Short-range order to long-range order transition in rare-earth metal oxide thin crystals

1977 ◽  
Vol 33 (6) ◽  
pp. 992-996 ◽  
Author(s):  
V. K. Kaul ◽  
U. Saxena
Keyword(s):  
Rare Earth ◽  
Metal Oxide ◽  
Long Range ◽  
Rare Earth Metal ◽  
Short Range ◽  
Short Range Order ◽  
Earth Metal ◽  
Range Order ◽  
Long Range Order ◽  
Rare Earth Metal Oxide

Pb()O3-type Perovskites: Part I. Pair-correlation Theory of Order-disorder Phase Transition

1997 ◽  
Vol 12 (8) ◽  
pp. 2117-2126 ◽  
Author(s):  
Hyun M. Jang ◽  
Su-Chan Kim
Keyword(s):  
Long Range ◽  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order ◽  
Statistical Thermodynamic ◽  
Range Order Parameter ◽  
Long Range Order ◽  
Short Range Order Parameter

The limitation of the long-range order parameter and the necessity of the short-range order parameter for the thermodynamic description of Pb()O3-type perovskites are discussed. Based on the discussion, a statistical thermodynamic model that takes into account the configuration of the neighboring B-site ions (B′ and B″ cations) was developed. A pair-correlation approximation was used in the calculation of the configurational entropy and the long-range coulombic interaction energy between the nearest B-site ions. The theoretical calculations using Pb(Sc1/2Ta1/2)O3 (PST) and Pb(Sc1/2Nb1/2)O3 (PSN) systems indicate that the short-range order parameter persists over a wide range of temperatures examined (0–1800 K) and that there possibly occur consecutive long-range order-disorder transitions in the configuration of B-site cations. The possibility of the existence of short-range ordering above the long-range order-disorder transition temperature was also examined using the annealed PSN specimen as a typical example of Pb()O3-type perovskites.

On `non-stoichiometric phases' in thin films of rare-earth oxides

1978 ◽  
Vol 34 (6) ◽  
pp. 1025-1027 ◽  
Author(s):  
M. Gasgnier ◽  
P. Caro
Keyword(s):  
Thin Films ◽  
Rare Earth ◽  
Long Range ◽  
Short Range ◽  
Short Range Order ◽  
Rare Earth Oxides ◽  
Range Order ◽  
Acta Cryst ◽  
The Rare Earth

Kaul & Saxena [Acta Cryst. (1977), A33, 992-996] have reported the existence of long-range and short-range order in a non-stoichiometric phase 'LnO x ' (Ln = rare earth). It is shown that the experiments they are describing are indeed the oxidation of the rare-earth hydride LnH2 into the rare-earth cubic C-type sesquioxide. The interpretation they give of their experiments is to be discarded entirely.

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