NANO-CRYSTALLINE YTTRIA SAMARIA CODOPED ZIRCONIA: COMPARISON OF ELECTRICAL CONDUCTIVITY OF MICROWAVE AND CONVENTIONALLY SINTERED SAMPLES

摘要

A systematic study on powder preparation, compaction and sintering in conventional heating and microwave (MW) field has been carried out for yttria samaria codoped tetragonal zirconia polycrystal and the electrical conductivity of the sintered samples has been compared. The powder compositions, selected as (Y2O3)_x - (Sm2O3)_(3-x) - (ZrO2)_(97) (where, x takes the values of 0, 1,2 and 3) were prepared by co-precipitation method. Based on simultaneous thermo-gravimetry and differential thermal analysis (TG-DTA) study the calcination temperature was selected as 800°C. The diffractograms of the calcined powders confirmed the presence of tetragonal phase. Several techniques were used to determine particle size of the wet ground powder. Shrinkage behaviour of the sample studied by dilatometric technique indicated an increase in sintering onset temperature with samaria content. Isothermal sintering studies were carried out under conventional heating and microwave field. In both the cases high density (95-99% of theoretical density) was obtained at 1200°C temperature for all the compositions. Sintering in MW furnace resulted in a marginally denser sample compared to its conventionally sintered counterpart. Electrical conductivity of the samples measured by two-probe AC impedance spectroscopy in the temperature range of 350°-750°C revealed that activation energy for ionic conduction decreases when samples are sintered in microwave field.