Influence of the Sintering Method on the Properties of a Multiferroic Ceramic Composite Based on PZT-Type Ferroelectric Material and Ni-Zn Ferrite

This paper presents the research results of multiferroic ceramic composites obtained with three sintering methods, i.e., free sintering FS (pressureless), hot pressing HP, and spark plasma sintering SPS. The multiferroic composite was obtained by combining a ferroelectric material of the PZT-type (90%) and zinc-nickel ferrite (10%). Research has shown that the combination of a magnetic material and ferroelectric materials maintains the multiferroic good ferroelectric and magnetic properties of the composites for all sintering methods. A sample sintered with the HP hot pressing method exhibits the best parameters. In the HP method, the composite sample has high permittivity, equal to 910 (at room temperature) and 7850 (at the phase transition temperature), residual polarization 2.80 µC/cm(2), a coercive field of 0.95 kV/mm, and the magnetization of 5.3 and 4.95 Am(2)/kg at −268 °C and RT, respectively. Optimal technological process conditions are ensured by the HP method, improving the sinterability of the ceramic sinter which obtains high density and proper material compaction. In the case of the SPS method, the sintering conditions do not allow for homogeneous growth of the ferroelectric and magnetic component grains, increasing the formation of internal pores. On the other hand, in the FS method, high temperatures favor excessive grain growth and an increase in the heterogeneity of their size. In obtaining optimal performance parameters of multiferroic composites and maintaining their stability, hot pressing is the most effective of the presented sintering methods.