Effect of Grain Size on Microcracking in Lead Titanate Ceramics

Fabrication and dielectric properties of lead titanate nanocomposites

“…4(a-c)). The different microstructure evolution of PT nanocomposites confirms the importance of the processing method including the morphological characteristics of the dispersed phase, consistent with other works [32,35]. Whilst the grain size of both nanocomposites is approximately the same, the density and microstructure of PT samples sintered at higher temperatures indicated that the composite method of PT matrix reinforced with PT nanofibers was preferable for obtaining dense PT ceramics.…”

“…4. It is seen that a uniform grain shape of typical perovskite ceramics [9,30,31] is observed, with sizes in the range of 0.2-2.8 m. It should be noted that the average grain size of both PT nanocomposites is <1.7 m, which is less than the critical value of 3 m [11,32,33] and gives rise to a volumetric percentage enough to buffer the anisotropic stress caused by the phase transition [32]. Here, it is believed that PT nanodispersoids with random orientations result in lower internal stress in composite samples because they compensate the anisotropy of thermal expansion coefficients.…”

Effects of SiC nanofibers addition on microstructure and dielectric properties of lead titanate ceramics

“…A distribution of SiC fibers in a matrix may decrease the sintering rate by inducing tensile mean stress in the matrix [27,28]. The effects are less pronounced for a PT matrix, wherein the tensile mean stress approaches the sintering potential, resulting in substantial retardation of sintering, as observed experimentally.…”

Statistical Properties of Residual Stresses and Intergranular Fracture in Ceramic Materials

“…These internal stresses, induced by the anisotropy of thermal contraction between adjacent grains, can promote spontaneous cracking along grain facets (e.g., Clarke, 1964;Matsuo and Sasaki, 1966;Davidge and Green, 1968;Kuszyk and Bradt, 1973;Cleveland and Bradt, 1978;Evans, 1978;Blenctell and Coble, 1982;Yu and Evans, 1985;Fredrich and Wong, 1986). The occurrence ofmicrocracking has been found to depend on the scale of the microstructure in that there exists a critical grain size in single-phase systems below which grain boundary microfracture is essentially suppressed (Matsuo and Sasaki, 1966;Evans, 1978;Rice and Pohanka, 1979). In addition, Prior studies have identified the existence of a critical grain size beyond which total loss of material integrity occurs -Contributed by the Applied Mechanics Division of THE AMERICAN SocIETY QF MECHANICAL ENGINEERS for publication in the ASME JOURNAL OF APPLIED MECHAN!cs.…”