Transparent conducting oxides (TCOs), such as Sn-doped In2O3 (indium doped tin oxide, ITO), Al-doped ZnO (AZO), Sb-doped SnO2 (ATO), and F-doped SnO (FTO), have the unique feature of combining optical transparency in the visible region (colorless state) with metal type electrical conductivity. Therefore, they are widely applied as transparent electrodes for liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), solar cells, etc. (Fig. 1) [1-3]. A TCO is a semiconductor with a wide bandenergy gap (≥ 3 eV), which confers the optical transparency. It has also quasi free electrons in its wide conduction band of s-character; the free electrons confer the metal type conductivity. These arise either from defects in the material or from extrinsic dopants which introduce electron donor centers that underlie the conduction band edge. During the last thirty to forty years, the dominant doped TCOs have been based on tin oxide (SnO2), indium oxide (In2O3), and zinc oxide (ZnO) [1-4]. Fig. 2 shows the improvement of the electrical conductivity achieved for these three dominant families of TCO materials over the last 35 years. In spite of all these intensive investigations, there is still a need to have TCOs with better optimized opto-electronic properties. That is particularly needed (in our case) for the following applications: heat reflectors, transparent micro-furnaces and flexible electrochromic devices, that will be discussed later on in this thesis. That led us to carry out studies on the following TCOs, in both ceramic and thin film forms: (i) ATO and AZTO (tin dioxide co-doped with antimony and zinc) (ii) ITZO (indium trioxide co-doped with tin and zinc).