The geometrical structure optimization,band structure,density of states,and charge density contour of potassium niobate(KNbO_(3))in the bulk[100]direction and(100)surface are calculated and analyzed using density func...The geometrical structure optimization,band structure,density of states,and charge density contour of potassium niobate(KNbO_(3))in the bulk[100]direction and(100)surface are calculated and analyzed using density functional theory.The elastic constants,which can describe the bonding characteristics and structural stability,are also computed,and the dielectric function,which can be used to calculate all the other optical properties of the material,is evaluated.Local density approximation functional analysis using CASTEP software is also employed.Several similarities and differences are observed in the properties of the KNbO_(3) bulk and surface.Almost all of the calculated results for the bulk sample are twice those of the surface sample.The results are consistent with the experiment.展开更多
Potassium tantalate niobate （KTa1-xNbxO3, KTN） crystals with different dimensions and quality situations were grown by Czochralski method. Crystal growth process and morphology properties of KTN are presented in thi...Potassium tantalate niobate （KTa1-xNbxO3, KTN） crystals with different dimensions and quality situations were grown by Czochralski method. Crystal growth process and morphology properties of KTN are presented in this paper. It was found that some defects, such as bubble, inclusion, crack, dislocation etc., can all appear if the crystal is grown in an improper condition. The character and formation mechanism of such defects in macro growth are discussed. We consider that the CO2, which was not released absolutely during the sintering process and dissolved in the melt, led to bubbles. The composition of the inclusion caused by high pulling and rotation rates is KTN polycrystalline. The crack and dislocation in KTN crystal mainly come from improper temperature field. Etching and high-resolution X-ray diffraction （HRXRD） experiment results indicate that the central area is the defects concentrated.展开更多
文摘The geometrical structure optimization,band structure,density of states,and charge density contour of potassium niobate(KNbO_(3))in the bulk[100]direction and(100)surface are calculated and analyzed using density functional theory.The elastic constants,which can describe the bonding characteristics and structural stability,are also computed,and the dielectric function,which can be used to calculate all the other optical properties of the material,is evaluated.Local density approximation functional analysis using CASTEP software is also employed.Several similarities and differences are observed in the properties of the KNbO_(3) bulk and surface.Almost all of the calculated results for the bulk sample are twice those of the surface sample.The results are consistent with the experiment.
文摘Potassium tantalate niobate （KTa1-xNbxO3, KTN） crystals with different dimensions and quality situations were grown by Czochralski method. Crystal growth process and morphology properties of KTN are presented in this paper. It was found that some defects, such as bubble, inclusion, crack, dislocation etc., can all appear if the crystal is grown in an improper condition. The character and formation mechanism of such defects in macro growth are discussed. We consider that the CO2, which was not released absolutely during the sintering process and dissolved in the melt, led to bubbles. The composition of the inclusion caused by high pulling and rotation rates is KTN polycrystalline. The crack and dislocation in KTN crystal mainly come from improper temperature field. Etching and high-resolution X-ray diffraction （HRXRD） experiment results indicate that the central area is the defects concentrated.
