Effect of sintering temperature on structural and piezoelectric properties of PNN-PZT ceramics

Sintering temperatures affect the structural and piezoelectric properties of PbNi_1/3Nb_2/3-PbZrO₃-PbTiO₃ system considerably; therefore the effect has been studied on mechano-chemically processed powder. This process involves activating mixed oxides of PbO, NiO, Nb₂O₅, ZrO₂ and TiO₂, and in the present study, calcination steps at an intermediate temperatures were skipped which are usually required in conventional solid state reaction methods and chemical routes. Single-phase formation was confirmed from XRD patterns which shows rhombohedral structure at higher sintering temperature. Investigations of the microstructure indicate almost linear increase in grain size from 0.98 m to 2.56 m when the sintering temperature was varied from 1050°C to 1150°C. A high value of planar coupling factor (k_p) = 67 per cent and piezoelectric charge coefficient (d 33 ~ 750 pm/V; (as determined from strain versus electric field curve at low field) were obtained for the ceramic specimens sintered at 1100°C. The maximum strain was observed ~ 0.21 per cent at 40 kV/cm applied field for the sample sintered at 1100°C for 4 h.