This research summarizes the analytical and experimental results of heat-transfer processes influence on defects formation during sapphire crystal growth by horizontal directed crystallization method(HDC).The shape of...This research summarizes the analytical and experimental results of heat-transfer processes influence on defects formation during sapphire crystal growth by horizontal directed crystallization method(HDC).The shape of solid-melt interface significantly influences the process of sapphire crystals growth by this method.We receive the Stefan problem solution for sapphire crystals growth.It allows investigating the crystal growth process and the related factors(thermal stresses on different stages of growth process),their influence on defects formation.We investigate the main reasons for the formation of defective structures of the solid phase of sapphire crystals and the influence of thermal unit construction,the crystal geometry on the quality of the resulting sapphire crystal.We study the structure formation process,impurity distribution,and the nature of the defects in the crystal during it growth.展开更多
The calculations of low-energy phonon dispersion relations in lead zirconate(PZ)have been carried out using the Vaks model.This model takes into account only five low-energy phonon modes and their interactions.It has ...The calculations of low-energy phonon dispersion relations in lead zirconate(PZ)have been carried out using the Vaks model.This model takes into account only five low-energy phonon modes and their interactions.It has been shown that this model allows to achieve good agreement not only between calculated and experimental transverse acoustic phonon dispersion but also between their temperature dependences.It has been shown 5-mode system,which describes low-energy phonon dispersion in PZ,is close to unstable state.Even a little change of interaction parameter can lead to lattice instability with nonzero wave vector qcrit.Wave vector qcrit could have any value,including irrational one.In this case,system will undergo an incommensurate phase transition.展开更多
基金The authors thank the Slovak partners(CEIT a.s.)for cooperation.The study was carried out with the financial support of the Russian Foundation for Basic Research,Project No.19-52-53026.
文摘This research summarizes the analytical and experimental results of heat-transfer processes influence on defects formation during sapphire crystal growth by horizontal directed crystallization method(HDC).The shape of solid-melt interface significantly influences the process of sapphire crystals growth by this method.We receive the Stefan problem solution for sapphire crystals growth.It allows investigating the crystal growth process and the related factors(thermal stresses on different stages of growth process),their influence on defects formation.We investigate the main reasons for the formation of defective structures of the solid phase of sapphire crystals and the influence of thermal unit construction,the crystal geometry on the quality of the resulting sapphire crystal.We study the structure formation process,impurity distribution,and the nature of the defects in the crystal during it growth.
文摘The calculations of low-energy phonon dispersion relations in lead zirconate(PZ)have been carried out using the Vaks model.This model takes into account only five low-energy phonon modes and their interactions.It has been shown that this model allows to achieve good agreement not only between calculated and experimental transverse acoustic phonon dispersion but also between their temperature dependences.It has been shown 5-mode system,which describes low-energy phonon dispersion in PZ,is close to unstable state.Even a little change of interaction parameter can lead to lattice instability with nonzero wave vector qcrit.Wave vector qcrit could have any value,including irrational one.In this case,system will undergo an incommensurate phase transition.
