Browsing by Author "FUN, HK"

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STRUCTURE OF THE NEW TLBA2PRCU2O7-X BY RIETVELD ANALYSIS
(1993-12-01)
LEE, TJ
;
FUN, HK
;
WANG, A
;
CHOU, CH
;
LAI, CC
The crystalline structure of new TlBa2PrCu2O7-y was obtained at room temperature from X-ray powder diffraction with CuKalpha radiation using Rietveld analysis. TlBa2PrCu2O7-x is semiconducting at room temperature with a TlBa2CaCu2O7 type (1212) structure (space group P4/mmm) and cell parameters a = 3.91836(3) angstrom, c = 12.5498(2) angstrom. The structure was refined for 15 parameters to R(wp) = 6.89 %, R(p) = 5.09 % for 6323 step intensities and R(b) = 13.24 % for 138 reflections.
STRUCTURES AND ANTIFERROMAGNETIC PR ORDERING MECHANISM OF TL(BA2-XSRX)PRCU2O7-Y COMPOUNDS BY RIETVELD ANALYSIS
(1994-04-10)
FUN, HK
;
YANG, P
;
LAI, CC
;
KU, HC
;
LEE, TJ
The crystalline structures of Tl(Ba2-xSrx)PrCu2O7-x (x=0, 0.4, 0.8, 1.0, 1.2, 1.6, 2) were obtained at room temperature (300 K) and low temperature (100 K) from X-ray powder diffraction with Cu Kalpha radiation using Rietveld analysis. Tl(Ba2-xSrx)PrCu2O7-x has an isotypical structure with TlBa2CaCu2O7(1212) at 300 and 100 K, i.e., the tetragonal system, space group P4/mmm, Z=1. The relationships between the Pr-O(1) bond lengths and the O(1)-Pr-O(1) bond angles with the antiferromagnetic ordering temperature T(n) (Neel temperature) are discussed. The mechanism of the decrease in the antiferromagnetic ordering temperature T(n) as well as the nonsuperconductivity of this system are explained using the Pr(4f) and O(2p) orbital hybridization and the Pr-O(1) bond lengths. The suggested mechanism of Pr-Pr coupling (interplanar Pr-Pr distance) for the Pr ordering by a previous study is inconsistent with our experimental results.