DOUBLE BORATES Ba3Ln(BO3)3, Ln=La-Lu, Y

摘要

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. XRD analysis showed a hexagonal structure with space group P63cm and lattice parameters a=9.411(1), c=17.481(5) angstroms, 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-3. 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. 9 refs.