The Double Borates Ba3Ln(BO3)3, Ln=La–Lu, Y

New compounds of the compositions Ba3Ln(BO3)3, Ln=La–Lu, Y were obtained in the ternary systems BaO–Ln2O3–B2O3. Single crystals were grown for Ba3Yb(BO3)3. X-ray diffraction analysis showed a hexagonal structure with space group P63cm and lattice parameters a=9.411(1), c=17.481(5) ?, Z=6. The compounds with Ln=Dy–Lu, Y also crystallize in the space group P63cm. New temperature data on melting points and unit-cell dimensions were obtained for each compound. The borates with Ln=La–Tb are isostructural and crystallize in the space group R . Optical second harmonic generation (SHG) measurements of laser radiation showed that Ba3Yb(BO3)3 has type I phase transition. By investigation of the crystals of the double borate Ba3Yb(BO3)3 it was established that the compound possesses a pyroelectric effect.