A comparison of the clinopyroxene compounds CaZnSi₂O₆and CaZnGe₂O₆

Abstract

Single crystals of CaZnSi2O6 (calcium zinc silicate) and CaZnGe2O6 (calcium zinc germanate) were synthesized at 1623 K and 2.5 GPa by slow cooling of the melts from 1473 K. Structure solution using Patterson methods revealed the two compounds to be isomorphous and thus isostructural. They adopt the clinopyroxene structure type with space group C2/c. The substitution of Ge4+ for Si4+ increases the distortion of the tetrahedra and octahedra. The increased size of the tetrahedral GeO4 chain is mainly compensated by (i) increasing the kinking of the tetrahedral chain and (ii) lengthening the Zn-O bonds.

Usage of P–V–L bond theory in studying the structural/property regulation of microwave dielectric ceramics: a review

“…Clinopyroxene-type ABC 2 O 6 (A = Ca; B = Co, Mg, Zn, Fe; CvSi, Ge) materials are crystallized as a monoclinic structure with a C2/c space group. [96][97][98] Huber found out that the petedunnite CaZnSi 2 O 6 phase stabilizes at P > 0.8 GPa; otherwise, it decomposes into Zn 2 SiO 4 , Ca 2 ZnSi 2 O 7 and SiO 2 if the pressure is low and temperature exceeds 650 °C. 99 Distortions of the polyhedra were quantitatively analysed by Heuer in a CaBSi 2 O 6 system (B = Fe, Zn).…”

Ca3ZnGeO2[Ge4O12]: a Ca–Zn germanate related to the mineral taikanite

“…Apex atom O5 of the Ge2 site shares corners with two Ca2 and one Ca1 site, interconnecting the slab of tetrahedral sites with the sheet of ZnO 6 and CaO 8 polyhedra. The average Ge-O distances are 1.777 (7) and 1.754 (7) Å for Ge1 and Ge2, respectively, which are values typically found in germanate compounds with chain structures (Redhammer & Roth, 2005). In taikanite and CMS-XI, the tetrahedral sites are distinctly more regular when compared to those in the title compound.…”

“…This tetrahedron also displays higher polyhedral distortion, with a tetrahedral quadratic elongation (TQE) of 1.0352 and a large tetrahedral bond-angle variance (TAV) of 162.7 2 . The tetrahedron around the Ge2 site is somewhat more regular, with TQE = 1.0160 and TAV = 73.62 2 , but is still far away from the values of a regular GeO 4 tetrahedron, such as found in Ge-pyroxenes with 'zweier' single chains; in CaZnGe 2 O 6 , a TQE value of 1.0111 and a TAV value of 47.44 2 were reported by Redhammer & Roth (2005). While the Ge1 tetrahedron shares only corners with neighbouring polyhedra, two edges of the base plane of the Ge2 tetrahedron are common with two neighbouring Ca2O 8 polyhedra, and the third edge is common to the neighbouring Ca1O 8 polyhedron.…”

“…The corresponding distortion parameters in taikanite for the Mn 3+ O 6 octahedron are OQE = 1.0248 and OAV = 36.74 2 . For comparison, the regular ZnO 6 octahedron in the pyroxene-type compound CaZnGe 2 O 6 has OQE = 1.0106 and OAV = 34.22 2 , with bond lengths ranging from 2.096 (3) to 2.176 (3) Å (Redhammer & Roth, 2005). The Mn1 site of taikanite, which represents a compressed Mn 3+ O 6 octahedron, with four medium and two short distances between 1.88 and 2.15 Å , is occupied by Ge 4+ (Ge3) in the title compound.…”

A dynamic irradiation-responsive material for advanced anti-counterfeiting in dark and bright fields

“…15) and a band gap of 4.2 eV. 23,24 As shown in Fig. 1b and Table S2, (ESI †) it contains three cation sites including dodecahedral CaO 8 , octahedral ZnO 6 , and tetrahedral GeO 4 sites.…”