Phase diagram and Raman Imaging of Grain Growth Mechanisms in Highly Textured Pb(Mg1/3Nb2/3)O3-PbTiO3 Piezoelectric Ceramics

TL;DR

This study investigates grain growth mechanisms in textured PMN-PT ceramics using Raman imaging, revealing temperature-dependent growth phases and compositional variations, and proposes a phase diagram for these materials.

Contribution

It introduces a detailed analysis of grain growth mechanisms and compositional changes in textured PMN-PT ceramics using Raman imaging, and proposes a new phase diagram.

Findings

Two growth mechanisms identified: liquid I phase at lower temperatures and liquid II phase at higher temperatures.

Raman parameters correlate with composition and structural distortions.

Final ceramic structure closely matches the matrix composition.

Abstract

Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solution (PMN(1-x)-PTx) ceramics with 0 <x<1 have been prepared by homo-epitaxial templated grain growth (HTGG) using cubic PMN-PT single crystal seeds as templates and nanoparticles for thes ceramic matrix. Samples were prepared using the doctor Blade method and sintered in a controlled atmosphere. They were then analysed by DTA, TGA, optical/scanning electron microscopy, Raman spectroscopy and imaging. Relationships between Raman parameters such as band component or area versus composition (x) are proposed. Wavenumber and peak area shifts from the single crystal seed centre to periphery growth are assigned to compositional change. Representative medium to highly textured ceramics with Lotgering factors of ~0.7 and 0.9 were sintered at 1150 degrees C and 1200 degrees C, respectively, and studied by direct and smart Raman imaging. The Raman peak centre of gravity depends on the solid solution composition whereas peak intensity is correlated to the unit-cell distorsion and related short-range structure. Two different growth mechanisms are observed: below ~1200 degrees C, sharp corner and straight edged single crystal seeds develop through a liquid I phase at the crystal/matrix interface; at higher temperatures, the matrix is consumed and crystal growth develops in contact with a liquid II phase, through the help of the high PbO partial pressure. Smart Raman imaging shows that the final composition and structure is very close to that of the matrix. Formation of short-range ordered B/B' domains is expected. A phase diagram is proposed.