Nanoparticles of the giant dielectric material, CaCu3Ti4O12 from a precursor route

TL;DR

This paper presents a low-temperature method to synthesize CaCu3Ti4O12 nanoparticles with controlled size, revealing how Cu(II) coordination changes affect microstructure and resulting in high dielectric constants suitable for electronic applications.

Contribution

It introduces a novel precursor route for producing CaCu3Ti4O12 nanoparticles with tunable size and microstructure, enhancing dielectric properties for potential device use.

Findings

Nanoparticles with sizes 30-200 nm were synthesized at 680°C.

High dielectric constant of up to 40,000 was achieved.

Microstructure and Cu(II) coordination depend on annealing temperature.

Abstract

A method of preparing the nanoparticles of CaCu3Ti4O12 (CCTO) with the crystallite size varying from 30 to 200 nm is optimized at a temperature as low as 680 1C from the exothermic thermal decomposition of an oxalate precursor, CaCu3(TiO)4(C2O4)8 ? 9H2O. The phase singularity of the complex oxalate precursor is confirmed by the wet chemical analyses, X-ray diffraction, FT-IR and TGA,DTA analyses. The UV Vis reflectance and ESR spectra of CCTO powders indicate that the Cu(II) coordination changes from distorted octahedra to nearly flattened tetrahedra (squashed) to square-planar geometry with increasing annealing temperature. The HRTEM images have revealed that the evolution of the microstructure in nanoscale is related to the change in Cu(II) coordination around the surface regions for the chemically prepared powder specimens. The nearly flattened tetrahedral geometry prevails for CuO4 in the near surface regions of the particles, whereas square-planar CuO4 groups are dominant in the interior regions of the nanoparticles. The powders derived from the oxalate precursor have excellent sinterability, resulting in high-density ceramics which exhibited giant dielectric constants upto 40,000 (1 kHz) at 25 1C, accompanied by low dielectric loss 0.07.