IP: 5.189.205.203 On: Tue, 25 Feb 2020 06:05:22 Copyright: American Scientific Publishers Delivered by Ingenta Copyright © 2020 American Scientific Publishers All rights reserved Printed in the United States of America Article Journal of Nanoscience and Nanotechnology Vol. 20, 4239–4243, 2020 www.aspbs.com/jnn Characteristics of Perovskites ReNiO 3 (Re = La and Nd) Prepared by Solid State Reaction in the Ambient of Oxygen Sangmo Kim 1 , Dang Hai Truyen 1 , Tae Heon Kim 2 , and Chung Wung Bark 1 ∗ 1 Department of Electrical Engineering, Gachon University, Seongnam 13120, Republic of Korea 2 Department of Physics University of Ulsan, Ulsan 44610, Republic of Korea In the proposed method, we could complete the synthesis with only 3 h of thermal treatment, which is relatively fast in comparison to the previously reported procedure, without an expensive gas- controlled chamber system. The compound comprises Re 2 O 3 and NiO 3 powders that were mixed thoroughly in a stoichiometric ratio in a ball mill for 24 h and then dried in an oven at a 100  C. The powder mixture was quickly calcined at various temperature for at least 3 h in an oxygen gas flow compared to conventional annealing method. After calcination at 1100  C, the detected XRD peaks matched well with peaks of the standard ABO 3 perovskite structure. Moreover, EDX and FT-IR spectral analysis results confirmed that the mixture had formed stoichiometry ReNiO 3 . All prepared samples comprised plate-like grains with a random orientation, and their average particle size was in the range of 1 to 3 m calculated from FE-SEM images. Keywords: ReNiO 3 , Nd, La, Oxygen, Solid-State-Reaction. 1. INTRODUCTION Perovskites ReNiO 3 (Re = Pr, Nd, La, Sm, Eu) have been increasingly studied owing to their interesting ferroelec- tric, magnetic, optical, and transport properties, including the occurrence of a metal-insulator (MI) transition at tem- peratures higher than 400 K [1–3]. Among them, NdNiO 3 and LaNiO 3 are well known for MI transition depending on temperature, and their phase diagram is controlled by the strong Ni–O–Ni bond angles. Their crystal structure consists of corner-sharing NiO 6 octahedra with Ni–O dis- tances being almost equal and the R ion in a high coordi- nation site [4–6]. This affects the magnetic structure that indicates the existence of an orbital ordering in the pres- ence of two different Ni sites [7]. The ReNiO 3 oxides are classified as charge-transfer-gap compounds with an oxy- gen p-like valence band and a d-like conduction band. The MI transition of ReNiO 3 has been reported to occur due to the broadening of the p-like band [7, 8]. However, most nickel oxide compounds are divalent, and there are a few compounds in which Ni adopts a higher oxidation state. Generally, rare-earth or alkaline-earth ∗ Author to whom correspondence should be addressed. ternary metal oxides have been used for semiconductor materials. Among these compounds, NdNiO 3 and LaNiO 3 are known as a narrow-band metallic conductor with a rhombohedral distorted perovskite phase [9, 10]. Nickel oxide compounds and their film forms can be synthe- sized by a variety of methods such as chemical vapor deposition, the sol–gel method, electrochemical synthesis, metal-organic chemical vapor deposition, molecular beam epitaxial growth, pulsed laser deposition, and solid-state reaction synthesis [11]. Although the solid-state reaction method is widely used for powder synthesis because it is a solvent-less, high-purity, low-cost, and environmentally friendly process, it is not widely used for nickel oxide compounds. Since nickel compounds are usually unstable at high temperatures due to their high Ni formal valences, it is known that stabilization of the Ni 3+ in the ReNiO 3 compound is hard to archive. Moreover, it is also difficult to fully oxidize the ReNiO 3 phase [12, 13]. For this reason, the reported preparation methods of ReNiO 3 (Re = Nd and La) require a high-pressure oxygen reaction cham- ber to maintain an oxygen pressure higher than 100 atm. Another known synthesis route is low-temperature cal- cination; in this case, the speed of reaction is limited J. Nanosci. Nanotechnol. 2020, Vol. 20, No. 7 1533-4880/2020/20/4239/005 doi:10.1166/jnn.2020.17557 4239