Effect of heat treatment on internal stress in barium titanate nanocube assemblies and their dielectric property

Hiroki Itasaka,Kyuichi Yasui,Koichi Hamamoto,Kazumi Kato,Ken-Ichi Mimura

doi:10.1063/5.0040765

Hiroki Itasaka, Kyuichi Yasui + Show 3 more

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https://doi.org/10.1063/5.0040765

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Abstract

Heat treatment is a key process to determine the dielectric properties of nanocrystalline barium titanate (BaTiO3) ceramics, which are a prospective candidate to realize further miniaturization of dielectric components in electric devices. Here, we use Raman spectroscopy and scanning microwave impedance microscopy to investigate the dependence of the internal stress and the relative permittivity of BaTiO3 nanocube three-dimensional assemblies on heat treatment temperature. We show that heat treatment in the temperature range from 700 °C to 1000 °C causes internal compressive stress in the nanocube assemblies without grain growth. The internal compressive stress is caused by formation of tight attachments between neighboring BaTiO3 nanocubes and of Ti-rich phases in the nanocube assemblies in the lower and higher temperature ranges, respectively. We also show that the relative permittivity of the nanocube assemblies at 3 GHz shows a positive correlation with the internal compressive stress. The result indicates that the internal compressive stress enhances the relative permittivity of BaTiO3 nanocubes.

Highlights

Barium titanate (BaTiO3) ceramics have been intensely studied for many decades owing to their wide range of applications, in particular multilayered ceramic capacitors (MLCCs)
We have found that the variation in the relative permittivity of the nanocube assemblies depends on heat treatment temperature in the range of 800 ○C to 900 ○C
Transmission and scanning transmission electron microscopy (TEM and STM) observations revealed that in scitation.org/journal/adv the temperature range, no grain growth occurs in BaTiO3 nanocube ordered assemblies, 14–16 implying that the change in the relative permittivity does not result from change in grain size

Summary

Introduction

Barium titanate (BaTiO3) ceramics have been intensely studied for many decades owing to their wide range of applications, in particular multilayered ceramic capacitors (MLCCs). No significant variation is observed in both the intensity ratio and standard deviation among the samples unheated and heated at ∼1000 ○C, whose result indicates that the heat treatments in this range caused no change in the Ba/Ti ratio in the nanocube assemblies.

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