Bi(1-x/3)1 circle divide (x/3) (V1-xMOx)O-4 (x from 0 to 0.75 in steps of 0.15), Bi(1-x/3)+y circle divide ((x/3)-y) (V1-xMox-yFey)O-4 (x = 0.45; 0.00 less than or equal to y less than or equal to 0.15 in steps of 0.05), Bi1-x/3 circle divide Fe-(x/3)-y(y) (V1-xMox-yFey)O-4 (x = 0.45; 0.00 less than or equal to y less than or equal to 0.15 in steps of 0.05), Bi(1 -x/3)circle divide Ce-(x/3)-y(y) (V1-xMOx-y- Fe-y)O-4 (x = 0.45 and 0.60; 0.00 less than or equal to y less than or equal to x/3, in steps of 0.05), and Ce(1-x/3)circle divide (x/3) (V1-xMOx)O-4 (x from 0 to 0.60 in steps of 0.15) solid solution systems (circle divide = cation vacancy in the eight-coordinated sites, tetrahedrally coordinated cations in parenthesis) have been prepared by coprecipitation and final firing at 873 K. Structural characterization has been performed by lattice parameter measurements. Optical and magnetic properties have also been investigated. The X-ray analysis showed that the great majority of materials are monophasic with tetragonal scheelite-type structure. The correlation between unit cell volume and metal composition shows the effect of the cation and vacancy substitution on the unit cell lattice, which is interpreted in terms of the different ionic radii of the interchanging metal ions and of filling up or creation of cation vacancies.