Optical and electronic properties of some nely rare earth-doped lead sodium apatites

Abstract Single crystals of the anion-deficient apatite of formula Pb 8 Na 2 (PO 4 ) 6 O 2 as well as rare earth-doped compositions of the type Ln x Pb 8−x Na 2 ( PO 4 ) 6 O 2− x 2 O x 2 with Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er have been grown by the Czochralski technique. All crystallize in the P6 3 m space group of apatite with c h about 7.20 A and a h about 9.73 A. Transmission, excitation, and fluorescence spectra were obtained on many single crystals and are discussed. Anomalous dielectric behavior indicating ionic conduction is also presented. It is further shown that the often quoted “lead orthophosphate of apatite structure, Pb 3 (PO 4 ) 2 ” is actually not pure lead phosphate but rather a sodium stabilized apatite of the composition Pb 8+x Na 2−x ( PO 4 ) 6 O 2− x 2 O x 2 .