Development of a β-LiAlSi2O6:Cr-based Ceramic Pigment by Proteic Sol-Gel Process Using Gelatin: Synthesis and Characterization

Ricardo Ferrari Ferraz,Jaine Ferreira Sousa,Daniel Dos Santos Costa,Héstia Raissa Batista Reis Lima,Raquel Aline Pessoa Oliveira

doi:10.1590/1980-5373-mr-2021-0315

Abstract

A novel pigment of β-LiAlSi2O6:Cr ceramic was developed by a partial proteic sol-gel process, using gelatin as a ligand. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and visible and near-infrared diffuse reflectance spectroscopy (vis-NIR DRS) were performed. XRD results confirmed that the crystal structure of the lattice corresponded to β-LiAlSi2O6 (or β‑spodumene), and the addition Cr3+ ions by doping did not interfere in the formation of this crystalline phase. EDS confirmed the homogeneous existence of Cr3+ dopant in β‑LiAlSi2O6 particles. From the vis‑NIR DRS, selective absorption of visible light wavelengths was identified in the bands of 425 nm and 600 nm, resulting in the perception of a yellowish-green color when β-LiAlSi2O6 is doped with Cr3+. CIE-XYZ colorimetric coordinates were generated to characterize the resulting colors. The obtained results demonstrated the viability of β‑LiAlSi2O6:Cr synthesis by a proteic sol‑gel route and its great potential for obtaining a yellowish-green ceramic pigment.

Highlights

Ceramic pigments can assign color from the dispersion of insoluble particles
This paper reports the development of β-LiAlSi2O6, which corresponds to the synthetic polymorph of spodumene with a tetragonal structure, doped with Cr3+ ions and synthesized by a proteic sol-gel route using gelatin as a ligand, aiming at the production of a novel ceramic pigment
The X-ray diffraction (XRD) patterns were compared with the standard reference ICSD 26817, being verified that the used sample corresponds to β-LiAlSi2O6, which belongs to the tetragonal crystal system having the space group P43212

Summary

Introduction

Ceramic pigments can assign color from the dispersion of insoluble particles. The selective absorption of visible light wavelengths occurs due to the action of a chromophore ion (usually transition metals) incorporated in the structure of the lattice[1]. The sol-gel route represents a valuable technique for obtaining materials, in which the organic and inorganic members are closely linked[22,23], and shows a few advantages, including the ability to produce a solid-phase material from a chemically homogeneous precursor[24] This method is used in several applications, mainly due to the good homogeneity and low sintering temperatures[10]. The heating rates for the drying and calcining processes must be slow enough to prevent material retraction during solvent elimination and organic cross-linked polymeric chains degradation In this context, this paper reports the development of β-LiAlSi2O6, which corresponds to the synthetic polymorph of spodumene with a tetragonal structure, doped with Cr3+ ions and synthesized by a proteic sol-gel route using gelatin as a ligand, aiming at the production of a novel ceramic pigment. The processes of synthesis and characterization of the crystalline structure and optical behavior are discussed

Experimental

Results and Discussions

Conclusions