The system of phosphates Ca9−xPbxHo(PO4)7 were obtained by solid-state reaction and were found to be isotypic with whitlockite-type β-Ca3(PO4)2 (polar space group R3c). The crystal structure encloses five crystallographic sites M1–M5 different in size and oxygen coordination. The unit-cell parameters were determinate using Le Bail decomposition. Rietveld method structural refining showed that Ho3+ ions are located statistically with calcium in M1 and M2 sites, while Pb2+-ions are located in the M3 site. Examination of optical second-harmonic generation evidences non-linear optical activity and confirms polar space group R3c. Structural mechanisms and dielectric features of phase transitions are strongly influenced by the exact distributions of atoms over the crystallographic sites.

New phosphates Ca9–xPbxEu(PO4)7 were obtained by solid state reaction techniques at 1213–1253 K in air atmosphere and were found to be isotypic with whitlockite-type β-Ca3(PO4)2. The unit cell parameters were determinate using Le Bail decomposition. Rietveld method structural refining showed that Eu3+ ions are located statistically with calcium in M1, M2, and M3 sites, whereas Pb2+-ions are preferentially located in the M3. Examination of optical second harmonic generation evidences nonlinear optical activity and confirms polar space group R3c.