Crystal Structure of Piezoelectric Bismuth Germanium Oxide Bi12GeO20

Abstract

Piezoelectric Bi12GeO20 crystallizes in the cubic system with space group I23 and lattice constant a = 10.1455±0.0008 Å at 298°K. The complete x-ray scattering pattern within a reciprocal lattice hemisphere of radius (sinθ)/λ = 1.02 Å−1 was determined with PEXRAD. A total of 4812 reflections were measured, resulting in 631 independent and significantly nonzero Fmeas. The crystal structure was solved using three-dimensional Patterson and Fourier series, and refined by the method of least squares. The final agreement factor R is 0.062. The germanium atoms occupy geometrically regular tetrahedra, with Ge–O=1.717±0.028 Å. The bismuth atoms are heptacoordinated: five oxygen atoms form an incomplete octahedral arrangement, with Bi–O distances ranging from 2.076±0.027 to 2.640±0.028 Å. The remaining two oxygen atoms are electrostatically coordinated, on either side of the 6s2 inert electron pair in Bi3+, at distances of 3.082 and 3.170 Å from bismuth. The Bi atom vibrates anisotropically. The absolute configuration of the atomic arrangement has been determined. The positive piezoelectric polarization induced by compressive stress applied along 〈111〉 is given by the normal to a triangular GeO4 tetrahedral face in the direction from the Ge atom to the face.

Atomic structure and crystal chemistry of sillenites: Bi12(Bi3+ 0.50Fe3+ 0.50)O19.50 and Bi12(Bi3+ 0.67Zn2+ 0.33)O19.33

“…3a). Admittedly (Abrahams et al, 1967;Craig & Stephenson, 1975), this Bi polyhedron is really an octahedron, the other position being occupied by its lone 6s 2 electron pair which is oriented in the direction opposite to the shortest Bi--O(l~) bond. Two Bi polyhedra sharing an O(lii)---O(l iii) edge form dimers (Fig.…”

“…• -3+ 3+ Bll2(Blo.50Feo.50)Olg.50 AND " .3+ 2+ All the previous investigations of sillenite single crystals since the initial study by Abrahams, Jamieson & Bernstein (1967) were carried out using X-ray analysis and were based on the oxygenstoichiometry approach (Craig & Stephenson, 1975;Efendiev, Kulieva, Lomonov, Chiragov, Grandolfo & Veccia, 1981;Swindells & Gonzalez, 1988). It is this approach that led Craig & Stephenson (1975), who studied the structure of sillenites with M= (Bi,Fe) and M= (Bi,Zn), to a structural-model concept in which the M-cation valence or effective valence of the isomorphous cationic mixture at the M site is always equal to four.…”

Absolute configuration and optical activity of laevorotatory Bi12TiO20

“…1 above. Bond distances for BGO are taken from the older structural data of Abrahams, Jamieson & Bernstein (1967) rather than the more recent data of . Devarajan & Glazer (1986)comment that these earlier results give a better fit in their calculation of optical rotatory power (see below).…”

Orientation and Temperature Dependence of Piezoelectric Properties for Sillenite-Type Bi12TiO20 and Bi12SiO20 Single Crystals

“…Sillenite-type Bi 12 MO 20 (where M = Ti, Si and Ge, known as BTO, BSO and BGO) crystals have non-centrosymmetric, body-centered cubic structure belonging to the I23 space group [1,2]. The structure of sillenite-type crystals was first determined by Sillen [3] and later refined by Efendiev and Wiehl [4,5].…”