Melting-solidification transition of Zn nanoparticles embedded in SiO2: Observation by synchrotron x-ray and ultraviolet-visible-near-infrared light
Abstract
Melting-solidification transition of Zn nanoparticles (NPs) with the mean diameter of 11.5 nm, embedded in silica glass, was investigated by glancing incident x-ray diffraction (GIXRD) at high temperatures using synchrotron radiation (SR). With increasing temperature, 101Zn diffraction peak gradually decreases up to ∼360 °C and then steeply decreases. This is due to the melting of Zn NPs, which completes around 420 °C. With decreasing temperature, the solidification of the NPs begins around ∼310 °C. The temperature hysteresis with a width of ∼110 °C was observed. With temperature, the diffraction angle shows a shift without hysteresis, which is ascribed to thermal expansion of Zn NP lattice. Thermal expansion coefficient of Zn NPs was determined as 24.4×10-6 K-1 along the ⟨101⟩ direction. Optical absorption spectroscopy shows a broad ultraviolet (UV) peak which was observed at even higher temperatures than the melting temperature but shifts to the low-energy side with the melting. The energy shift in the UV peak also shows the temperature hysteresis which resembles with the melting-solidification hysteresis recorded by SR-GIXRD. The melting-solidification transition is also detectable by the optical absorption spectroscopy in the UV-visible-near-infrared region.
- Publication:
-
Journal of Applied Physics
- Pub Date:
- November 2010
- DOI:
- 10.1063/1.3494098
- Bibcode:
- 2010JAP...108j4302A
- Keywords:
-
- infrared spectra;
- melting;
- nanoparticles;
- silicon compounds;
- solidification;
- synchrotron radiation;
- thermal expansion;
- ultraviolet spectra;
- visible spectra;
- X-ray diffraction;
- zinc;
- 61.46.Df;
- 81.30.Fb;
- 64.70.dj;
- 78.67.Bf;
- 78.40.Kc;
- 78.30.Er;
- Nanoparticles;
- Solidification;
- Melting of specific substances;
- Nanocrystals and nanoparticles;
- Metals semimetals and alloys;
- Solid metals and alloys