Crystal growth of ferroelectric and ferroelastic K3[Nb3O6|(BO3)2] and crystal structure of the room temperature modification

Abstract

Abstract The anhydrous potassium niobate borate K3[Nb3O6|(BO3)2] has been grown from potassium borate flux to crystals of good optical grade and dimensions of up to 6×6×20 mm3. Incorrectly described earlier as trigonal P31m, K3[Nb3O6|(BO3)2] normally forms multidomain crystals at room temperature, composed of three different orientation states. The reported crystal structure of the room-temperature modification of K3[Nb3O6|(BO3)2], determined using a single-domain crystal, shows that the real symmetry is orthorhombic with space group P21 ma (No. 26) (a = 17.506(2) Å, b = 15.162(3) Å, c = 3.968(4) Å, Z = 4, Dx = 3.845 g/cm3, μ(MoKα ) = 4.122 mm−1, R(F) = 0.030 for 2752 unique reflections (I > 4σ(I)).