A comparison of syntheses approaches towards functional polycrystalline silicate ceramics

TL;DR

This paper compares three synthesis methods for polycrystalline silicate ceramics, highlighting their effects on phase formation, densification, and microstructure, with practical guidelines for designing functional silicate ceramics.

Contribution

It provides a comparative analysis of co-precipitation, sol-gel, and solid-state methods for silicate ceramics, emphasizing process control and phase formation.

Findings

Co-precipitation enhances sintering and densification.

Modified sol-gel method achieves better phase control.

Zn2+ substitution promotes orthoenstatite formation.

Abstract

This study aims to shed light on processing pathways towards functional silicate ceramics, which show some promise in various emerging applications, including dielectrics and bioactive implant materials. Polycrystalline silicate ceramics of Neso, Soro and Inosilicate families were synthesised by three different techniques: (i) a co-precipitation method, (ii) a modified sol-gel method and (iii) standard solid-state reactions. Co-precipitated samples show increased sintering and densification behaviour compared to sol-gel and solid-state methods, with diametral shrinkage values during sintering of 28.8%, 13.3% and 25.0%, respectively. Well-controlled phase formation in these ceramics was most readily achieved through the steric entrapment of cations and shorter diffusion pathways afforded by the modified Pechini-type sol-gel method. Substituting Zn2+ for Mg2+ in enstatite samples was found to enhance the formation of orthoenstatite during cooling, which is otherwise very slow. We present guidelines for the design of synthesis methods that consider the requirements for different functional silicate ceramics in terms of phase formation and microstructure.