HIGH-TEMPERATURE IONIC-CONDUCTION IN MULTICOMPONENT SOLID OXIDE SOLUTIONS BASED ON ZIRCONIA

High-temperature ionic conductivity of zirconia-calcia (ZrO2-CaO), zir conia-yttria (ZrO2-Y3O3), and zirconia-rare-earth-oxide (ZrO2-RE2O3) s olid solutions was measured at temperatures of 1000 degrees-1600 degre es C. The emf polarization method and a thermodynamic emf method using a new reference system (aluminum melt coexisting with solid alumina) were applied to obtain the parameters p(e') characterizing ionic condu ctivity. In the present study, the parameter p(e') has been investigat ed as a function of temperature, of dopant radius, of dopant concentra tion, and of conditions of preparation. In the range of the investigat ed dopant concentrations, parameter p(e') was shown to decrease as the dopant radius decreased. For the system ZrO2-Y2O3, a minimum of the p arameter p(e') was observed at 25 mol% Y2O3. In addition to this, it i s important to take into account the sintering parameters, the purity, and the grain size of the used samples to compare the results with pr evious data. A comparison of the parameter p(e') of CaO- and Y2O3-dope d ZrO2 and of RE2O3-doped ZrO2 indicates that the relevant values of Z rO2-RE2O3 solid solutions are one to two orders lower Additional studi es on new multicomponent solid solutions based on ZrO2 also revealed p romising high-oxygen-ion-conductive solid electrolyte materials in vie w of low values of parameter p(e'). Wide ranges of cubic solid solutio ns were identified by X-ray diffractometry. It was demonstrated that t he two experimental techniques can successfully be used to determine m ixed ionic and electronic conduction in commonly used solid oxide elec trolyte materials, e.g., for practical oxygen sensors in metal melts.