Authors O.V. Karban, O.M. Kanunnikova, E.N. Khazanov, A.V. Taranov
Month, Year 09, 2015 @en
Index UDC 546.621/623:17
Abstract In the studied segnetoelectrical Ва-W-Ti-O ceramics, compacted under different conditions of pressure and ultrasound action with subsequent sintering at 1623 K, structure and composition of interface regions vary in a nonmonotonic way. The chemical composition was analyzed by the X-ray photoelectron spectroscopy. The structure of the ceramics interface regions and their specimen-average characteristics were investigated by the heat pulse method. In the ceramics studied different boundary types are observed: boundaries between agglomerates, between grains in the agglomerates, and boundaries between areas of coherent scattering. However, a satisfactory agreement between the theoretical calculations and the experimental temperature dependences of nonequilibrium phonon scattering is observed only in the case when R is the size of grains (particles) forming the agglomerates. Accelerated tungsten diffusion to the grain surface during sintering is determined by ultrasound action activation in process of powder consolidation. Increasing the pressure during dry static compacting and exposure to ultrasound result in the formation of complex structure of fragments and boundaries between them increase the acoustic density and lead to a decrease in the intergranular boundary thickness to values that are sometimes comparable to the lattice constant of the boundary material. The optimum boundary structure is found in specimens compacted at a pressure of about 700-800 MPa which allows the formation of an interface region with prevailing content of isotropic structure.

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Keywords Ва-W-Ti-O ceramics; interface regions; XPS; phonon spectroscopy.
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