A diamond cell for x-ray diffraction studies at high pressures

A high pressure X-ray powder camera has b een constructed.The instrumen t has been found to be usefu l for rout ine X-ray work, using molybdenum radiation, to pressures of approximately 60 kilobars.Previously repo l ted transitions have been observed in s ilver iodide, potassium iodide, bismu th , and t hallium.The high pressure forms and lattice parameters were found to be: AgI-f.c.c. (NaCI ty pe), ao = 6.067A; KI-s.c.(CsCI type), ao = 4.093 A; Tl-f.c.c.(NaCl type) , ao = 4.778 A; Bi structure not d etermined .These data confirm previous reports en the high press ure forms of AgI and KI.D ata on T l and B i are al)parently reported for the first time.The high pressure mod ifi cations were stud ied at the fo ll owing approximate press ures whieh are not ind icative of the point where t he transition occurs: AgI-3.3 kilobars, KI-20 kilobars, Bi-28 kilobars, and Tl-60 kilobars-;lThe press ure limi t to which t he unit can be used s uccessfully has not been ascer tained .It is beli eved to be much hi gher than the pressures report.ed.The present instrument is capable of produ cing powder diffraction patterns of materials of relatively high scattering power, giv ing data to 20 = 35°.High background on t he X-ray powder patterns is believed to arise from scat tering by t he diamonds.This background may obscure weak diffraction rings.This effect may be reduced by sc reening, monochromatization, and other improvements in experimental technique.