REFINEMENT OF MICROSTRUCTURAL PARAMETERS OF THE CRYSTAL STRUCTURE OF COMPOUND BA2MOO5
DOI:
https://doi.org/10.32782/tnv-tech.2023.2.7Keywords:
crystal structure, Rietveld method, compound Ba2MoO5Abstract
Barium molybdates have a wide range of applications: in nuclear power, photoluminescent devices, solid-state lasers, photocatalysts, and gas sensing. They are used in microwave and thermoelectric devices. Ba2MoO5 belongs to this group of compounds. Several methods for its production are known from the literature. Ba2MoO5 is obtained by reactions: BaMoO4+BaCO3→Ba2MoO5+CO2, BaMoO4+Ba3MoO6→2Ba2MoO5. This chemical can also be obtained from the reaction of BaMoO4 with Mo and BaO2. Ba2MoO5 and Mo, BaMoO4 were formed, which did not react. According to the state diagram of BaO-MoO3, it borders on Ba3Mo7O24 and BaMoO4 . It has a melting point of 12800 C in the eutectic and 1370 °C in the melt. The presence of Ba2MoO5 was determined by X-ray phase analysis using the database of powder diffractograms with the Brag-Brentano geometry, PDF-2. The spectrum of the compound is available in the card 025-0011. The synthesis of the compound whose diffraction spectrum is reported in card 025-0011, PDF-2 database (ICDD) for 2009 was the result of the reaction of BaCO3 and MoO3 , taken in a molar ratio of 2:1, placed in a gold crucible and heated to 900 °C and kept in air for 4 days. From the analysis of the literature, it follows that Ba2 MoO5 crystallizes in orthorhombic syngony, has the Pnma symmetry group, lattice periods a = 7.4097A°, b = 5.7603A°, c = 11.3906A° and belongs to the K2VO2F3 structure type. Using the above information on the crystal structure of the studied compound, the microstructural parameters were refined using the spectrum published in card 025-0011 of the PDF-2 (ICDD) database for 2009. The values of the lattice periods were refined: a=7.408471A° , b=5.734523A°, c=11.469570A°, spatial symmetry group Pnma. Microstructural parameters: Ba(1) 4c x/a=0.178307; y/b=0.250000; z/c=0.416387; position filling factor s.o.f.=1; Ba(2) 4c x/a=0.482515; y/b=0.250000; z/c=0.715824; s.o.f.=1; Mo(1) 4c x/a= 0.1585(9); y/b=0.250000; z/c= 0.0671(5); s.o.f.=1; O(1) 4a x/a= 0; y/b=0; z/c= 0; s.o.f.=1; O(2) 4c x/a=0.731075; y/b=0.250000; z/c=-0.001550; s.=1; O(3) 4c x/a=0.336331; y/b=0.250000; z/c=0.904934; s.o.f.=1; O(4) 8d x/a=0.267908; y/b=0.134197; z/c=0.053091; s.o.f.=1.
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