The phase transition of PbHPO4

X-ray powder diffraction study of PbHPO4 was carried out under hydrostatic conditions at room temperature. We could not detect any difference in the diffraction patterns except peak shift with increasing pressures up to 6 GPa. By further compression, a new pressure-induced phase appears at about 6.5 GPa. We have determined that the structure of this high-pressure phase has a possible space group of Pmmm, and which is stable up to 17 GPa. During decompression process, this phase is converted back to the original phase II at 0.7 GPa. (c) 2005 Elsevier B.V. All rights reserved.