LA1-XBAXCR1-YTIYO3 WITH VARIED OXYGEN-CONTENT

Formation of the La(1-x)Ba(x)Cr(1-y)Ti(y)O(similar to 3)is investigate d in the range of 0.0 < x < 0.2 and 0.0 < y < 0.5, with x less than or equal to y. Redox behavior and electrical conductivity are studied as functions of partial pressure of oxygen. In pure oxygen atmosphere at 1000 degrees C, the miscibility limits are x(m) = 0.05(2) (when x < y ) and y(m) < 0.19(1) (when x = 0) accompanied by demixing of BaCrO4 an d La2Ti2O7, respectively. The y(m) value is increased to at least 0.5 under p(o2) = 10(-23) atm, where a large portion of Ti-IV is reduced t o Ti-III. Electrical conductivity is governed by the redox behavior of Cr and Ti, with a minimum close to the stoichiometric point with Cr-I II and Ti-IV present. A relatively high n-conductivity appears when Ti (donor) is in excess of Ba (acceptor), but the effect of Ba is still seen in the oxidized region where Ba promotes oxidation of Cr-III. The rmodynamic data are evaluated for the reduced region, and are in quali tative agreement with the chemically analyzed oxidation state of Ti.