Experimental planning of the synthesis of strontium molybdate by EDTA-citrate and its structural influence, morphology and optical bandgap

It was initially used a 23 experimental design with central point in triplicate to synthesize strontium molybdate by EDTA-citrate combined complexation method, where the influence of pH (6, 7.5 e 9), calcining time (3, 4 e 5 h) and heating rate (5, 7 e 10 °C min−1) was investigated. Single-phase powders were obtained when calcined at 650 °C with tetragonal crystalline structure. The heating rate is the most influent independent variable on the intensities of the X-ray diffractions peaks. The synthesized powders are shown as agglomerates with irregular spherical and bipyramidal morphology. According to the experimental design, the conditions of calcining time of 3 h and heating rate of 10 °C min−1 show the lowest values of energy band gap (4.18 and 4.17 eV) for pH 6 and 9, respectively. The statistical models generated were able to describe the phenomena observed.