Boris Paretzkin

Crystal chemistry and phase equilibria studies of theBaO(BaCO3)R2O3CuOsystems. IV. Crystal chemistry and subsolidus phase relationship studies of the CuO-rich region of the ternary diagrams,R =lanthanides

Abstract In theBaO(BaCO3) R2O3 CuOsystems, whereR =lanthanidesand yttrium, general trends of phase formation, solid solution formation, and phase relationships are correlated with the ionic size ofR.In air at 950°C the phase relationships in the CuO-rich region of these ternary diagrams progressively change from the La system through the Nd, Sm, Eu, Gd, Y, Ho systems to the Er system. First, the La system has the greatest number of ternary compounds. Second, the superconductor material,Ba2RCu3O6+x,exhibits a solid solution ofBa2−zR1+zCu3O6+xfor the first half of the lanthanide elements with a range of formation which varies with the ionic size ofR.Third, a trend is observed regarding the tie-line connections betweenBaR2CuO5, CuO, the phasesBa2−zR1+zCu3O6+x, and the binary phaseR2CuO4orR2Cu2O5.For the first half of the lanthanides, except for La, a compatibility join is found to connectR2CuO4and the tetragonal end member of theBa2−zR1+zCu3O6+xphase. In systems whereRhas a smaller ionic size,R =Euand beyond, the tie-line connection switches to join theBaR2CuO5phase and the CuO phase. ForR =Dyand beyond, the binary phaseR2CuO4is replaced by the binary phaseR2Cu2O5.

Methods of Producing Standard X-Ray Diffraction Powder Patterns

Patterns useful for identification are obtained by automated diffractometer methods. The lattice constants from the experimental work are refined by least-squares methods; reflections are assigned hkl indices consistent with space group extinctions. Relative intensities, calculated densities, literature references, and other relevant data are included.

Standard X-Ray Diffraction Powder Patterns of Fifteen Ceramic Phases

Fifteen reference patterns of oxide ceramics are reported. Included in the fifteen reference patterns are data for nine high critical temperature superconducting oxide and related phases Ba 2 Cu 3 ErO 7 , Ba 3.2 Cu 1.7 Er 0.8 O 6.1 ·xCO 2 , Ba 2 Cu 3 HoO 7 , Ba 2 Cu 3 (Pr 0.5 Y 0.5 )O 7 , Ba 3 Dy 4 O 9 , Ba 3 Yb 4 O 9 , (Ba 0.6 Sr 0.4 ) 2 Cu 3 YO 7 , (Ba 0.8 Sr 0.2 ) 2 Cu 3 YO 7 , and CuNd 2 O 4 . The general methods of producing diese X-ray powder diffraction reference patterns were described previously in this journal (Vol. 1, No. 1, pg. 40 (1986)). The symbols used in diis article are defined in the PDF cards.

Observations of Dislocations in Ammonium Dihydrogen Phosphate: Production of Dislocation‐Free Crystals

The results of etch‐pit and diffraction topographic studies on ammonium dihydrogen phosphate (ADP) are reported. These studies were carried out on specimens sectioned by abrasive wheel and string‐saw from large single crystals grown from aqueous solution. The two characterization methods are shown to be in approximate one‐to‐one correspondence in the case of sections produced by abrasive sawing. Absence of both etch pits and topographic images in sections made by string‐sawing of material well removed from the seed region is taken to indicate that this material is dislocation‐free. Preliminary results on the plasticity of ADP are reported.

Reference X-Ray Diffraction Powder Patterns of Fifteen Ceramic Phases

Fifteen reference patterns of boride, silicide, selenide, telluride and oxide ceramics are reported. Included in the 15 reference patterns are data for three oxide phases which are related to high critical temperature (T c ) superconducting materials: BaCuO 2 , BaCuSm 2 O 5 and BaCuYb 2 O 5 . Four other patterns are included which represent phases previously not contained in the PDF. The remaining six are major corrections of data already included in the file. Reference data for phases Ba 2 CuY 3 O 6.8 and Ba 2 Y 3 CuO 6 appeared in the special July superconductor issue of the Advanced Ceramic Materials , 1987. The general methods of producing these X-ray powder diffraction reference patterns are described in this journal, Vol. 1(1), 40 (1986). Samples were mixed with one or two internal standards: silicon (SRM640a), silver, tungsten, or fluorophlogopite (SRM675). Expected 2θ values for these internal standards are specified in the methods described ( ibid. ). Data were measured with a computer controlled diffractometer. The POWDER-PATTERN system of computer programs was used to locate peak positions, to calibrate the patterns, and 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.