Structural, electrical and magnetic properties of Nd \u2013 A \u2013 CoO3 (A\u2009=\u2009Sr, Ca) Perovskite Powders by Mechanical Alloying

Celal Kursun,Fatih Samil Uludag,Musa Gogebakan,Mehmet S Bozgeyik,Esra Uludag

doi:10.1038/s41598-018-31458-7

Abstract

In this work, NdCoO3 (NCO), Nd0.8Sr0.2CoO3 (NSCO) and Nd0.9Ca0.1CoO3 (NCCO) perovskite cobaltites were synthesised by mechanical alloying method. Structural evolutions, magnetic and electrical properties of these perovskite were systematically examined through X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray detection (SEM-EDX), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), vibration sample magnetometer (VSM) and impedance analyser (IA). The XRD and SEM results revealed that the microstructure of the perovskite materials changed during mechanical alloying. The average crystallite size of the perovskite materials was calculated by Debye Scherrer equation and was confirmed by TEM, and it was determined ~19 nm. From the VSM results, the all perovskites had soft ferromagnetic properties. IA measurements showed that relatively dielectric constants of the perovskites decreased with increasing frequency. Therefore, for the first time, nanostructured NCO, NSCO and NCCO perovskites exhibiting good properties were produced in only two steps which are milling and heating.

Highlights

Rare earth perovskite cobaltite with the general composition of ReCoO3 and the doped mixed oxides with the general composition of Re1−xAxCoO3 have been extensively studied for their potential applications, where Re is for trivalent rare earth elements such as La, Pr, Nd, Eu, Gd, Ny and A is for divalent alkaline earth elements such as Ba, Sr, Ca, P or Mg
The microstructural evolutions of the NCO, NSCO and NCCO powders were performed by SEM to reveal the morphological changes and the decrease in the particle size during mechanical milling
The NdCoO3 (NCO), Nd0.8Sr0.2CoO3 (NSCO) and Nd0.9Ca0.1CoO3 (NCCO) perovskites were manufactured from nitrate salts ball milled for various periods of times from 4 h to 48 h and they were subjected to heat treatment at 1000 °C for 2 h after 48 h milling

Summary

Introduction

Rare earth perovskite cobaltite with the general composition of ReCoO3 and the doped mixed oxides with the general composition of Re1−xAxCoO3 have been extensively studied for their potential applications, where Re is for trivalent rare earth elements such as La, Pr, Nd, Eu, Gd, Ny and A is for divalent alkaline earth elements such as Ba, Sr, Ca, P or Mg. The cobalt oxides have properties of hopping of eg electron double-exchange interactions (DE) between Co+3 and Co+4 ions which depend on the Co-O-Co bond angle and Co-O bond length like in manganates[18,19] Both trivalent and tetravalent cobaltites exhibit two magnetic transitions with increasing temperature. Because of this reason both the spin state and the ionic radius of Co+3 ion increase (Ionic radius for Co+3 rLS = 0.545 Å, rIS = 0.560 Å and rHS = 0.610 Å) This change can be explained by the Hund energy in the CoO6 octahedron, Jahn Teller effect, double-exchange mechanism and collerated polarons[26,27,28].

Methods

Results

Conclusion