Figure 3. Pseudocell dimensions (based on Z = 2) of the polymorphs of Bi₂O₃ versus temperature.

Cell dimensions have been reduced to correspond to Z=2Bi₂O₃, in the following arbitrary manner: pseudo-orthorhombic—monoclinic polymorph

a′(Z=2) = (½)a(Z=8), b′(Z=2) = (½)b(Z=8), c(Z=2) =c(Z=8). Cubic—cubic polymorph

a(Z=2)=a(Z=2).

Tet—tetragonal polymorph

a′(Z=2) = (½)a(Z=8), c(Z=2)=c(Z=8).

b.c.c.—body-centered cubic polymorph

$a^{\prime }\left(Z=2\right)=\sqrt[3]{2/13}$ (Z=13).

α=coefficient of linear thermal expansion, calculated by method of least squares on original data.

●—from certified reagent grade (ACS) Bi₂O₃.

△—from “Spec. pure” grade Bi₂O₃.