Synthesis, crystal structure and thermal behavior of Rb3B7O12, a new compound

R. S. Bubnova, I. G. Polyakova, S. V. Krivovichev, I. P. Shakhverdova, S. K. Filatov, M. G. Krzhizhanovskaya, P. C. Burns

Результат исследований: Научные публикации в периодических изданияхстатья

19 Цитирования (Scopus)

Аннотация

A new compound, Rb3B7O12, has been synthesized using solid state reaction and glass crystallization methods. It is triclinic, space group P-1, a = 6.603(1), b = 6.632(1), c= 30.085(6), Å, α = 91.183(4), β = 91.781(4), γ = 119.293(3)°, V = 1147.5(5) Å3, Z =4. The crystal structure of the compound has been solved by direct methods and refined to R1 = 0.068 (ωR = 0. 142) on the basis of 1840 unique observed reflections (|Fo| > 4σ |Fo|). The structure is based upon a novel [B7O12] layered anion. The layer is parallel to (0 0 1) and is composed of four types of rigid boron-oxygen groups: two [B5O8.5]2- pentaborate groups, [B3O5]- triborate groups and BO4 single tetrahedra. There are six symmetrically independent Rb atoms in the structure, of which four are located in voids within the borate layer and two are between the layers. High-temperature X-ray powder diffraction studies showed that the new compound forms above 620 °C as a result of the solid state reaction Rb2B4O7 + α-RbB3O5 ↔ Rb3B7O12. The compound melts at ∼ 700°C according to the peritectic reaction Rb3B7O12 ↔ βRbB3O5 + liquid. Thermal expansion of the structure of Rb3B7O12 is highly anisotropic (α11 = 34, α22 = 9, α33 = 2 × 10-6°C-1). The thermal expansion is maximal in the direction perpendicular to the plane of the layer (α11 = 34 × 10-6°C-1).

Язык оригиналаанглийский
Страницы (с-по)985-992
Число страниц8
ЖурналSolid State Sciences
Том4
Номер выпуска7
DOI
СостояниеОпубликовано - 1 янв 2002

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