CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

CHAPTER 3: Binary oxides
3.1. Introduction: Oxides like Ga 2 O 3 and Sb 2 O 3 belong to class of materials known as
transparent semiconducting oxides and find extensive applications in electro-luminescent
devices, sensor materials for absorption of molecules like CO and CO 2 , catalysts, fire
retardants, anode material for the Li-ion batteries, etc. [48-51, 128-137]. Ga 2 O 3 exists in a
variety phases, namely α, β, γ and ε modifications [138, 139], whereas Sb 2 O 3 exists in two
crystalline forms, cubic (senarmonite form) and orthorhombic (valentinite form). Depending
on the nature of crystallographic modifications, they have different properties. For example,
cubic Sb 2 O 3 is used as an additive to improve the flame retardency of polymer resins whereas
valentinite form of Sb 2 O 3 is an essential component in Sb 2 O 3 -B 2 O 3 glasses showing enhanced
non-linear optical properties [140]. Similarly β-Ga 2 O 3 is a preferred material in optoelectronics
for field emission applications. Different phases of gallium oxides are generally
prepared by decomposition of a suitable precursor, like GaOOH whereas Sb 2 O 3 is generally
prepared either by the oxidation of antimony metal or by the hydrolysis of SbCl 3 . Several
reports are available [141-149] on the synthesis of GaOOH in different shapes and sizes.
These include methods like, hydrothermal treatment, sono-chemical reactions and
precipitation in aqueous medium by addition of urea. It is also observed that the shape is
retained when GaOOH is thermally decomposed to Ga 2 O 3 [56, 150]. A number of reports are
also available on the preparation of Sb 2 O 3 in variety of forms such as nanoparticles [151-
158], hollow nanospheres [159], nanowires, nanobelts and nanorods [64, 65, 160-163].
Doping GaOOH/ Ga 2 O 3 and Sb 2 O 3 nanomaterials with lanthanide ions (Ln 3+ ) is an attractive
option to prepare efficient luminescent materials. In the following section a brief description
on the optical and luminescence properties of both lanthanides, doped and undoped GaOOH
and Sb 2 O 3 have been discussed.
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