Low-Temperature Synthesis and Thermodynamic and Electrical Properties of Barium Titanate Nanorods

Florentina Maxim,Florina Teodorescu,Daniela Berger,Speranta Tanasescu,Cecilia Lete,Cristian Hornoiu

doi:10.1155/2015/827641

Florentina Maxim, Florina Teodorescu + Show 4 more

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https://doi.org/10.1155/2015/827641

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Abstract

Studies regarding the morphology dependence of the perovskite-type oxides functional materials properties are of recent interest. With this aim, nanorods (NRs) and nanocubes (NCs) of barium titanate (BaTiO3) have been successfully synthesized via a hydrothermal route at temperature as low as 408 K, employing barium acetate, titanium isopropoxide, and sodium hydroxide as reagents without any surfactant or template. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray powder diffraction (XRD), used for the morphology and structure analyses, showed that the NRs were formed by an oriented attachment of the NCs building-blocks with 20 nm average crystallites size. The thermodynamic properties represented by the relative partial molar free energies, enthalpies, and entropies of the oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressure of oxygen, indicated that NRs powders have lower oxygen vacancies concentration than the NCs. This NRs characteristic, together with higher tetragonallity of the structure, leads to the enhancement of the dielectric properties of BaTiO3ceramics. The results presented in this work show indubitably the importance of the nanopowders morphology on the material properties.

Highlights

Since its discovery during the Second World War, barium titanate (BaTiO3) has been extensively studied because of its excellent dielectric, ferroelectric, and piezoelectric properties providing new opportunities for a wide range of applications directed to the electronic devices industry [1, 2]
Scanning electron microscopy (SEM) investigation showed that cube-shaped nanoparticles with narrow size distribution and average dimension of 55 nm were formed after the hydrothermal treatment with stirring (Figures 1(a) and 1(b)), SEM investigation of the sample denoted BTNCs showed that the SEM analysis of the material prepared without stirring (Figures 1(c) and 1(d)) revealed the formation of faceted elongated particles with average diameter of 147 nm and aspect ratio around 3 suggesting the one-dimensional feature of the sample labelled BTNRs
All transmission electron microscopy (TEM) results are in accordance with the SEM analysis (Figure 1(d)) and force the idea that the BTNRs could be formed under hydrothermal conditions by a selfassembly oriented attachment mechanism

Summary

Introduction

Since its discovery during the Second World War, barium titanate (BaTiO3) has been extensively studied because of its excellent dielectric, ferroelectric, and piezoelectric properties providing new opportunities for a wide range of applications directed to the electronic devices industry [1, 2]. When choosing a synthesis method for 1D perovskite-type oxides it must be considered that this is capable of ensuring the complete control over the structure, size, and morphology for the enhanced functional properties at nanoscale preservation. In this view, the hydrothermal method is a very good approach, as it has been demonstrated that the structure, size, and shape– controlled BaTiO3 crystalline nanoparticles can be obtained by hydrothermal treatments of precursors at relatively low temperatures (

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