Synthesis, characterization, and dielectric properties of Y2NiMnO6 ceramics prepared by a simple thermal decomposition route

Abstract

In attempt to search for an improved material preparation technique, Y2NiMnO6 dielectric material is prepared by a one-step thermal decomposition route where a solution of stoichiometric mixtures of metal acetates is directly heated. Structural characterization by X-ray diffraction and electron diffraction shows that the samples were successfully prepared at relatively low temperature comparing to a standard solid state synthesis. Results from several techniques including thermal analysis, electron microscopy, and X-ray absorption are used to investigate compound formation. It is revealed that metal acetates decompose at 300–350 °C resulting in mixture of several metal oxide intermediates which continue to react to form the desired product. Y2NiMnO6 nanoparticles are first obtained at 800 °C. Later, these nanoparticles agglomerate and grow at higher temperature and/or longer heating time to give larger particle size and more crystallinity. Although the starting reagent contains Mn in 2+ oxidation state, X-ray absorption near edge structure analysis indicates that the obtained Y2NiMnO6 contain Mn and Ni in 4+/3+ and 2+ oxidation states, respectively. Ceramic sample shows large dielectric constant of about 6,000–7,000 at 30–120 °C at 1 kHz. Dielectric constant and dielectric response of the sample are consistent with those reported in other works where different synthetic techniques were used. The activation energy of dielectric relaxation is similar to the energy required to transfer electrons between Ni2+ and Mn4+, thus the observed large dielectric constant is intrinsically related to electronic ferroelectricity due to charge ordering of Ni2+ and Mn4+.