Gallium-doped zinc oxide powders have been prepared with electrical co
nductivities at 25 degrees C as high as 300 Omega(-1) cm(-1), more tha
n 1000 higher than previously reported. All materials prepared can be
represented as Zn1-xGaxO, Zn1-yGayO1+(y/2), or a combination of these
two. For Zn1-xGaxO, the room-temperature conductivity increases monoto
nically with increasing x up to 2.7%, which is the limit of Ga solubil
ity for this formulation at our synthesis temperatures of 1000 to 1200
degrees C. Conductivities measured from 4.2 to 500 K showed only a ve
ry small temperature dependence. An ESR peak (g = 1.96), attributed to
the conduction electrons, broadens with increased doping level. The h
exagonal unit-cell edges increase with increasing x over the entire ra
nge of x. For the low conductivity Zn1-yGayO1+(y/2) series, the level
of Ga substitution can reach at least 4.0%.