New Bi₂Mo_1-xW_xO₆ Solid Solution:  Mechanosynthesis, Structural Study, and Ferroelectric Properties of the x = 0.75 Member

Abstract

To search for new ferroelectric materials exhibiting an Aurivillius structural type, the syntheses of the solid solution Bi 2 Mo 1-x W x O 6 has been undertaken. A phase with a large homogeneity range exists for 0.5 < x e 1.0. The thermal behavior of mechanochemically assisted precursor powders has been studied, showing that the consecutive crystallization of fluorite and Aurivillius-type phases arrives before a ferro-paraelectric transition occurs. TEM studies of the representative mechanoactivated 1:0.25:0.75 Bi 2 O 3 :MoO 3 :WO 3 mixture indicates that mechanosynthesis of a Bi 2 Mo 0.25 W 0.75 O 6 amorphous phase takes place. The ferroelectric properties of Bi 2 Mo 0.25 W 0.75 O 6 well-densified ceramic material have been measured. The crystal structure of Bi 2 Mo 0.25 W 0.75 O 6 has been refined using X-ray and neutron powder diffraction combined with Rietveld analysis. This oxide is isostructural with both γ(L) Bi 2 MoO 6 and Bi 2 WO 6 belonging to the orthorhombic system, space group Pca2 1 , a ) 5.44547( 7) Å, b ) 16.3731(2) Å, and c ) 5.46659(7) Å, V ) 487.40(1) Å 3 , Z ) 4, and F cal ) 9.21 g‚cm -3 . The structure keeps the Aurivillius-type framework with alternating [Bi 2 O 2 ] and [Mo/WO 4 ] layers. The structural characteristics of Bi 2 Mo 0.25 W 0.75 O 6 can be considered intermediate between those of γ(L) Bi 2 MoO 6 and Bi 2 WO 6 .

Glass formation and structure of glasses in the ZnO―Bi2O3―WO3―MoO3 system

“…Bi 2 WO 6 and Bi 2 MoO 6 are both end members of Bi 2 Mo 1 − x W x O 6 (0 ≤ x ≥ 1) solid solutions. In these structures the molybdenum and tungsten atoms are randomly distributed in the (Mo/WO 4 ) layers, surrounded by six oxygens in a quite distorted octahedral coordination[17]. A stronger distortion of the MoO 6 groups in Bi 2 MoO 6 compared to WO 6 in Bi 2 WO 6 was observed.…”

Synthesis of Nanovoid Bi2WO6 2D Ordered Arrays as Photoanodes for Photoelectrochemical Water Splitting

“…[4][5][6] Doping with N, C, and S or transition metals is commonly used to promote visible-light photocatalysis. [21][22][23][24][25][26][27][28] Recently, Bi 2 WO 6 has attracted extensive interest for its good performance in the photocatalytic degradation of organic compounds and the photocatalytic O 2 evolution, respectively, under visible-light irradiation. Therefore, there is an urgent need to develop efficient visible-lightactive photocatalysts.…”

Evidence of ferroelastic–ferroelastic phase transition in BiMoxW1−xO6 compounds

“…The existence of the of BiMo x W 1Ϫx O 6 solid solution has been established in the 0рxр0.50 8,9 range. Compositions with xϭ0, 0.1, and 0.25 were obtained in the form of ceramics, in one step thermal process, from mechanochemically activated amorphous powders 10 of the component oxides by sintering at 1173 K under a 300 kg/cm 2 axial pressure.…”

“…The remnant polarization and coercive field obtained from the loops, after correction of the non-switching charge, 9,13 are P r ϭ4 C/cm 2 and E c ϭ45 kV/cm, respectively. Low frequency, f ϭ0.1 Hz, ferroelectric hysteresis loops for sample BMW͑25͒ were traced with a virtual ground system.…”