**4. Conclusion**

In the chapter the effect of Mn doped Nickel ferrite percentage in Lead Zirconate Titanate (PZT) at different sintering temperature on the piezoelectric and magnetoelectric behavior was tried to find out and also a new post sintering treatment (annealing and aging) is introduced to enhance the magnetoelectric property. It was found that with increasing percentage of NF the piezoelectric constants, dielectric constant decreases and dielectric loss increases. The starting powder of PZT-NF (3%, 5% and 10% NF) was found ferromagnetic where the coercive field varies from 97 to 124 Oe. Post sintering treatment like annealing and aging increases the saturation magnetization Ms from 48 to 57 memu for PZT-10NF. High values (~144 mV/cm Oe) of magnetoelectric coefficient were found in 10% NF, sintered at 1125°C. The preferential distribution of NF particles in large grains of PZT matrix was found in X-ray mapping. In order to even out the distribution of NF particles and increase the magnetic phases, annealing followed by aging was introduced, as annealing is a homogenization treatment. Due to annealing the piezoelectric property increases as well as magnetoelectric coefficient. The magnetoelectric coefficient was found 211 mV/cm Oe at 3 Hz with no D.C. magnetic field bias. This is higher than any values so far reported in PZT-10% NF and sintering temperature at 1125°C. A supersaturated structure of NF in PZT is formed by annealing at high temperature followed by faster cooling. Aging allows the NF particles to distribute evenly in the structure as a different phase. The XRD pattern also shows the introduction of spinel phases in PZT matrix. The SEM images also support the grain homogenization treatment. The introduction of this post sintering treatment (annealing and aging) enhanced the property and can be further improved with optimum parameters of the treatment.
