PbWO4‐III (a high‐pressure form)
PbWO4‐III (a high‐pressure form)
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DOI：
10.1107/s0567740876004214
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发表时间：
1976-03
期刊：
影响因子：
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通讯作者：
P. W. Richter;G. Kruger;C. Pistorius
中科院分区：
文献类型：
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作者：
P. W. Richter;G. Kruger;C. Pistorius
PbWO4-III, monoclinic, P21/n, a= 12.709 (5), b= 7.048 (3), c= 7.348 (3) A, fl= 90.57 (4), Z= 8, Dc= 9-19 g cm-3. Crystals were prepared under high pressure at high temperature in the presence of water. PbWO4-III is formally isomorphous with BaWO4-11, but the coordination number of both sets of Pb atoms is eight.Introduction. PbWO4 occurs in nature as tetragonal stolzite (PbWO4-I, scheelite-type) and monoclinic raspite (PbWO4-II, unique structure, not wolframite-type). PbWO4-II is 1.3% less dense than PbWO4-I (Shaw & Claringbull, 1955), and has not yet been prepared synthetically. PbWO4-11! exists above the pressure P (kbar)= 0.7+ 0.039 T (C)(T= 350-650 C), and is quenchable to normal pressure (Chang, 1971). Single crystals of PbWO4-III were prepared by sealing precipitated PbWO4-I with a small amount of distilled water in a thin-walled Pt capsule, treating this for 4h in a piston-cylinder device (Kennedy & LaMori, 1961) at 500 C, 32 kbar, and cooling slowly before release of pressure. Intensities were collected on a Philips PWll00 four-circle diffractometer in the oJ-20 mode with graphite-monochromated Mo Ks radiation. A roughly spherical crystal with radius 0.1 mm was used. Data
