Phase concentration and microstructure effects on the properties of hot-pressed PZN-PT/CFO magnetoelectric composites

Reference Presenter Authors
(Institution)
Abstract
08-138 Ducinei Garcia Garcia, D.(Universidade Federal de São Carlos); Rosa, W.S.(Federal University of São Carlos); Milton, F.P.(Universidade Federal de São Carlos); Perdomo, C.F.(Universidade Federal de São Carlos); Gualdi, A.J.(Universidade Federal de São Carlos); Kiminami, R.H.(Universidade Federal de São Carlos); Eiras, J.A.(Universidade Federal de São Carlos); Oliveira, A.J.(Universidade Federal de São Carlos); Zabotto, F.L.(Universidade Federal de São Carlos);

Perovskite ferroelectrics based on compositions within the morphotropic phase boundary (MPB) region can feature maximized piezoelectric coefficients, which make them an excellent choice for pairing with a magnetic phase in magnetoelectric composites. The MPB compound 0.90[Pb(Zn1/3Nb2/3O3)]-0.10(PbTiO3) or simply 0.9PZN-0.1PT, which presents giant piezoelectric coefficient in the single crystal form, however, does not stabilize as a ferroelectric phase when conventionally prepared as powder. Nevertheless, recent works have reported that 0.9PZN-0.1PT with 100% of ferroelectric perovskite phase can be achieved in biphasic magnetoelectric particulate composites prepared by a novel in situ Pechini method. In this study, ceramic bodies were first-time sintered by the application of uniaxial hot pressing on 0.9PZN-0.1PT/CoFe2O4 Pechini-synthetized nanopowders, with the intent of enhancing the magnetoelectric response through adequate grain growth and densification. Phase identification analysis using X-ray diffraction technique revealed that the PZN-PT phase was preserved as a perovskite after hot pressing. The ferrite cobalt concentration was varied relatively to the ferroelectric phase to take into consideration its effects on ferroelectric, magnetic and coupled properties. Scanning electronic microscopy revealed that the ferroelectric/magnetic phase ratio affects the final microstructure of the composite, since higher ferrite concentrations yielded smaller average grain sizes in both phases. The results showed that the magnetic and/or electric properties were affected differently, not only because of the grain size distribution but also due to the percolation degree developed for each concentration. The discussions are based on the relationship between the features of these composite microstructures and the overall magnetic-ferroelectric properties.