Low-temperature sintering of ZnO:Al ceramics by means of chemical vapor transport

Abstract

A new technological approach for sintering Al-doped ZnO ceramics using chemical vapor transport (CVT) based on HCl has been developed. Among the advantages of the proposed sintering approach are: the low sintering temperature of 1070 °C; the absence of deviation in the diameter of ceramics after sintering; and the presence of Zn excess in the resulting material. The influence of dopant powder, concentration of Al, powder compacting pressure, and stoichiometric deviation on the density and conductive properties of ceramics has been investigated. Due to the relatively weak interaction of Al2O3 with HCl and limited solubility of Al in ZnO, a doping level about 2 at.% is recommended. A further increase in the dopant concentration significantly reduces the density and conductivity of the resulting material. A theoretical and experimental comparative analysis of the features of CVT sintering of ZnO doped with Al, Ga, and In was also carried out. ZnO:Al:Cl CVT ceramics with the resistivity of 9.5 × 10–3 Ω cm can be used as stable magnetron targets for ZnO thin films deposition with improved conductive properties. The influence of dopant powder, Al concentration, deposition temperature, and the gaseous medium of sintering target on the electrical properties of films are investigated and discussed.