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The crystal growth, structure and Raman spectra of the Pr x Y 1−x Al 3 (BO 3 ) 4 (PYAB) single crystals are introduced. The experiments show that the characteristic lattice vibrational spectrum of the PYAB arises mainly from the internal vibrations of the BO 3 and AlO 6 groups, and that the rigidity of the lattice is mainly ascribed to the vibrations of B-O and Al-O bonds. For the Pr/YO 6 groups, there is no O 2− ion that is independent of the BO 3 and AlO 6 groups, and no new internal vibrational mode arises. Hence the characteristic lattice vibrational spectrum is not affected by the rare earth ions doped in the PYAB, and the ions can affect the external vibrations of the BO 3 and AlO 6 groups and improve the structural and optical quality of the crystals.

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Domain configurations and structures of ferroelectric KTa1−x NbxO3 crystals in both orthorhombic and tetragonal phases are studied by a polarizing microscope. It is found that the domain patterns vary in plates of different thicknesses. The domain evolution and new phase nucleation during the first‐order orthorhombic‐tetragonal‐cubic phase transitions with large thermal hysteresis are directly observed under polarized light. The emergence of a large number of microdomains upon cooling is revealed and discussed.