Efficient Use of a Polyamine Carboxylate Ligand to Probe the Extent of Incorporation of Stereochemically Active Bi³⁺ in ThO₂

Abstract

Realizing the advantages of atomic level mixing, high homogeneity precise stoichiometric control and low processing temperatures, co‐precipitation route employing the polyamine carboxylate, ethylenediamine tetra acetic acid (EDTA) has been followed to determine the extent of dissolution of bismuth in ThO2 adopting fluorite structure. While the precursors containing varying amounts of Th4+ and Bi3+ were X‐ray amorphous, calcining them at 800 °C for 6 h yielded crystalline oxides with fluorite structure till Th0.40Bi0.60O2‐δ. This was supported by Raman spectral measurements in which defect band due to oxygen vacancies was present at around 590 cm−1 in addition to the band due to fluorite at around 460 cm−1. An increasing trend of cubic lattice constant with progressive substitution of bismuth in ThO2 was observed. The direct band gap was found to decrease with increase in bismuth content and was lying in the range of 2.54‐3.62 eV. Porous morphology of the samples was evident in their scanning electron microscopic images and they were macro porous as determined from surface area analysis measurements. Th0.50Bi0.50O2‐δ was found to efficiently catalyze the reduction of some nitroaromatics for nearly six cycles.

Metastable Bi2Zr2O7 with Pyrochlore-like Structure: Stabilization, Oxygen Ion Conductivity, and Catalytic Properties

“…The observed splitting of band in the vicinity of 1100 cm −1 could be attributed to metal−nitrogen coordination. 21,24,25 The out-of-plane bending of the carboxylate anion appeared in the range of 930−850 cm −1 . Bands in the region of 595−495 cm −1 were attributed primarily to M−O stretching modes, of which the band at 595 cm −1 signified Zr− O stretching mode, and Bi−O stretching mode manifested at 473 cm −1 .…”

“…17−20 Our recent success in establishing the limit of dissolution of bismuth in fluorite-structured thoria kindled our curiosity to address some of the issues related to the stabilization of pyrochlore-like Bi 2 Zr 2 O 7 by employing a chelate-based wet-chemical bottom-up synthesis and to further investigate their oxygen ion conductivity and catalytic property. 21,22 2. EXPERIMENTAL SECTION 2.1.…”

“…Both Bi 2 Hf 2 O 7 and Bi 2 Zr 2 O 7 phases have been found to be metastable. Bi 2 Zr 2 O 7 having defect fluorite structure has been synthesized by co-precipitation, hydrothermal, and solution combustion methods with a singular objective of using them as photocatalysts. − Our recent success in establishing the limit of dissolution of bismuth in fluorite-structured thoria kindled our curiosity to address some of the issues related to the stabilization of pyrochlore-like Bi 2 Zr 2 O 7 by employing a chelate-based wet-chemical bottom-up synthesis and to further investigate their oxygen ion conductivity and catalytic property. , …”

Luminescence properties of Eu3+‐ and Tb3+‐doped δ‐Bi2O3 stabilized by Th4+ substitution

“…Inspired from such co‐doping approach, it was planned to stabilize δ ‐Bi 2 O 3 firstly by substituting with Th 4+ , followed by doping it with spectroscopically rich trivalent lanthanides such as europium and terbium to further study their luminescent characteristics. The choice of Th 4+ for the stabilization of δ ‐Bi 2 O 3 was guided from our earlier studies . Additionally, luminescent property evaluations on Eu‐ and Tb‐doped fluorite structured thoria systems are available readily to assess our results in order to reach crucial conclusions .…”

“…The choice of Th 4+ for the stabilization of δ-Bi 2 O 3 was guided from our earlier studies. [28][29][30] Additionally, luminescent property evaluations on Eu-and Tb-doped fluorite structured thoria systems are available readily to assess our results in order to reach crucial conclusions. [31][32][33][34] The matching ionic radius of Th 4+ (1.04 Å) with the dopants of current study, low phonon energy of thoria matrix and the existence of only disordered defect fluorite structure with bismuth were other legitimate reasons behind our choice for the current study.…”