Ceramic processing and multiferroic properties of the perovskite YMnO$_3$-BiFeO$_3$ binary system

TL;DR

This study explores the processing and multiferroic properties of the YMnO$_3$-BiFeO$_3$ perovskite system, demonstrating advanced ceramic fabrication techniques and revealing phase coexistence, dielectric, and magnetic behaviors relevant for multifunctional device applications.

Contribution

It introduces the use of Spark Plasma Sintering for ceramic processing of YMnO$_3$-BiFeO$_3$, enabling phase stability and detailed electrical and magnetic characterization.

Findings

Successful densification at reduced temperatures prevented phase decomposition.

Enhanced dielectric permittivity observed in phase coexistence region.

Antiferromagnetic behavior confirmed in the rhombohedral phases.

Abstract

The perovskite (1-x)YMnO$_3$-xBiFeO$_3$ binary system is very promising because of its multiferroic end members. Nanocrystalline phases have been recently obtained by mechanosynthesis across the system, and the perovskite structural evolution has been described. Two continuous solid solutions with orthorhombic Pnma and rhombohedral R3c symmetries were found, which coexist within a broad compositional interval of 0.5 < x < 0.9. This might be a polar-nonpolar morphotropic phase boundary region, at which strong phase-change magnetoelectric responses can be expected. A major issue is phase decomposition at moderate temperatures that highly complicates ceramic processing. This is required for carrying out a sound electrical characterization and also for their use in devices. We present here the application of Spark Plasma Sintering to the ceramic processing of YMnO$_3$-BiFeO$_3$ phases. This advanced technique, when combined with nanocrystalline powders, allowed densifying phases at reduced processing temperatures and times, so that perovskite decomposition was avoided. Electrical measurements were accomplished, and the response was shown to be mostly dominated by conduction. Nonetheless, the intrinsic dielectric permittivity was obtained, and a distinctive enhancement in the phase coexistence region was revealed. Besides, Rayleigh-type behaviour characteristic of ferroelectrics was also demonstrated for all rhombohedral phases. Magnetic characterization was performed in this region, and antiferromagnetism was shown.