ISSN:
1551-2916
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Maschinenbau
,
Physik
Notizen:
Pressureless-sintered TiO2-excess BaTiO3 (BT) ceramic doped with Na2O (as an acceptor oxide) has been investigated for the inhibition of platelike (111) twin grains and the associated microstructure development. Solid-state reaction between the Na2O dopant and the excess TiO2 of the nonstoichiometric BaTiO3 powder during sintering has resulted in the formation of orthorhombic Na4TiO4(N4T) at temperatures of ≤1215°C. Enhanced densification is due to a liquid-phase sintering mechanism, where the liquid eutectic is generated by reacting the excess TiO2 and the trace impurities of SiO2 and Al2O3 with the Na2O dopant. Suppression of the abnormally large, platelike grains occurs at a critical acceptor concentration of ∼0.50 mol% Na2O when sintering is conducted at 1215°C. The inhibition mechanism is associated with the secondary phases, whose formation gradually modifies the initially TiO2-excess powder toward the stoichiometric composition. The corresponding sintered microstructure is analyzed using both scanning and transmission electron microscopy. The second-phase precipitates of Na4TiO4, which are located intragranularly and intergranularly in the tetragonal BaTiO3 matrix grains, exhibit the following crystallographic orientation relationships: [110]BT// [100]N4T, (1〈inlineGraphic alt="inline image" href="urn:x-wiley:00027820:JACE2155:JACE_2155_mu1" location="equation/JACE_2155_mu1.gif" extraInfo="missing"/〉1)BT// (010)N4T, and (112)BT// (001)N4T.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1151-2916.2000.tb01529.x
