Structural, morphological and luminescence properties of nanocrystalline up-converting Y1.89Yb0.1Er0.01O3 phosphor particles synthesized through aerosol route

Nanocrystalline up-converting Y₂ O₃Yb³⁺ Er³⁺ phosphor particles were processed in a dispersed system-aerosol, generated ultrasonically at 1.3 MHz from common nitrate precursor solution having fixed ytterbium-to-erbium concentration ratio. The appropriate process parameters: residence time 21 s, carrier gas (air) flow rate 1.6 dm3/min, synthesis temperature 900 °C, led to the formation of un-agglomerated spherical nanostructured secondary particles, having mean particle size of approx 450 nm, composed of primary nanoscaled (20 nm) subunits. In order to reach targeting phase crystallinity, the as-prepared particles were additionally annealed at 1100 °C in air for 12, 24 and 48 h, respectively. Particle structure, morphology and purity were analyzed by X-ray powder diffraction (XRPD), scanning electron microscopy (FESEM/SEM), analytical and high resolution transmission electron microscopy (TEM/HRTEM) in combination with energy dispersive X-ray analysis and Fourier Transform Infrared Spectroscopy (FTIR). All samples crystallized in a cubic bixbyte-structure, space group Ia-3. The crystallite size changed with annealing time from 30 nm in as-prepared sample to 135 nm in sample annealed for 48 h, respectively. Emission spectra were assigned to the following trivalent erbium f–f electronic transitions: ²H₉/₂ → ⁴I₁₅/₂ (blue: 407–420 nm), (²H₁₁/₂̦ ⁴S₃/₂) → ⁴I₁₅/₂ (green: 510–590 nm), and ⁴F₉/₂ → ⁴I₁₅/₂ (red: 640–720 nm). The significant improvement of the emission decay times were observed after thermal treatment and this effect is correlated further with the structural and morphological particles characteristics. For the anneal-ing time of 12 h a quite high emission decay times were achieved (blue: 0.14 ms, green: 0.32 ms and red: 0.39 ms).This research is financially supported through the Project #172035 of the Ministry of Science and Education of the Republic of Serbia. OM especially acknowledge the University Carlos III, Madrid, Spain-Santander Bank Chairs of Excellence program and JSPS 2011/2012 fellowship, Japan.Publicad

Nanostructured (Y1-Xgdx)(2)O-3:Eu3+ Powders Obtained Through Aerosol Synthesis

In this study, nanophase, spherical, polycrystalline (Y1-xGdx)(2)O-3:Eu3+ phosphor particles were synthesized from aerosols of corresponding nitrate solutions, ultrasonically generated at 1.3 MHz frequency, and thermally decomposed at 900 and 1100 degrees C. Structural and morphological analyses done by X-ray powder diffraction (XRPD) and transmission electron microscopy analysis (TEM) implied the formation of non-aggregated spherical, submicronic particles with smooth particle surfaces and filled morphology. The phase development and structural changes, determined using the Topas program, implied a nanocrystalline inner structure (crystallites LT 20 nm), that was also confirmed by SAED analysis. A bcc Ia-3 cubic phase was identified in all as-prepared samples, apart from the mixed oxide with the gadolinium content GT 75%, where the existence of a secondary, fcc Fm-3m cubic phase is determined. Only Ia-3 cubic phase was identified in thermally treated samples (1100 degrees C), while the powder morphological features were maintained, followed by increase in powder crystallinity and phase homogeneity. Functional properties were analyzed by means of photoluminescent analysis. Emission spectra showed typical Eu3+ D-5(0) - GT (7)Fi (i = 0, 1, 2, 3, 4) transitions with the dominant red emission peak at 611 nm.Ceramic Transactions, 3rd International Conference on Characterization and Control of Interfaces for High Quality Advanced Materials, 2009, Kurashiki, Japa