Multilayer Ceramic Magnetoelectric Composites with Tailored Interfaces for Enhanced Response

Abstract

Composite materials consisting of two dissimilar ferroic phases are an excellent alternative to single-phase multiferroics for a wide range of magnetoelectric technologies. In composites with strain-mediated magnetoelectric coupling the response is strongly dependent on the characteristics of the interface between the two mechanically coupled phases. Among the different material approaches considered, cofired ceramic composites offer improved reliability in applications and are more adequate for free-forming and miniaturization. However, their magnetoelectric response often suffers from poor reproducibility, which has been reiteratively associated with the quality of the interfaces with little experimental support. Here, we report an in-depth study of the local material properties across the interfaces of 0.36BiScO-0.64PbTiO/NiFeO multilayer ceramic composites, processed by spark plasma sintering of nanocrystalline powders. Tailored microstructures and low residual stress levels were obtained by adjusting the sintering mismatch between the two ferroic phases, which also resulted in fully functional interfaces and enhanced magnetoelectric responses.

Investigations of ferroelectric polycrystalline bulks and thick films using piezoresponse force microscopy

“…In the case of lead-based ceramics, PFM analyses of domain structures were performed in PbTiO 3based [68][69][70] [33] and Pb(Fe 1/2 Nb 1/2 )O 3 -based [80] ceramic samples. The domain structures in lead-based ceramic samples vary significantly, from typical macro-sized domains [33,49,56,68,69] in ferroelectrics to polar nano-domains (PNDs) in relaxors [33,53,71,72,74], which are often called labyrinth-type [71,72] or finger-print nanoscale domains [53] or nanoscale quasi-regular maze domains [53,74].…”

Insights into the Performance of Magnetoelectric Ceramic Layered Composites

“…Maximum α 31 E values of 21, 24, and 8 mV·cm −1 ·Oe −1 were obtained in the ceramic composites spark plasma sintered at these temperatures [18]. Note that figures do not coincide with those reported in [18], for the piezoelectric thickness was used in that case to normalize the magnetoelectric response.…”

“…Actually piezoresponse force microscopy (PFM) studies of this specific interface have shown that grains attached to the NIFe 2 O 4 layers are piezoelectrically active as it is illustrated in the inset. Moreover, an in-depth recent study has demonstrated fully-functional interfaces [31]. Therefore, this mechanism is not responsible for the reduction of the response in the specific case under study.…”

“…However, simulations show that such structures do not have the same response for a given geometry, as it is illustrated in Figure 3, where 8 mm long, 2 mm thick structures with a piezoelectric fraction of 0.5 are compared. It is found that the three-layer structure shows a significantly higher maximum α 31 E than the two-layer one:…”

“…The same year, exact analytical expressions were reported for the effective magnetoelectric coefficient α zz of laminate composites with axial symmetry distinguishing the cases of mechanically free and clamped boundaries [11]. Analytical expressions for the corresponding effective coefficient α ρz were later obtained, and compared with experimental values of α 31 for a number of ceramic systems [12]. A phenomenological interface coupling parameter was introduced in the formalism to account for the possible partial disruption of strain transmission across the interface.…”