Porous Li 0:06 (Na 0:5 K 0:5 ) 0:94 NbO 3 (LNKN-6) ceramics with different pore volumes have been prepared using preceramic powder and phenol resin fiber (KynolÔ) as a pore former. It was confirmed that the porous ceramics synthesized by the ''twostage firing method'' suppressed the loss of alkali elements from the porous body during heat treatment. The porous LNKN-6 ceramics were then converted to LNKN-6/KNbO 3 composites through soaking and heat treatment using a sol-gel precursor source composed of KNbO 3 to form 3 -3-type composites. The microstructure, dielectric, and piezoelectric properties of the porous LNKN-6 ceramics and LNKN-6/KNbO 3 composites were characterized and compared. The LNKN-6/KNbO 3 composites had a hollow structure whose pores in the region near the surface were filled and coated with KNbO 3 precipitates; however, a large amount of residual air was trapped in the pores inside the composites. As a result, the LNKN-6/KNbO 3 composites fabricated using 30 vol % KynolÔ showed an enhanced piezoelectric voltage output coefficient (g 33 ) of 63:0 Â 10 À3 VÁm/N, compared with monolithic LNKN-6 ceramics having a g 33 of 30:2 Â 10 À3 VÁm/N.

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Control of heterointerfaces in advanced composite materials is of scientific and industrial importance, because their interfacial structures and properties often determine overall performance and reliability of the materials. Here distinct improvement of mechanical properties of alumina-matrix tungsten-carbide composites, which is expected for cutting-tool application for aerospace industries, is achieved via interfacial atomic segregation. It is found that only a small amount of Zr addition is unexpectedly effective to significantly increase their mechanical properties, and especially their bending strength reaches values far beyond those of conventional superhard composite materials. Atomic-resolution STEM observations show that doped Zr atoms are preferentially located only at interfaces between Al2O3 and WC grains, forming atomic segregation layers. DFT calculations indicate favorable thermodynamic stability of the interfacial Zr segregation due to structural transition at the interface. Moreover, theoretical works of separation demonstrate remarkable increase in interfacial strength through the interfacial structural transition, which strongly supports reinforcement of the interfaces by single-layer Zr segregation.

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