Inter-relationship between structure and dielectric properties of crystalline anodic zirconia

Crystalline anodic oxide films have been formed on sputter-deposited zirconium and Zr-Ti alloys in 0.1 mol dm−3 ammonium pentaborate electrolyte, with their structure, composition, dielectric properties and growth behaviour examined using X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy, glow discharge optical emission spectroscopy and electrochemical impedance spectroscopy. The films formed on zirconium consist of a high-temperature stable ZrO2 phase (cubic or tetragonal) as well as monoclinic ZrO2, with the latter predominant with increasing formation voltage. The incorporation of titanium species into the films stabilizes the high-temperature phase up to high voltages. Associated with the change in the crystalline structure with the incorporation of titanium species, the permittivities of the oxides increase, in agreement with the higher permittivity of bulk cubic and tetragonal ZrO2 containing stabilizing cations compared with that of bulk monoclinic ZrO2. The transport number of cations during crystalline oxide growth is about 0.05, irrespective of titanium incorporation.