CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

crystallinity. Thus, it was considered worthwhile to investigate the role played by lanthanide
ions on the structural changes and associated stability of GaOOH nanorods. Hence, detailed
structural and morphological investigations have been carried out on the samples and the
results are described below.
Figure 22 shows SEM images of GaOOH samples prepared in the presence of
different concentrations of Eu 3+ ions. GaOOH sample prepared in the absence of Eu 3+ ions
showed rod like morphology (Fig.22 (a)). The rods have length around 2.5-3 μm and width
around 300-400 nm. Similar rod like morphology has also been reported earlier for GaOOH
samples prepared either by urea hydrolysis or by hydrothermal synthesis [56, 171, 182]. For
GaOOH sample prepared in the presence of 0.5 at % Eu 3+ ions, the nanorods have length
around 1.5 to 2μm and width around 200-300 nm (Fig.22 (b)). However when the GaOOH
sample is prepared in the presence of 1.0 at % Eu 3+ ions, along with nanorods a significantly
aggregated/ agglomerated phase (with irregular shape) is also formed as is evident from the
SEM image (Fig.22 (c)). The nanorods have size in the range of 0.5-2 μm and width around
200 nm. No nanorod formation is observed for samples containing more than 1 at % Eu 3+
ions, instead an aggregated bulk phase is observed in the representative SEM image, (Fig.22
(d)). Based on XRD and SEM results, it can be inferred that the presence of Eu 3+ ions
prevents the formation of GaOOH nanorods or destroys the layered structure of GaOOH. In
order to understand thoroughly the role of Eu 3+ ions in the formation of GaOOH phase or on
the structural changes of GaOOH lattice, it is necessary to know structural features of
GaOOH and linkages between the basic building units constituting GaOOH lattice.
Accordingly, in GaOOH structure, six oxygen atoms forming an irregular octahedron
surround each Ga atom. Each octahedron shares edges with four neighbouring GaO 6
octahedra to form double chains along the c-axis. This structure consists of two nonequivalent
axial oxygen atoms namely O a and O b . One of the octahedral axes, i.e. GaO a is
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