Stoichiometry and Grain Boundaries Control by Spark Plasma Sintering in Ba_0.6Sr_0.4TiO₃:Mn/MgO Composites

Abstract

This study highlights the possibility to control materials' chemistry simultaneously at the atomic and micrometric scales and to design functional oxide-based multimaterials, thanks to the specificity of Spark Plasma Sintering (SPS). We have used a dual synthesis route, namely chemical and composite, combined with SPS to adjust the oxidation state of intrinsic and dopant ions, the grain boundaries state, and to control interdiffusion in composites made of Mn-doped Ba 0.6 Sr 0.4 TiO 3 (BST) and MgO. At the atomic level, the Mn substituent valence state can be fixed according to the sintering process: Electron Paramagnetic Resonance evidenced Mn 2þ Ti , Mn 4þ Ti , and Mn 2þ Ti -V O charged defects. We established a link between the nature of the charged defects and the high-frequency dielectric losses. At the microscopic level, control of the grain size, the grain boundaries, and the interdiffusion between the components is achievable using SPS. The composite effect acts at low frequency by efficiently decreasing the extrinsic losses arising from the grain boundaries contribution and by increasing the thermal stability of the permittivity. Such an approach based on SPS, chemical and composite routes, has allowed designing BST-based composites operating in a wide frequency range (kHz-GHz) with low dielectric losses and high electric field tunability.C. Randall-contributing editor Manuscript No. 30475.

Innovative architectures in ferroelectric multi-materials: Chemistry, interfaces and strain

“…A small addition of magnesium oxide (4 wt.%) as a dielectric phase acts efficiently as a dielectric barrier for grain boundaries extrinsic (low frequency) losses while a 1 mol.% Mn substitution in the ferroelectric matrix effectively lowers the intrinsic (high frequency) losses thanks to electron-trapping by the acceptor Mn defects. 51 The dual scheme combines these effects in a low dielectric losses (< 1.5%) material over a wide frequency range 10 kHz-1 GHz, keeping high tunability (Fig. 6).…”

3D mapping of anisotropic ferroelectric/dielectric composites

“…The optimal value in order to decrease the low frequency dielectric losses while keeping sufficiently high permittivity tunability is around 4 wt% MgO. 8 …”

“…For this purpose, we processed composites made of a Ba 0.6 Sr 0.4 TiO 3 (BST) ferroelectric matrix in which MgO inclusions were spread. [6][7][8] While the former provides unique dielectric flexibility, the latter drives dielectric losses towards the levels required by the electronic industry. 9,10 In the present study, we go beyond this accumulation of properties and show a real composite effect.…”

Effect of Oxygen Annealing on the Electrical Properties of PBLZST Anti-ferroelectric Ceramics

“…This result is consistent with the previous work of Catherine Elissalde. 23 The lengthy sintering process produces a fairly high level of oxygen absence and internal stress. During the conventional sintering, the compensation effect reaches a balance between the oxygen absence and A site absence.…”