High Conductivity in Gallium-Doped Zinc Oxide Powders

Gallium-doped zinc oxide powders have been prepared with electrical conductivities at 25 °C as high as 300 Ω - 1 cm - 1, more than 1000 higher than previously reported. All materials prepared can be represented as Zn 1 - x Ga x O, Zn 1 - y Ga y O 1+( y /2), or a combination of these two. For Zn 1 - x Ga x O, the room-temperature conductivity increases monotonically with increasing x up to 2.7%, which is the limit of Ga solubility for this formulation at our synthesis temperatures of 1000 to 1200 °C. Conductivities measured from 4.2 to 500 K showed only a very small temperature dependence. An ESR peak ( g = 1.96), attributed to the conduction electrons, broadens with increased doping level. The hexagonal unit-cell edges increase with increasing x over the entire range of x . For the low conductivity Zn 1 - y Ga y O 1+( y /2) series, the level of Ga substitution can reach at least 4.0%.