As part of a study of the long‐term operation of solid‐oxide fuel cells, three (Mn,Co,Cr)3O4 samples have been synthesized and characterized. X‐ray and neutron diffraction patterns from the powder samples at room temperature were measured and the data were co‐refined. The neutron data were indispensible in locating Mn, Co and Cr within the crystallographic unit cell with their respective atomic occupancies. Two of these samples have been identified as cubic Mn0.76Co0.58Cr1.66O4 and Mn1.28Co1.72O4. The third is a two‐phase sample containing cubic Mn1.66Co1.34O4 and tetragonal Mn2.05Co0.91O4 in a 59.1 (6):40.9 (6)% mass fraction ratio. Cr, which might be introduced from reaction with chromia during oxidation of interconnect materials, exhibits a preference for the octahedral site rather than the tetrahedral site. Without Cr, Mn dominates the octahedral site.

The Neutron Scattering Laboratory at Serpong is equipped with three diffractometers: a powder diffractometer (PD), a four circle diffractometer/texture diffractometer (FCD/TD) and a high resolution powder diffractometer (HRPD). The powder diffractometer (PD) was the first instrument installed (1987) by JICA/Japan and is situated in the reactor experimental hall (XHR) of the multi-purpose reactor (RSG) GA Siwabessy. The two others were installed in 1992 under phase III of the Sumitomo project, together with other neutron scattering instruments. In 1995 the PD instrument was modified to allow for residual stress measurements (RSM) in collaboration with the Japan Atomic Energy Research Institute (JAERI). The detailed activities of this instrument are explained in elsewhere in this issue. High resolution powder diffractometerThe high resolution powder diffractometer (HRPD) is a versatile diffractometer to study both crystallographic and magnetic structures of powder samples. Since X-ray diffraction is rather insensitive to light atoms such as hydrogen and oxygen, neutron diffraction is indispensable for the structure determination of materials containing such light elements. Furthermore, neutrons have an inherent magnetic moment that enables probing many kinds of magnetic structures ranging from colinear-commensurate to incommensurate configurations.The high resolution powder diffractometer (HRPD) is installed at the second neutron guide (NG2) in the neutron guide hall (NGH) about 71 meters away from the reactor core. It consists of a monochromator, collimators, a sample table, and a multicounter system. The monochromator drum has three exits corresponding to three different take-off angles: 2θ M = 41.5°, 89°, and 130°. At present the instrument is set for 2θ M = 89°. Figures 1 and 2 show the instrument and the schematic diagram of HRPD, respectively.At the beginning, a pyrolitic graphite PG(004) focusing monochromator system comprised of five PG(004) single crystals provided a focused neutron beam having a wavelength of 2.352 Å. Although two PG(002) filters had been inserted in front of the sample with the consequence of reducing the beam intensity, higher order peaks were still apparent in the diffraction pattern, which confused the analysis. Later on, to overcome this problem, a hot pressed germanium single crystal replaced the PG monochromator [1] under a bilateral cooperation between JAERI and BATAN. The Ge(331) single crystal was pressed up to 70 kgcm −2 during heating at 850°C for one hour to increase the mosaic spread. Although the Ge(331) Figure 1. The HRPD instrument.Figure 2. Schematic diagram of HRPD.

The measurements of neutron diffraction patterns of commercially product and 10 hour mechanically milled cathode material lithium cobaltites (LiCoO 2 ) have been performed. Rietveld analysis using FullProf does not show the change of crystal structure due to milling process, but the diffraction pattern has a lower intensity and the diffraction-line was broadening. The results of line-broadening study on milled sample using Rietveld methods detected that the microstrain was occurred in the sample with value 0.127080(35) % and the average crystallite size was 424.78(20) Å.

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