Thermal expansion anisotropy and acoustic emission of NaZr2P3O12 family ceramics

Srikanth, Varanasi ; Subbarao, Eleswarapu C. ; Agrawal, Dinesh K. ; Huang, Chi-Yuen ; Roy, Rustum ; Rao, Gutti V. (1991) Thermal expansion anisotropy and acoustic emission of NaZr2P3O12 family ceramics Journal of the American Ceramic Society, 74 (2). pp. 365-368. ISSN 0002-7820

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Most members of the NaZr2P3O12 (NZP) family possess low, near zero, overall thermal expansion coefficients. However, they also exhibit anisotropy of axial thermal expansion. Some compounds have opposite anisotropy; for example, the a parameter of CaZr4P6O24 contracts on heating and that of SrZr4P6O24 expands, while the c parameter expands for the Ca compound and contracts for the Sr compound. The anisotropy of the axial thermal expansion of these materials is believed to induce microcracking. The acoustic emission method was employed here to detect microcracking in ceramics due to the axial thermal expansion anisotropy. Acoustic signals were observed during cooling of the Ca and Sr compounds from 500° C, and Na and K compounds from 600° C. On the other hand, no acoustic emission signal is detected in Ca0.5Sr0.5Zr4P6O24 ceramics, in which the lattice parameters a and c remain nearly unchanged in the temperature range of room temperature to 500° C. Thus, a direct correlation between microcracking of ceramics and their anisotropic axial thermal expansion coefficients was established by employing acoustic emission monitoring techniques.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons.
Keywords:Zirconium; Phosphorus Oxide; Thermal Expansion; Acoustic Emission; Microcracking
ID Code:50478
Deposited On:25 Jul 2011 11:06
Last Modified:25 Jul 2011 11:06

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