Hybrid processing and anisotropic sintering shrinkage in textured ZnO ceramics

Abstract

We have studied the combined effects of the templated grain growth and magnetic alignment processes on sintering, anisotropic sintering shrinkage, microstructure development and texture in ZnO ceramics. Suspensions of 0-10 vol % ZnO template particles were slip cast in a 12 T rotating magnetic field. Sintering and texture characteristics were investigated via thermomechanical analysis and electron backscatter diffraction, respectively. Sintering as well as texture characteristics depend on template concentration. For the studied ZnO system, there is a critical template concentration (2 vol % in this study) above which densification is limited by the templates owing to constrained sintering. Below this limit, the densification is enhanced and the anisotropic shrinkage is reduced, which is attributed to densifying characteristics of the templates.

Low-field dynamic magnetic alignment and templated grain growth of diamagnetic PMN–PT ceramics

“…20 In ZnO, MA and TGG were combined primarily to increase texture quality by facilitating improved alignment of the larger template particles. 21 Apart from the ability to obtain biaxial alignment, the grain orientation distributions in these studies are comparable to results from MA or tape casting/TGG. Additionally, the use of high field (12 T) superconducting magnets in MA processing raises concerns regarding scalability of these techniques.…”

“…The use of TGG in conjunction with MA has been demonstrated previously in the Bi 4 Ti 3 O 12 and ZnO systems. 20,21 In Bi 4 Ti 3 O 12 , anisotropic templates were primarily used to facilitate biaxial (three-dimensional) alignment, in which case one direction was aligned by mechanical forces (slip casting), and a second direction was aligned magnetically. 20 In ZnO, MA and TGG were combined primarily to increase texture quality by facilitating improved alignment of the larger template particles.…”

FAST/SPS sintering of nanocrystalline zinc oxide—Part II: Abnormal grain growth, texture and grain anisotropy

“…Díaz-Chao et al [23] concluded that the crystallographic preferred orientation is a direct consequence of the needle-like morphology, which reoriented under the uniaxial pressure. Similar investigations about the sintering of needle-like ZnO particles also resulted into crystalline texture [20,43,57,68]. These particles may rotate under mechanical pressure into a direction perpendicular to it and finally align, which is an important mechanism for this formation of texture [69].…”

“…On the other hand, the particles may already be aligned during the casting process of the green body prior to sintering. This procedure is often referred to template growth [43] and may be realized via slip casting [68] or tape casting of platelet [22] and rod-like [20,43] crystallite. However, in the present work only isometric particles are initially present, which represents no good explanation for the occurrence of crystalline texture.…”

Fabrication of Ceramics with Highly Controlled Microstructures by Advanced Fine Powder Processing

“…Bi 3 TiNbO 9 planar particles with a biaxial orientation can be obtained by employing gravity and applying a magnetic field (Keskinbora K. et al, 2010;Gao Z.P. et al, 2015).…”