AN INVESTIGATION OF MICROPOROUS CETINEITE-TYPE PHASES A(6)[B12O18][CX3](2)[D-X(H2O,OH,O)(6-Y)] - I - THE CETINEITE STRUCTURE FIELD

Hydrothermal syntheses between 120 and 200 degrees C have been perform ed to determine the chemical variability of semiconducting microporous materials with cetineite structure. The syntheses were based on the g eneral formula A(6)[B12O18][CX3](2)[D-x(H2O,OH,O)(6-y)], (0 less than or equal to x less than or equal to 2; 0 less than or equal to y less than or equal to 6), which was derived from X-ray crystal structure re finements. A = Li+, Na+, K+, Rb+, Cs+, Tl+, NH4+, Ca2+, Sr2+, and Ba2 were introduced as hydroxides, in some cases as carbonates, B = C = A s3+, Sb3+, and Bi3+, and X = S2-, Se2-, and Te2- as elements. Only syn theses with B = C = Sb3+ and X = S2- and Se2- were successful. Known c etineite-type phases now include the element combinations A/Sb3+/S2- w ith A = Na+ and K+, and A/Sb3+/Se2- with A = Na+, K+, Rb+, Sr2+, Ba2+, and probably Tl+. Variable amounts of Na+, Sb3+ and C4+ were found to occupy the D position of the cetineite-type structure. The chemical v ariability can be described by the coupled substitutions A(+)+H2O<->A( 2+)+OH-, mH(2)O<->Dm++mOH(-), and nOH(-)<->Dn++nO(2-). The crystals ob tained are orange to dark red, in agreement with their semiconducting properties.