Synthesis and characterization of the barium oxalates BaC₂O₄·0.5H₂O, α-BaC₂O₄ and β-BaC₂O₄

Abstract

The synthesis of BaC(2)O(4).0.5H(2)O and its thermal decomposition to alpha-BaC(2)O(4) and beta-BaC(2)O(4) was investigated. BaC(2)O(4).0.5H(2)O is precipitated at room temperature from aqueous solutions of barium chloride and ammonium oxalate. The deuterated compound BaC(2)O(4).0.5D(2)O was made in analogy with D(2)O as the solvent. The compounds were characterized by X-ray and neutron diffraction analysis. Single-crystal X-ray diffraction of BaC(2)O(4).0.5H(2)O measured at 120 K gave the triclinic cell a = 8.692 (1), b = 9.216 (1), c = 6.146 (1) A, alpha = 95.094 (3), beta = 95.492 (3), gamma = 64.500 (3) degrees, space group P1, Z = 4. Two independent Ba atoms are each coordinated to nine O atoms at distances from 2.73 (1) to 2.99 (1) A. One of the two oxalate ions deviates significantly from planarity. The water molecule does form weak hydrogen bonds. In situ X-ray powder diffraction was used to study the thermal decomposition of BaC(2)O(4).0.5H(2)O and the formation of alpha-BaC(2)O(4). The X-ray powder pattern of alpha-BaC(2)O(4) measured at 473 K was indexed on a triclinic cell with a = 5.137 (3), b = 8.764 (6), c = 9.006 (4) A, alpha = 83.57 (4), beta = 98.68 (5), gamma = 99.53 (5) degrees, and the space group P1 with Z = 4.

Controlling the fluorescence and room-temperature phosphorescence behaviour of carbon nanodots with inorganic crystalline nanocomposites

“…For a given cation, exchange of the anions yields different crystal structures with different densities, e.g., SrC 2 O 4 ·H 2 O, SrCO 3 , and SrSO 4 have densities of 2.85, 3.78, and 3.95 g cm −3 , respectively. Sulphates (with the exception of gypsum), generally have higher densities for their respective cations (CaSO 4 ·2H 2 O, SrSO 4 , and BaSO 4 ρ = 2.32, 3.95, and 4.48 g cm −3 ), followed by carbonates (CaCO 3 , SrCO 3 , and BaCO 3 ρ = 2.71, 3.78, and 4.3 g cm −3 ) and finally oxalates (CaC 2 O 4 ·H 2 O, SrC 2 O 4 ·H 2 O, and BaC 2 O 4 ·0.5H 2 O ρ = 2.21, 2.85 45 , and 3.45 46 g cm −3 ). The relative RTP intensities follow this pattern, where they increase exponentially with density until a threshold (100%) relative RTP intensity is attained (Fig.…”

Anhydrous barium strontium oxalate

“…By varying the experimental conditions, different anhydrous metal oxalates M(C 2 O 4 ) can be obtained (M = Mn, Ni, Zn, Sn, Fe, Co or Cu; Kondrashev et al, 1985), resulting from thermal decomposition of the related hydrates (Naumov et al, 1996). The structures of -BaC 2 O 4 , -BaC 2 O 4 (Christensen et al, 2002), SrC 2 O 4 (Price et al, 1999), PbC 2 O 4 (Christensen et al, 1988) and CaC 2 O 4 (Deganello, 1981) have been determined by powder and single-crystal diffraction methods. In addition, the structures of La(…”