Some Compounds of Tungsten-Bronze Type A6B10O30 (B=Nb, Ti or Nb, W)

Effects of substituting Ti or W for Nb in A6B10O30-type niobates are examined. The general formula of the sample studied here is described as Anp+A6-nq+Bmr+Nb10-m5+O30, where Br+=Ti4+ or W6+ and A1+=K, Na, A2+=Ba, Sr, A3+=Bi, La. There are found several tungsten-bronze type compounds. In order to elucidate the effect of Ti or W substitutions, they are classified on the basis of ionic radii and the value of n (or m), and the tungsten-bronze field is roughly determined. Variations with composition of lattice parameters and dielectric peak temperatures are considered based on the present classification.