Processing bulk and nanostructured ferroic materials at low temperatures

Thanks to the tunability of their properties, ferroic oxides are ideally suitable for passive components for electronics such as capacitors, memory devices, filters, piezoelectric transducers. The current expectations are... [ view full abstract ]

Thanks to the tunability of their properties, ferroic oxides are ideally suitable for passive components for electronics such as capacitors, memory devices, filters, piezoelectric transducers. The current expectations are driven by the needs to deliver ever-greater levels of functionality within smaller devices. In this context combining or coupling electronic and magnetic properties in a multifunctional material is very appealing. Simultaneously, transition towards more sustainable technologies requires energetically efficient and environment-friendly processes, possibly by enabling low temperature processing. These trends converge towards the low-temperature processing of multiferroic materials and composites,a current challenge that opens new pathways for better control of interfaces and microstructure, and provides the opportunity to explore new materials.

This approach will first be illustrated through the design of innovative magnetoelectric heterostructures. New routes combining electrodeposition, sol-gel and radio frequency sputtering deposition have allowed to control interfaces and material chemistry in BaTiO₃-CoFe₂O₄ nanopilar arrays based nanostructures and Pb(ZrTi)O₃ - CoFe₂O₄  core-shell nanocables¹. The oxidation of the metal CoFe₂ into  CoFe₂O₄ phase is the critical step. Lowering the processing temperatures or optimizing the thermal cycles help to solve critical issues related to interdiffusion at interfaces.

In a second part, we will emphasize the potentiality of Cool-SPS to develop new magnetoelectric ceramics². Cool-SPS provides a unique opportunity to explore thermodynamically fragile materials (low temperature decomposition, phase transition,...) selected for their potential (multi)ferroic or magnetoelectric properties. An illustration will be given through the case of MnSO₄, for which a complex sintering mechanism has been deciphered, and evidences for a magnetoelectric coupling collected.

We will conclude by the timely convergence between low temperature processes, the increasing complexity of multifunctional materials and the opportunity to develop the class of thermodynamically fragile, but sustainable, materials.

¹S. Basov et al. Nanotechnology, 28, 475707, 2017.

²T. Hérisson de Beauvoir et al. J.Mater.Chem. C in press, 2018.  .