Colossal dielectric response, multiferroic properties, and gas sensing characteristics of the rare earth orthoferrite LaFeO₃ ceramics

A great impact of the multifunctional or multiferroic materials on device applications has gained tremendous attention from scientific research groups in the field of materials science. The multiferroic materials bear superior properties of alternating the ferroic orders in a pre-designed way to match the device specifications. Materials in which there is a coupling between the primary ferroic orders (ferroelectric, ferromagnetic, ferroelastic) are termed multiferroics. This paper shows the investigation of a room temperature multiferroic material bearing a chemical composition LaFeO₃ (LFO) also known as rare-earth orthoferrites. The particles of LFO are synthesized employing mixed oxide processing with heat treatment. The Rietveld analysis of the material shows that the LFO crystallizes having an orthorhombic symmetry and Pbnm space group. The complex impedance spectra indicate the distribution of relaxation time and non-Debye-type behavior. The dielectric parameters measured at various frequencies and temperatures suggest the formation of a colossal dielectric constant and low loss. The elemental analyses of the material show that there is no impurity present in the material. The pellet of the LFO arranged in a metal-insulator-metal arrangement is tested for gas sensing application. The LFO material has an excellent selectivity towards NO₂ gas at relatively low operating temperatures ranging from 50 °C to 300 °C along with a sub-ppm limit of detection. A set of cyclic testing confirms that LFO can carry out stable and lengthy gas sensing operations while demonstrating outstanding adsorption and desorption characteristics. Such superior gas sensing properties and dielectric characteristics can pave the way toward the ultra-high sensitive gas sensors based on lead-free orthoferrites perovskites.