Synthesis, structural, morphological and optical properties of environment friendly yellow inorganic pigment Bi4Zr3O12

Abstract

This study reports on the structural, morphological, microstructural, electronic and optical properties of 5 nm (annealed at 300 °C) and 8 nm (annealed at 500 °C) sized nanocrystals of yellow inorganic pigment Bi4Zr3O12 prepared by sol-gel auto-combustion technique. Increase in the annealing temperature from 300 °C to 500 °C does not led to structural phase change but results in minor shifts in the 2θ position of Bragg peaks towards the higher angle side, which is attributed to reduction in the unit cell volume due to well crystallization. Phase pure formation and well crystallization of 8 nm sized Bi4Zr3O12 pigment in the fluorite type fcc symmetry in the space group Fm3‾m (No. 225) have been revealed first time by detailed Rietveld profile refinement of the X-ray diffractogram, FTIR, SAED and HRTEM analysis. The FESEM micrographs showed micro-flower type morphology of the rod shaped nanocrystals of the Bi4Zr3O12 pigments. EDS and XPS analysis confirmed the stoichiometry of the constituent elements present in the Bi4Zr3O12 pigments. XPS analysis evaluated +3, +4 and −2 oxidation states of the Bi, Zr and oxygen ions respectively and also rule out presence of organic species in the two pigments. ESR, Fluorescence and XPS analysis affirmed formation of oxygen vacancies in the two pigments. UV–Vis–NIR optical reflectance data showed marginal increment in the optical band gap upon raising the annealing temperature but 8 nm sized Bi4Zr3O12 nanocrystals have shown greater reflectance in comparison to 5 nm sized Bi4Zr3O12 nanocrystals. The photoluminescence spectroscopic analysis and CIE coordinates along with CCT values showed that yellow Bi4Zr3O12 pigment could be useful for optical devices and yellow pigment applications.