Thermal effects on mechanical grinding-induced surface texture in tetragonal piezoelectrics
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The effect of temperature on grinding-induced texture in tetragonal lead zirconate titanate (PZT) and lead titanate (PT) has been investigated using in situ x-ray diffraction (XRD) with an area detector. In contrast with previous results on electrical poling, mechanically-ground PT and soft PZT materials retain strong ferroelastic textures during thermal cycling, even after excursions to temperatures slightly above the Curie temperature. The relationship between the residual stresses in the surface region, caused by grinding, and those resulting from domain wall motion is elucidated by in situ texture measurements obtained during thermal cycling.
I. INTRODUCTION
We have previously determined the effect of temperature on ferroelastic textures, notably the electrical polinginduced textures in tetragonal lead zirconate titanate (PZT) and lead titanate (PT) materials.1 In this previous paper, we suggested that changes in the internal stresses caused by interactions between neighboring grains of differing orientation can provide a driving force for ferroelastic domain walls to migrate to more favorable positions as the tetragonality and the elastic constants both decrease with increasing temperature. The texture related to ferroelastic domain switching of tetragonal zirconias was previously investigated by Bowman.2 The objective of this paper is to examine whether there are any effects caused by interaction between the internal stresses that we educed in the earlier work, and other stresses that can be applied to the specimen. We approach this by studying thermal effects of mechanical grinding on the surface textures of the same PZT and PT materials. Grinding is a process that removes surface material, and can lead to residual stress in the near-surface layers of the remaining workpiece. In a ferroelastic material, this residual stress can induce near-surface preferred orientations due to a bias in the fractions of differently oriented ferroelastic domains.2–8 Virkar and Matsumoto3 observed that, upon grinding, the intensity of the (002) peak of tetragonal zirconia increases while that of the (200) peak decreases, without the formation of a monoclinic phase. They explained the changes in intensities of
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Address all correspondence to this author. e-mail: [email protected]. DOI: 10.1557/JMR.2007.0355 J. Mater. Res., Vol. 22, No. 10, Oct 2007
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the (002) and (200) peaks by ferroelastic domain switching. Similar results on grinding have been found in PZT materials.4,5 In a study of the state of stress in the ground surface region, Li et al.6 proposed that the biaxial compressive stress parallel to the sample surface can induce a texture in which most domains are oriented with their c-axes normal to the sample surface.
II. EXPERIMENTAL PROCEDURES
Our materials were a commercial soft PZT (Piezo Technologies K350, Indianapolis, IN) and PT (Piezo Technologies Nova 3B), produced by sintering. Samples were sliced in the form of thin rectangular bars and the typical d
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