The following article by L. L. Wyman is reprinted from Fifty Years of Progress in Metallurgical Techniques, ASTM STP 430, 1968, contains information on the early role of ASTM Committee E-4 in the publication of the early Powder Diffraction File data cards and in the formation of the Joint Committee on Powder Diffraction Standards. In fact, Roy Wyman was probably the single most instrumental individual in obtaining the sponsorship by ASTM for the continued publication of the PDF up to 1969 when JCPDS became an independent corporation. Roy was on the Board of Directors of JCPDS from the time of its incorporation until his death in 1976. He was Treasurer of JCPDS from 1971 to 1974 and Chairman from 1974 to 1975. Committee E-4 is still active and is the Committee within ASTM which maintains Cooperative Society status with the JCPDS-ICDD.

Standard Reference Materials (SRM) are stable materials which have one or more properties certified by the National Bureau of Standards. A general introduction is given to the types of SRM's and their certification. SRM's for X-ray diffraction are described in detail, including their intended use and their certified and other properties. New SRM's are under consideration as quantitative standards, intensity and line shape standards, and materials properties standards.

An X-ray powder diffraction analysis has been performed on several samples from the naturally occuring patina of the Statue of Liberty. This work, which was conducted as a service to the National Park Service as part of the restoration activities for the Statue, was performed to assess the impact of acid deposition on the phase composition of the patina. Samples of the patina that were obtained from various locations on the copper skin of the Statue were found to consist primarily of the basic copper sulfate known as brochantite or CuSO4·3Cu(OH)2. Another less stable form of basic copper sulfate CuSO4·2Cu(OH)2 known as antlerite was also observed in samples taken from areas that are more exposed to the incoming weather in New York harbor. The presence of antlerite supports the contention that acid deposition is promoting undesirable changes in the phase composition of the patina. Analyses were also performed on patina samples that were taken from pieces of the Statue's copper skin that had been removed in the years 1905 and 1980. X-ray powder diffraction of the corrosion product on the 1905 sample showed that it consisted primarily of the stable brochantite phase, while the 1980 sample displayed both copper chlorides as well as the less stable antlerite. Both samples also contained cuprite (Cu2O) which appears to have formed prior to either of the sulfates.

Most modern X-ray powder diffraction work is carried out using the parafocusing powder diffractometer. The typical instrument employs a mechanical goniometer to control the basic geometric movements required for recording diffraction data. Modern trends toward high speed data acquisition and computerized analytical procedures make the need for a well designed and well maintained goniometer system increasingly critical. This paper reviews the mechanical design parameters of typical goniometer systems in light of their influence on the accuracy and precision obtainable in diffraction data. Data on typical vertical and horizontal goniometer systems are compared, along with bench tests using a state of the art “anti-backlash” gearing system. By examining the nature of the errors typically encountered in today's goniometers it becomes evident why the next major improvement will likely be in software rather than hardware.

Although forensic science is regarded with a certain amount of fascination and admiration by the general public, to the practising forensic scientist it is often associated with painstaking and frustrating examinations.

This is particularly so in the most traditional area of forensic science, namely that of contact evidence where the identification and comparison of minute samples may provide an important clue for the investigator and assist in the conviction or exoneration of an accused person.

Contact evidence may include hairs and other fibres, paint samples, glass fragments, stains, soils and other deposits. Modern instrumentation such as infra-red spectrophotometry, gas chromatography, atomic absorption spectroscopy and energy dispersive X-ray analysis now allows a relatively simple identification of the composition of these materials. However, these techniques are not necessarily directed towards the absolute determination of structure of materials and this is particularly so in the case of crystalline materials of forensic interest such as soil, mortar, brick dust and paint fillers. Although the techniques previously mentioned provide the basis of an elemental analysis this may not be of much assistance in a forensic approach where chemical structure is the basis of a scentific comparison.

The synthesis and unit cell refinement of two industrially important ferroelectric compounds with the tungsten-bronze structure are reported.

The ternary compound YAg0.4Ga1.6 has the CaIn2-type structure. The only variable positional parameter z was determined by graphical methods from visual observations of intensities on a Debye-Scherrer pattern. Cu or Ni substitutions for Ag also result in a ternary CaIn2-type structure.

Florencite-(Nd) [(Nd,Ce)Al3(PO4)2(OH)6], was first described by Milton and Bastron (1971) from fracture surfaces in weathered cherts of the Franciscan Complex, south of Sausalito in Marin County, California. Florencite-(Nd) occurred there as a moderate-brown pulverulent earthy material; individual crystals were not discernible under microscopic examination. A semi-quantitative spectrographic analysis showed the presence of Nd (3 wt. %) and Ce (0.5 wt. %). No powder data for florencite-(Nd) exists in the current powder diffraction file.

Complete X-ray powder data is recorded from type specimens of the minerals nissonite and waylandite. Debye-Scherrer films of 114.59 mm diameter were measured with an automated densitometer. A wide step width of 0.08°2θ was required, because the average reflection width at half height was 0.5°2θ. The 2θ positions and relative intensities of the reflections were calculated from a negative second derivative function based upon a five point curve.

The following new or updated patterns are submitted by the JCPDS Research Associateship at the National Bureau of Standards. The patterns are a continuation of the series of standard X-ray diffraction powder patterns published previously in the NBS Circular 539, the NBS Monograph 25, and in this journal. The methods of producing these reference patterns are described in this journal, Vol. 1, No. 1, p. 40 (1986).

The data for each phase apply to the specific sample described. A sample was mixed with one or two internal standards: silicon (SRM640a), silver, tungsten, or fluorophlogopite (SRM675). Expected 2-theta values for these standards are specified in the methods described (ibid.). Data, from which the reported 2-theta values were determined, were measured with a computer controlled diffractometer. Computer programs were used to locate peak positions and calibrate the patterns as well as to perform variable indexing and least squares cell refinement. A check on the overall internal consistency of the data was also provided by a computer program.