ABO₄ type scheelite phases in (Ca/Sr)MoO₄ - BiVO₄ - Bi₂Mo₃O₁₂ systems: synthesis, structure and optical properties

Abstract

The cation deficient complex oxides of (Ca/Sr)MoO4 - BiVO4 - Bi2Mo3O12 triple system are promising photocatalysts and pigments. Compounds with general formula of Ca1−1.5x-yBix+yФxMo1-yVyO4 and Sr1−1.5x-yBix+yФxMo1-yVyO4 were synthesized byconvention solid state technique in the range of 550–720 °C. Two wide regions of the solid solutions (ordinary and superstructured scheelite-type phases respectively) were found for each system. The diffuse scatering of homogeneous samples was investigated in the range of 190–1100 nm. Energy gaps calculated with linear approximation of Kubelka-Munk function decreases with bismuth and vanadium content.

Comparative characteristic of Bi- and La- doped (Ca/Sr)MoO4 -based materials with a defect scheelite-type structure

“…XPRD patterns of x ≥0.2 compositions contain reflections of (Ca/Sr)MoO4 and La2Mo3O12 phases. In the Sr1−3xBi2xФxMoO4 system (0≤ x ≤ 0.125), the patterns were indexed using a tetragonal scheelite model, while the patterns for the (0.125≤ x ≤ 0.225) compositions were indexed using a superstructured scheelite model (asup= √5asub, csup= csub), as in the previous studies [17,18].…”

“…In the substituted samples, this band slightly shifts to a higher wavelength (Figure 6). In general, the spectra are similar to those of (Ca/Sr)1−3xBi2xФxMoO4 [18]. Band gap (Eg) calculations were performed using the Kublenka-Munk theory and the Tauc relation [24].…”

“…Vibrational spectroscopy results revealed large distortions of MoO4 and BiO8 polyhedra [11] with a strong correlation between the A site substitution and the microwave dielectric properties. In later works, additional peaks identified by Guo et al in the compositions of Ca1−3xBi2xФxMoO4 above x = 0.15 could be indexed in the tetragonal supercell with asup ≈ √5a, csup ≈ c (where a and c are the tetragonal scheelite cell parameters) [16][17][18]. This superstructure was evident throughout the compositional range 0.15 < x ≤ 0.225 and was caused by bismuth ions ordering.…”

“…Compositions of the general formula (Ca/Sr)1-3xLa2xФxMoO4 and Sr1-3xBi2xФxMoO4, (0.025  x  0.275) series were synthesized by a conventional solid state method [18] from SrCO3 (99.0%, Reakhim), Bi2O3 (99.9%, Merck), La2O3 (99.9%, Merck) and MoO3 (99.5%, Reakhim) in the range of 600-900 °C and 500-700 °C respectively. The density of the homogeneous powders (ρexp) was determined using 2 ml pycnometers with distilled water as the displacement liquid.…”

Solid state pelletizing for the synthesis of new Bi-doped strontium molybdate and its development as a photocatalytic precursor for Rhodamine B degradation

“…On the other hand, also is showed as the effects on Eg, oxygen vacancies and reactive oxygen species can be explored thorough of a degradation methodology. For Rhodamine B was used this degradation method considering substation stoichiometric for with bismuth(III) and parameters such as time, concentration and exposition light [ [3] , [4] , [5] , [6] , [7] , [8] , [9] , [10] , [11] , [12] , [1] , [2] , [13] ].…”