Page 121 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Yttrium Oxide Nanoparticles Synthesis - a Model Study on the Plasma-Liquid Interaction and Opener to Nanophosphors
nm at 600 °C to 10-40 nm at 800 °C, 15-50 nm at 1000 °C and 30-80 nm at 1200 °C, indicating that flexible control of size can be achieved by simply adjusting the calcination temperature.
Typical high-magnification TEM image and representative selected area electron diffraction pattern of the Y2O3 nanoparticles are also provided in Figure 6.7. Lattice fringes corresponding to the (211) and (222) planes of the cubic Y2O3 nanoparticles are shown in the HRTEM image, suggesting their polycrystalline nature. Besides, the SAED pattern also indicates the high crystalline nature of the synthesized products, and the spots are well indexed to (211), (222), (431) and (440) planes of cubic Y2O3 nanoparticles (JCPDS card #41-1105).
Figure 6.7 Representative HRTEM image (a) and SAED pattern (b) of the synthesized Y2O3 nanoparticles
The XRD patterns of Y2O3 nanoparticles annealed at various temperatures are shown in Figure 6.8. Meanwhile, the JCPDS card #41-1105 for cubic Y2O3 is also provided as a reference. It is clearly observed that these diffraction peaks match perfectly with the JCPDS card, providing additional validation for the assertion that cubic Y2O3 nanoparticles are formed. Among them three characteristic peaks at 2θ values of 29.2◦, 48.5◦ and 57.6◦ are indexed to (222), (440) and (622) crystal planes, and minor peaks of cubic Y2O3 nanoparticles at 20.5◦ (211), 33.8◦ (400), 35.9◦ (411), 39.8◦ (332), 43.5◦ (431), 53.2◦ (611) and 59.0◦ (631) are also shown.26,27 The narrowing of the peaks with calcination temperatures reflects improved crystallinity as well as increased grain size, in agreement with the TEM results. The average crystallite size of Y2O3 nanoparticles is estimated from the highest peak (222) using the Scherrer formula: d = K λ βcosθ
Where K is the so-called shape factor (0.9), λ is the used wavelength of the X-ray source (1.54056 Å), β is the line broadening at half the maximum intensity, and θ is the Bragg angle of the peak (111). The calculated values are 10.9 nm, 16.8 nm, 29.7 nm and 46.5 nm at calcination temperature of 600 °C, 800 °C, 1000 °C and 1200 °C respectively.
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