ON THE EXISTENCE OF PRSRO3-TYPE PHASE AND ITS BI PR-SUBSTITUTED SOLID-SOLUTION/

Solid solution of the Pr-1.1(1-x)Bi0.8xSr0.9+0.3xO2.932+0.049x-type ha s been obtained and characterized through X-ray diffraction, effective valency of Pi and Pr, and through the density measurements. At 900 de grees C in air this solid solution begins from the Pr1.1Sr0.9O2.932-te rminus and extends toward Bi2Sr3O6 up to x congruent to 0.5 (20 at % B i). Its crystal structure represents monoclinically distorted perovski te-type atomic arrangement, identical to that occurring in the Tb1-xBi xSrO3 analog, several Tb-, and/or Pr-alkaline-earth binaries of the RE (+4)MeO(3)-type (Me = Sr or Ba), and to a large group of RE(+3)Bi(+5)S r(2)O(6)-type ternaries. Characteristic features of this solid solutio n are (i) independent on x, constant oxidation states of Pr and Bi, eq ual to +3.694 and +4.565, respectively, resulting in x-dependent incre ase of the average effective valency of these components ((V) over bar ); (ii) x-dependent deficiency of the overall oxygen index, decreasing to 0 far above the solubility limit of Bi; and (iii) x-dependent defi ciency of the cationic sublattice, increasing with the factor proporti onal to 0.2x/(0.9 + 0.3x), i.e. to the atomic fraction of total Sr ion s located on Pr sites. (C) 1996 Academic Press, Inc.