Synthesis of high magnetoelectric coefficient composites using annealing and aging route

In this paper, aging temperature and time dependence of ferroelectric, ferromagnetic, and magnetoelectric properties of lead zirconate titanate and nickel ferrite composite (1-x) Pb(Zr_0.52 Ti_0.48)O_3-x NiFe_1.9Mn_0.1 O₄ (PZT-NFM, x =0.03, 0.05, 0.1) are reported. The magnetoelectric composites of different compositions were fabricated by using a process based on the controlled precipitation route. The processing is a combination of conventional mixed oxide sintering and thermal treatment. The thermal treatment consists of annealing at a high temperature (800°C for 10 h), followed by aging in the range of 300-400°C for 3-15h. X-ray diffractometry patterns show variation in the amount of spinel phase with different aging temperature and time. Scanning electron microscopy investigation showed that the annealing and aging treatment increases the homogeneity of NFM in the PZT matrix. The magnitude of piezoelectric constant (d₃₃), piezoelectric voltage constant (g₃₃), and the dielectric constant exhibited significant variation in magnitude with aging time and temperature. Aging at 400°C for 5h exhibited a maximum magnitude of d₃₃ and g₃₃ and minimum magnitude of dielectric constant. The magnitude of the magnetoelectric (ME) voltage coefficient (dE/dH) for 0.9PZT-0.1NFM samples sintered at 1125 °C was found to be of the order of 78m V/cm Oe. This magnitude increased to 140 mV/cm Oe after annealing and aging at 300°C for 5 h. This significant enhancement in the magnetoelectric coefficient is probably due to the homogenization and precipitation of the spinel (NFM) phase in the perovskite matrix.