450
A. Das
them in technological applications. Among the synthesis procedures, the sol–gel
process is advantageous for its low cost, simple method, and production of high
purity, size-controlled nanoparticles. The fabrication of three different CdO samples
was achieved by sol–gel method followed by annealing in 400, 450, and 500 °C to
obtain various crystallite sizes. The size, crystal structure, and morphology of the
samples are discussed. Positron annihilation spectroscopy has been carried out to
defect characterization and to closely observe the core electron structure with the
changes in particle size.
2 Experimental Details: Synthesis of Samples
Two different solutions were prepared by dissolving 0.1 M CdCl 2 and 0.1 M NaOH
in 40 ml and 200 ml distilled water. Another mixture of ethylene glycol and methanol
was prepared in 1:2 ratio. Ethylene glycol mixture was added to NaOH solution and
stirred for 1 h. Then CdCl 2 solution was added and stirred for 2 h. A milky white solution was obtained. The precipitate was formed by adding acetone to it. The precipitate
was washed by methanol and heated to 70 °C to evaporate the methanol. Then the
dried precipitate was annealed in a furnace at 300 °C. By changing the concentration
of ethylene glycol, two other samples of different particle sizes were prepared. X-ray
diffraction (XRD) patterns of the samples were recorded with Bruker D8 Advance
diffractometer using Cu Kα (λ = 1.5406 Å) radiation at 40 kV and 40 mA. All
the samples were scanned from 20° to 85° with a scanning speed of 2° (2θ ) per
minute. HRTEM images were taken with a JEOL (Model JEM 2200FS) microscope
operating at 200 kV. To carry the Coincidence Doppler-Broadening measurements, a
10 μCi strong
22 Na source was used. The source was kept immersed inside a column
of powdered sample taken in a glass tube. The source and sample were kept in
a moisture-free condition. Coincidence Doppler-Broadening (CDB) measurements
were done with two high-purity germanium detectors (HPGe) of energy resolutions
1.33 keV and 1.27 keV at 0.511 meV. Analysis was done with AMPS (Chatterjee
et al. 2013). About 2.0 × 10
7 coincidence events were accumulated under CDB
spectrum.
2.1 Result of X-Ray Diffraction Spectroscopy
Figure 1 shows the XRD patterns of three CdO nanoparticulate samples. Our peaks
agree well with the standard values (JCPDS Card No. 05-0640) from which the purity
of the samples is confirmed and face-centered cubic structure is clearly seen. The
lattice constant of bulk CdO is 4.77 Å (Yao et al. 2013). From the XRD data, we
have measured the lattice constant of each sample. From the most intense broadened
peak width, the average crystallite sizes of the different samples were estimated by
A. Das
them in technological applications. Among the synthesis procedures, the sol–gel
process is advantageous for its low cost, simple method, and production of high
purity, size-controlled nanoparticles. The fabrication of three different CdO samples
was achieved by sol–gel method followed by annealing in 400, 450, and 500 °C to
obtain various crystallite sizes. The size, crystal structure, and morphology of the
samples are discussed. Positron annihilation spectroscopy has been carried out to
defect characterization and to closely observe the core electron structure with the
changes in particle size.
2 Experimental Details: Synthesis of Samples
Two different solutions were prepared by dissolving 0.1 M CdCl 2 and 0.1 M NaOH
in 40 ml and 200 ml distilled water. Another mixture of ethylene glycol and methanol
was prepared in 1:2 ratio. Ethylene glycol mixture was added to NaOH solution and
stirred for 1 h. Then CdCl 2 solution was added and stirred for 2 h. A milky white solution was obtained. The precipitate was formed by adding acetone to it. The precipitate
was washed by methanol and heated to 70 °C to evaporate the methanol. Then the
dried precipitate was annealed in a furnace at 300 °C. By changing the concentration
of ethylene glycol, two other samples of different particle sizes were prepared. X-ray
diffraction (XRD) patterns of the samples were recorded with Bruker D8 Advance
diffractometer using Cu Kα (λ = 1.5406 Å) radiation at 40 kV and 40 mA. All
the samples were scanned from 20° to 85° with a scanning speed of 2° (2θ ) per
minute. HRTEM images were taken with a JEOL (Model JEM 2200FS) microscope
operating at 200 kV. To carry the Coincidence Doppler-Broadening measurements, a
10 μCi strong
22 Na source was used. The source was kept immersed inside a column
of powdered sample taken in a glass tube. The source and sample were kept in
a moisture-free condition. Coincidence Doppler-Broadening (CDB) measurements
were done with two high-purity germanium detectors (HPGe) of energy resolutions
1.33 keV and 1.27 keV at 0.511 meV. Analysis was done with AMPS (Chatterjee
et al. 2013). About 2.0 × 10
7 coincidence events were accumulated under CDB
spectrum.
2.1 Result of X-Ray Diffraction Spectroscopy
Figure 1 shows the XRD patterns of three CdO nanoparticulate samples. Our peaks
agree well with the standard values (JCPDS Card No. 05-0640) from which the purity
of the samples is confirmed and face-centered cubic structure is clearly seen. The
lattice constant of bulk CdO is 4.77 Å (Yao et al. 2013). From the XRD data, we
have measured the lattice constant of each sample. From the most intense broadened
peak width, the average crystallite sizes of the different samples were estimated by