Growth of Silver Niobate Single Crystals and Their Dielectric Properties

抄録

The ferroelectric silver niobate (AgNbO₃) single crystals were grown using two kinds of crystal growth methods, and their dielectric properties were investigated. At first, the pure AgNbO₃ single crystals were grown using a conventional flux method with a AgCl solvent. Using this method, the AgNbO₃ single crystals with a size of 5 mm cube were obtained. The dielectric measurement of the AgNbO₃ crystals indicated the two additional dielectric maximums of 460°C and 520°C as well as some dielectric peaks reported in the AgNbO₃ ceramics. Thus, these two additional peaks were investigated using an in-situ domain observation. As a result, this observation revealed that these two peaks at 460°C and 520°C originated from the melting behavior of the residual AgCl (m.p.=455°C) in the crystals. To study an intrinsic dielectric property of the AgNbO₃ crystals, the impurity-free single crystals must be required. Fortunately, it was found that the AgNbO₃ crystals completely melted above 1200°C, and from these liquid phase, the AgNbO₃ crystals with their stoichiometric composition were formed with decreasing temperature. Thus, we developed this new crystal growth technique from the stoichiometric melts for the AgNbO₃ crystals, and named as a slow cooling method. Finally, we obtained the impurity-free AgNbO₃ crystals with sizes of around 3 mm cube. Using these crystals, their dielectric properties were investigated.