Abstract
BaO-Sm 2 O 3 –5TiO 2 (BST) added by Al 2 O 3 was prepared by solid-state reaction method. The main phase is Ba 3.99 Sm 9.34 Ti 18 O 54 of orthorhombic tungsten bronze structure, and the secondary phase is Ba 1.18 Al 1.90 Ti 6.09 O 16 of tetragonal structure, which has two types of grains: one is grey and cubic, and the other is white and quasi-rectangular. Microstructure was characterized by XRD, SEM, and Raman spectra. Micromechanical properties of different phases were assessed by nanoindentation and micro-scratch tests with Berkovich indenter. Volume fractions of different phases obtained by statistical analysis of grid indentation are in good agreement with those obtained by XRD analysis. Vickers hardness method is more appropriate for the determination of the fracture toughness of dielectric ceramics. BST ceramic without addition of Al 2 O 3 has better mechanical properties than BST-A with addition of Al 2 O 3 , indicating that addition of Al 2 O 3 impairs the micromechanical properties of dielectric ceramics.
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