New Pyrochlore Pb 2 II [In 0.5 Sb 1.5 ]O 6.5

From the study of the hypothetical series Pb   2 II [Pb   2+2p–2c IV In c–2p Sb c ]O 6+p (O ⪕ p < 1; 0 ⪕ c < 2), the existence of the cubic pyrochlore Pb 2 II [In 0.5 Sb 1.5 ]O 6.5 has been established. This compound was obtained as an orange yellow powder, S.G. Fd 4 m (No. 227), Z = 8, a = 10.5892(1) Å, V = 1187.38(3) Å 3 , D c = 8.48 M gm −3 . For Pb in 16(c) positions, In and Sb (1:3) randomly distributed in 16(d), oxygen atoms in 48(f) and in a half of the 8(a) sites, and oxygen positional parameter x = 0.429 (origin at center, 3 m), R = 0.062. The apparent interatomic distances (Å) are determined: PbO = 2.612; (In, Sb)O = 2.019.