STUDIES OF PHASE RELATIONS IN THE Cs2O-V2O5-V2O3 SYSTEM AT LIQUIDUS TEMPERATURES AND 10 - 25 less than PO(2) less than 10 - 10 ATM. PREPARATION OF SOME MIXED-VALENCES Cs-V OXIDE CRYSTALS BY MELT GROWTH.

Single crystals (some mm in size) of four mixed-valence Cs-V oxides; Cs//yV//3O//7 (y equals 0. 3-0. 4), Cs//yV//2O//5 (y equals 0. 3), Cs//2V//5O//1//3 and CsV//2O//5, have been grown from fused CsVO//3 plus V//2O//5 mixtures in a mini-furnace under strict control of oxygen partial pressure and continuous visual inspection. The growth conditions were roughly: 10** minus **2**0 less than p//0//(//2//) less than 10** minus **1**5 atm (10** minus **1**5-10**1**0 Pa), 500 less than T less than 700 degree C and 0. 1 less than Cs/V less than 1. A study of phase relations at liquidus temperatures and controlled p//O//(//2//) in the range 10** minus **2**5-10** minus **1**0 atm was also undertaken with the mini-furnace. Based on the observations of phase transition temperatures between different Cs-vanadates(V), vanadium (IV,V) oxides and Cs-V(IV,V) oxides, the appearance of a part of the liquidus surface including tentative phase field boundaries is sketched.