Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Gas sensing and electrochemical properties of rare earthferrite, LnFeO 3 (Ln = Nd, Sm) Zakie Anajaf a,b , Mahmoud Naseri b,∗ , Giovanni Neri a a Department of Engineering, University of Messina, Messina, Italy b Department of Physics, Faculty of Science, Malayer University, Malayer, Iran ARTICLE INFO Keywords: Conductometric sensor Electrochemical sensor Acetone Dopamine Rare earth Ferrite ABSTRACT In this paper, nanostructured perovskite-type LnFeO 3 (Ln = Nd, Sm) oxides were synthesized by thermal treatment method (TTM). Characterization analysis conducted by X-ray difraction (XRD), scanning electron microscopy (SEM) and micro-Raman spectroscopy, have confrmed the perovskite structure of the synthesized nanomaterials. To study the efects of Nd and Sm lanthanides substitution at the A-site on the chemical sensing performance, conductometric and electrochemical sensors based on the synthesized LnFeO 3 samples were fab- ricated. LnFeO 3 -based conductometric and electrochemical sensors were tested for acetone and dopamine sen- sing, respectively. The data revealed that Nd and Sm in the A-position lead to a signifcant infuence in the gas sensing and electrochemical properties of perovskite LnFeO 3 samples. In particular, it has been demonstrated the good gas sensing characteristics of SmFeO 3 for acetone gas (Response = R/R 0 = 8.3–20 ppm acetone at 200 °C), whereas NdFeO 3 displayed better performance as electrode for the electrochemical detection of dopamine reaching a low detection limit (LOD) of 270 nM at S/N = 3. The electrical and electrochemical characteristics of the perovskite LnFeO 3 samples were discussed in detail with respect to their chemical composition and micro- structure. 1. Introduction Perovskite structure materials possessing an ABO 3 formula have been widely used in diferent applications thanks to their unique magnetic, thermoelectric, catalytic properties coupled with very good thermal and chemical stability as well as electronic conductivity [1]. These materials usually contain a rare earth cation in position A and a transition metal in position B. Recently, perovskites have been also well considered for their promising properties in the chemical sensors, in particular those based on electrical and electrochemical transduction efects [2,3]. Advances in these chemical sensors are for practical im- portance in many applicative felds, such as in the environmental control, agriculture, industrial processes and in biomedicine. For these applications, other than the sensitivity and selectivity, the long term life and stability of the sensor are also essential requisites, which could beneft of the well known high thermal and chemical stability of per- ovskites [4–6]. Semiconducting metal oxides-based gas sensors have been largely investigated in the monitoring of a variety of gases [7]. The development of these sensors with promising performances by using novel semiconducting perovskite materials has attracted recently many interest [8–14]. The most interesting point for these materials in gas sensing derive from their chemical composition and structure which can ofers various combinations leading to diferent sensing char- acteristics and gas detection [15–18]. Acetone is a gas which has been established, at very low concentration in the human breath, as a bio- markers for diabetes [19–22]. Perovskites have been also proposed for electrochemical sensors [23]. Electrochemical sensors based on metal oxides like CuO, NiO, SnO 2 [24–26], or metallic nanoparticles, e.g. Pt, Pd, Au [27–29], generally display good performance, because of their large surface-to-volume ratio and small particle size analogous to the extension of surface charge region. These properties, enhancing the mass transport and catalysis, ofer many advantages compared to con- ventional enzyme-based electrochemical sensors. Even if the B metal in the perovskite play the central role, providing the requested electron charge transfer, e. g. through the modifcation of its oxidation state, A- site metal in perovskites also provides the possibility to modify the electrocatalytic performance towards electroactive substances. Elec- troactive biomolecules such as dopamine (DA) are essential messenger for the neurotransmission of the nerve impulse in the central nervous system. The depletion of DA can lead to Parkinson's disease; therefore, it is very important to develop sensors which can be detect DA [30–32]. In this work we have focused our attention on rare earth ferrites, https://doi.org/10.1016/j.ceramint.2020.07.139 Received 21 April 2020; Received in revised form 30 June 2020; Accepted 13 July 2020 ∗ Corresponding author. Tel.: +988133339841/+989126868423; fax: +988133339843. E-mail addresses: m.naseri@malayeru.ac.ir, mahmoud.naseri55@gmail.com (M. Naseri). Ceramics International 46 (2020) 26682–26688 Available online 13 August 2020 0272-8842/ © 2020 Elsevier Ltd and Techna Group S.r.l. All rights reserved. T