The linear muffin-tin-orbital method based on the density-functional theory and the semi-empirical method of the Intermediate Neglect of the Differential Overlap based on the Hartree–Fock formalism are used for the supercell study of the F centers in cubic and orthorhombic ferroelectric KNbO3 crystals. Two electrons are found to be considerably delocalized even in the ground state of the defect...

The decomposition of the Ethiopian Kenticha tantalite ore was studied using the KOH fusion and H2O leaching system at 400 0C for a 1 h reaction time. The experimental results obtained showed that 27 wt% of Ta2O5 was mainly transformed into insoluble KTaO3, not to be KNbO3, and as well, into the dissolved liquor containing 94.73 vol% of Nb2O5 and 75.80 vol% of Ta2O5. The observations, supported ...

In view of serious environmental concerns with traditional Pb-based piezoelectrics, the search for new Pb-free alternatives has intensified recently. A thorough investigation of structure-property relationships in Pb-free piezoelectrics is desired in order to design new material compositions with high electromechanical properties that can be operated over a broader range of conditions. Recent a...

Nonlinear second-harmonic generation (SHG)microscopy has become a commonly used technique for investigating interfacial phenomena(Kemnitz et al., 1986; Shen, 1989) and imaging biological samples.(Moreaux et al., 2000) Different non-centrosymmetric nanometric light sources have been recently studied in this context, e.g. organic nanocrystals.(Shen et al., 2001; Treussart et al., 2003) For those ...

Due to the toxic nature of PbO in Pb(Zr,Ti)O3 (PZT), the most common type of piezoceramic, many studies on lead-free materials are being conducted worldwide (Röedel et al., 2009). One of the most studied groups of lead-free ferroelectric materials is based on a solid solution of potassium sodium niobate, K0.5Na0.5NbO3 (KNN) (Jaffe et al., 1971; Kosec et al., 2008). However, activity in attempts...