Synthesis and Unusual Properties of Tetragonal Pb‐Containing Oxymolybdates Based on La₂MoO₆

Abstract

Polycrystalline (PbO) x (La 2 MoO 6 ) (1-x)/2 (x = 0, 0.05, 0.1, 0.2, 0.34, 0.4) samples have been prepared by solid-state reactions near 900°C. Phase-pure compounds with the layered tetragonal La 2 MoO 6 structure have been obtained in the range 0 ≤ х ≤ 0.34. Pb doping of La 2 MoO 6 has been shown to cause [a] M.

Fluorite‐like LixLn5–xMo3O16.5–1.5xFx (Ln = La, Pr, Nd) compounds isostructural with Nd5Mo3O16

“…They were shown to exhibit a piezoelectric response at room temperature and undergo a reversible first‐order ferroelectric phase transition near 600°C, where their conductivity rises sharply. Such behavior was observed previously for Pb‐doped Ln 2 MoO 6 oxymolybdates 26,27 . They have a layered tetragonal structure made up of MoO 4 tetrahedra and LnO 8 cubes, as in the case of Ln 5 Mo 3 O 16 28,29 …”

Effect of Sodium and Fluorine Co‐Doping on the Properties of Fluorite‐Like Rare‐Earth Molybdates of Nd5Mo3O16 Type

“…The appearance of the above features in the properties of NaLn 4 Mo 3 O 15 F compounds may be due to very insignificant structural changes since their diffractograms do not differ from that of the pure Nd 5 Mo 3 O 16 . It should be noted that the appearance of ferroelectric‐superionic phase transition was also observed in lead doped oxymolybdates Ln 2 MoO 6 (Ln = La, Nd) with a layered tetragonal structure having a fluorite‐like Ln2O2 layer and close in composition to Ln 5 Mo 3 O 16 molybdates …”

Synthesis, structure and properties of layered Pr2MoO6-based oxymolybdates doped with Mg

“…They were found to be made up of fluorite layers, each containing two sheets of NdO 8 or LaO 8 polyhedra, with a sheet of isolated MoO 4 tetrahedra sandwiched between them. Analysis of X-ray diffraction data for (PbO) x (Nd 2 MoO 6 ) (1-x)/2 and (PbO) x (La 2 MoO 6 ) (1-x)/2 samples, doped with divalent Pb (Voronkova et al, 2016(Voronkova et al, , 2017, indicated that the layered tetragonal phase had an extended stability region. Near 1073 K, an antiferroelectric phase transition was identified, due to the transformation of the I4 1 /acd phase into an I " 4 42m phase on cooling.…”

“…However, doping of the oxymolybdates, e.g. with Pb, was found to cause drastic changes in their conductivity and other properties, as mentioned above (Voronkova et al, 2016(Voronkova et al, , 2017. Among other bivalent impurities doping Nd 2 MoO 6 , the structure with magnesium is known (Voronkova et al, 2019).…”