–8 YSZ)ceramic is about 2.5 W·m-1·K-1at 900°C,while the Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20)ceramics possess lower thermal conductivity in the range of 1.45–1.57 W·m-1·K-1at 900°C,which declines by35%compared with that of 7–8 YSZ.The lower thermal conductivities of Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16and 0.20)ceramics are originated from the enhanced phonon scattering caused by oxygen vacancy and Mg2+ions defect complex.However,the thermal expansion coefficients are about 9.0910-6–9.5910-6K-1along with the different amounts of Mg2+doping at 1200°C.Compared to the pure sample,the thermal expansion coefficient decreases slightly when the Mg2+doping amount is over 20%.The systematic investigations on the phase,microstructure,elastic and thermal properties of Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20)ceramics will provide guidance for its application at high temperature,especially as thermal barrier coatings.