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How can low-melting glasses reduce the firing temperature of ceramic capacitors?

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Figure 1: Ferroelectric properties of barium titanate (BaTiO3). (Left) Above 120° C the structure of the BaTiO3 crystal is cubic, and there is no net polarization of charge; (right) below 120° C the structure changes to tetragonal, shifting the relative positions of the ions and causing a concentration of positive and negative charges toward opposite ends of the crystal. — capacitor dielectric and piezoelectric ceramics Figure 1: Ferroelectric properties of barium titanate (BaTiO₃). (Left) Above 120° C the structure of the BaTiO₃ crystal is cubic, and there is no net polarization of charge; (right) below 120° C the structure changes to tetragonal, shifting the relative positions of the ions and causing a concentration of positive and negative charges toward opposite ends of the crystal.

Low-melting glasses act as fluxing agents that facilitate the sintering process in multilayer capacitors. By introducing these additives, the sintering temperature of the ceramic can be reduced to approximately 1,100° C (2,000° F).1

This reduction is essential for the manufacturing of these components, as it allows the ceramic dielectric layers to be cofired with electrode alloys that have lower melting points. Furthermore, the use of these additives enables the development of ceramic compositions that can be cofired with less expensive metals, such as nickel or copper, instead of costly precious metals like palladium and silver. The liquid phase created by these additives promotes densification through mechanisms such as viscous flow and solution-precipitation, which help bond the particles together at lower temperatures than would be required for solid-state sintering.123