Specific core-shell approaches and related properties in nanostructured ferroelectric ceramics

Abstract

Interfaces are a major issue when designing ferroelectric nanostructured materials with tailored properties. In a context of integration and multifunctionality in the field of electronics, several strategies have been developed to control the microstructure and defect chemistry of interfaces that strongly impact the macroscopic properties. The suitability of the core-shell approaches that allow a subtle tuning of interface phenomena at different scales has been widely demonstrated. We focus here on the flexibility of the core-shell approach devoted to the processing of nanostructured ferroelectric composites. Our strategy relies on the use of advanced synthesis processes to design ferroelectric grains coated with shells of different nature, morphology and crystallinity. Typical examples will be reviewed with a specific attention on their impact on both microstructure and dielectric properties. Our approach, based also on the use of fast sintering technique, provides a guidance to design 3D bulk nanostructured ferroelectrics while controlling and/or exploiting size, interface and defects chemistry. The contribution of specific spectroscopies to probe interfacial chemistry and defects is underlined. The high density of interfaces in core-shell materials is obviously an advantage to target additional functionality such as magneto-electric coupling. This is illustrated in 3D composites and one dimensional nanostructures that coaxially combine electric and magnetic materials. The core-shell approach described here could be transferred to a much broader range of materials covering many functionalities provided a deeper understanding of the interfaces at the atomic scale is achieved and a further development of low temperature processing is reached.

Magnetoelectric nanoparticles shape modulates their electrical output

“…Frontiers in Bioengineering and Biotechnology frontiersin.org 2016a; Elissalde et al, 2018). In fact, when the magnetostrictive and the piezoelectric phases are tightly bonded, the strain generated in the core homogenously transfers to the shell, thus more efficiently triggering the electrical field generation.…”

The Role of Sacrificial and/or Protective Layers to Improve the Sintering of Electroactive Ceramics: Application to Piezoelectric PZT-Printed Thick Films for MEMS

“…They can be located either directly in contact with the powder or between the rams and punches [58]. Alumina powders were also used to prevent ferroelectric ceramics from chemical reduction during SPS [16] and to prevent the pistons of the deforming copper spiral extremities in the co-sintering of transformers for power electronics [59]. Alumina powder placed on both sides of ZnO samples were also used to insulate ZnO from the current.…”

“…In the second part of this paper, original approaches targeting bulk ceramic and thick-film ceramic MEMS produced using advanced sintering techniques associated with protective layers are introduced. While sacrificial materials have already been shown to act as a pore forming agent or as a thermal or diffusion barrier for bulk ceramics [15,16], carbonate based protective materials have recently appeared to efficiently prevent PZT from chemical reduction during spark plasma sintering (SPS) [17]. Chemistry, microstructure, and stress/strain effects are again issues strongly linked to sintering and whose control has an impact on the performance of the electroactive multilayer.…”

One step densification of printed multilayers by SPS: Towards new piezoelectric energy harvester MEMS

“…Alumina powders were also used to prevent ferroelectric ceramics from chemical reduction during SPS sintering (Elissalde et al, 2018) and to prevent the pistons of deforming copper spiral extremities in SPS co-sintering of transformers for power electronics (Mercier et al 2016).…”