Formation of the BiAl3(PO4)2(OH)6 Compound with a Waylandite Structure under Hydrothermal Conditions

• Published in: Russian journal of inorganic chemistry 2022, Vol.67 (6), p.850-860
• Main Authors: Elovikov, D. P., Tomkovich, M. V., Levin, A. A., Proskurina, O. V.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Density; Hydrothermal treatment; Infrared spectroscopy; Inorganic Chemistry; Mathematical analysis; Rietveld method; Synthesis and Properties of Inorganic Compounds; Unit cell; X ray powder diffraction; X-ray diffraction
• ISSN: 0036-0236; 1531-8613
• DOI: 10.1134/S0036023622060067

The BiAl 3 (PO 4 ) 2 (OH) 6 compound with a waylandite structure has been synthesized for the first time under hydrothermal conditions at 200°С and a pressure of 7 MPa. It has been shown that the compound forms through the formation of an intermediate crystalline phase—trigonal BiPO 4 —and an amorphous phase of composition 0.5[3Al 2 O 3 ⋅ 2P 2 O 5 ⋅ 6H 2 O]. According to SEM data, particles resembling in morphology particles of the phase with a waylandite structure are detected after 6 h of synthesis. The formation of BiAl 3 (PO 4 ) 2 (OH) 6 in amounts distinguishable by X-ray diffraction is fixed after 12 h and almost completely ends after 48 h of hydrothermal treatment of the suspension of precursors. The formation of waylandite is confirmed by SEM and IR spectroscopy. The structure of BiAl 3 (PO 4 ) 2 (OH) 6 was refined by the Rietveld method from powder X-ray diffraction data (space group (166) in hexagonal axes, unit cell parameters: a = 6.99608(5) Å, c = 16.1495(4) Å). Refinement gives the filling factors of unity within the standard deviation for the positions of atoms heavier than oxygen. The measured pycnometric density of the sample (4.01(8) g/cm 3 ) is slightly lower than the density calculated from the results of structure refinement (4.235(2) g/cm 3 ).