PZT-cobalt ferrite particulate composites: Densification and lead loss controlled by quite-fast sintering

During densification at 1100-1200 °C of particulate lead zirconate titanate (PZT)/cobalt ferrite (CF, 26-81  mol%) composites, side reactions do occur that are detrimental to the properties of the so-obtained material. Such reactions are promoted by initial PbO loss, the extent of which can be determined by means of XRD analysis of the densified samples taking into account the amount of ZrO2 and the variations of the perovskite's tetragonality. In this process, titania is produced which reacts with CF to form cobalt titanate. Microstructural characterization showed that CF grain size distribution can be mono- or bi-modal, and CF overgrowth was found to affect the coercivity of the material. In the case of the PZT:CF 74:26 composites, full densification and prevention of unwanted side reactions were achieved by designing a quite-fast sintering process. The high coercivity (789 Oe) displayed by these composites is related to the good dispersion of 250 nm euhedral CF grains in the PZT matrix and limited PZT grain growth (240 nm).