TUNGSTEN AND NIOBIUM-TUNGSTEN INTERGROWTH BRONZES (ITB) PREPARED BY CHEMICAL-TRANSPORT REACTIONS

Intergrowth tungsten bronzes A(x)WO(3), A=K, Rb and Cs, x<0.1, have be en prepared by chemical transport using HgCl2 as a transporting agent. Crystals of up to 8 mm size were obtained which were found by electro n diffraction and high-resolution electron microscopy to be, in most c ases, rather well-ordered (1,n) ITB. The samples always contained crys tals representing different members of the structure family (different n values), however. A weak correlation between composition (x) and st ructure (n) was found. ITB phases A(x)Nb(y)W(1-y)O(3), with y<x have a lso been prepared being intermediate between the fully reduced bronze (y=0) and the fully oxidized bronzoid (y=x). This offers the possibili ty of varying the electronic properties continuously while the structu re is preserved.