Nb-Doped PZT

The PZT and Nb-doped PZT (PZTN) ceramics were synthesized from triol sol-gel-derived powders [95]. The reagents used were zirconium(IV) propoxide and acetylacetone prepared in a dry nitrogen atmosphere. The mixture was refluxed in an oil bath at 90 °C for 2 h. The solution was then cooled down to room temperature before adding titanium(IV) isopropoxide, lead(II) acetate trihydrate, and l,l,l-tris(hydroxymethyl)ethane. The obtained gels were dried at 120 °C and thermally treated at different temperatures up to 600 °C. 

The pellets pressed from the obtained powders were sintered at temperatures in the range of 1050-1200 °C for 2h. Coexistence of tetragonal and rhombohedral phases was clearly observed in PZT ceramics sintered at 1150 °C, whereas PZTN ceramics showed coexistence of these phases at 1100 °C. Densities of undoped PZT ceramics were rather low but could be improved with the addition of Nb. Grain growth inhibition was also observed in all PZTN samples. The dielectric constant was found to depend mainly on density of the ceramics. An addition of Nb dopant to PZT improved dielectric constant values regardless of sintering temperature. 

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Figure 18.17 Comparison of ferroelectric hysteresis loops. Soft (1.0atom% Nb-doped) PZT (58/42) ceramics and hard (1.0atom% Fe-doped) PZT (58/42) ceramics relaxed by ac-field cycling at 125 °C. The measurements are carried out under the same conditions.

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