Decrease In Microstrain Research Articles

X-ray diffraction peak-broadening analysis of (La-M)2CuO4 high-Tc superconductors

An X-ray diffraction peak-broadening analysis of four oxides is described: La2CuO4 and La1.85M0.15CuO4 (M = Ca,Ba,Sr) high-Tc superconductors. The diffraction line profiles were fitted with a convolution of specimen and instrumental functions, and the specimen peakbroadening angular dependence was analyzed with the Warren-Averbach method. It was found that microstrains and incoherently diffracting domains are highly anisotropic. In the superconductors, stacking-fault probability increases with increasing Tc; microstrain decreases. In La2CuO4, different broadening of (h00) and (0k0) reflections is not caused by stacking faults; it might arise from lower crystallographic symmetry.

Stacking faults and microstrain in La 1.85M 0.15CuO 4 ( M = Ca, Ba, Sr) by analyzing X-ray diffraction line broadening

We obtained x-ray diffraction patterns for three oxides: La 1.85M 0.15CuO 4 ( M= Ca, Ba, Sr). The superconductors show zero-resistance T c values of 19, 28, and 36 K, respectively. Diffraction- line profiles were fit with a convolution of specimen and instrumental functions. The specimen line-broadening angular dependence was analyzed by the Warren-Averbach method of real Fourier coefficients. Stacking-fault probability increases with increasing T c; microstrain decreases.

Applications of X-ray Diffraction Crystallite Size/Strain Analysis to Seismosaurus Dinosaur Bone

AbstractRecently, the remains of a giant Cretaceous Sauropod (~150 My old) were discovered in the Morrison Formation west of Albuquerque, New Mexico. This dinosaur, tentatively named Seismosaurus, was found in an exceptional state of preservation. Although it has been known since the 180Q's that fossilized bone is often composed of the mineral apatite, very few studies have been conducted to characterize farther the fossilized material. In an effort to gain insight into the state of preservation and Hie processes occurring in the bone since deposition, apatite in bone from Seismosaurus was compared with that from a contemporary elk from the Jemez Mountains, New Mexico, and with well-crystallized mineral apatite using X-ray powder diffraction and profile analysis techniques. Crystallite size/strain analyses were conducted using the Scherrer equation, the Warren-Averbaca and single-line methods, and the Rietveld method using the program GSAS. Heating the contemporary elk bone produced a decrease in the full-width-at-half-maximum (FWHM) of the reflections in the diffraction pattern. This decrease in FWHM is due to a decrease in microstrain along with a minor increase in crystallite size. Results from crystallite size/strain analysis show that both Seismosaurus and contemporary elk bone crystallites are elongate parallel to the c-axis. However, Seismosaurus bone crystallites are larger (-20-65 nm) with less strain than the contemporary elk bone crystallites (-8-20 nm), suggesting that if elk bone is an appropriate analog, then Seismosaurus bone must have undergone recrystallization.

Study of photoconductive PbTe films by the method of variance analysis of X-ray diffraction profiles

Effective crystalline size and strain in 'as-grown' and annealed photoconductive PbTe films of various thicknesses ( approximately 2000 AA and greater) have been determined by the method of variance analysis of the X-ray diffraction line profiles. Photosensitivity measurements have been made on the same films and it has been observed that there is a decrease in photosensitivity and microstrain with increase in crystallite size. The crystallite size increases and microstrain decreases when the films are heat-treated at 200 degrees C but the photosensitivity is markedly increased. The effect is probably due to chemisorbed oxygen.

X-ray diffraction line broadening studies of Raney copper and nickel

X-Ray diffraction line broadening analysis has been used to determine crystallite sizes, microstrains and stacking fault probabilities in Raney nickel and Raney copper catalysts prepared by different methods. The data for the Raney catalysts were compared with those for ball-milled copper and nickel powders. Time and temperature of digestion of the Raney alloys affect the defect structures. The crystallite size in the (111) direction was mainly determined by the digestion temperature. On aging a highly active Raney nickel, a rapid decrease of microstrain was observed. This was followed by a steady growth in the (100) direction, while little change occurred in the (111) direction. Aging the catalyst and increasing the digestion time of the Raney alloy were shown to cause similar changes in defect structure. The microstrain and stacking fault probability were observed to be inversely related to crystallite size.