Cold Sintering: A Paradigm Shift for Processing and Integration of Ceramics

Abstract

This paper describes a sintering technique for ceramics and ceramic-based composites, using water as a transient solvent to effect densification (i.e. sintering) at temperatures between room temperature and 200 °C. To emphasize the incredible reduction in sintering temperature relative to conventional thermal sintering this new approach is named the "Cold Sintering Process" (CSP). Basically CSP uses a transient aqueous environment to effect densification by a mediated dissolution-precipitation process. CSP of NaCl, alkali molybdates and V2 O5 with small concentrations of water are described in detail, but the process is extended and demonstrated for a diverse range of chemistries (oxides, carbonates, bromides, fluorides, chlorides and phosphates), multiple crystal structures, and multimaterial applications. Furthermore, the properties of selected CSP samples are demonstrated to be essentially equivalent as samples made by conventional thermal sintering.

Cold Sintering Process: A Novel Technique for Low‐Temperature Ceramic Processing of Ferroelectrics

“…The terminology of Cold Sintering is actually adopted from powder metallurgy, in which highly dense compacts can be obtained by a Cold Sintering process whereby the metal nanoparticles are consolidated at room temperature or ultralow temperatures (generally <400°C) via plastic flow that is driven by extremely high pressures, in a magnitude of GPa range. 33,34 The materials that have been successfully cold sintered cover broad chemical variations and crystal structures, ranging from binary through quinary compounds that include oxides, fluorides, chlorides, iodides, carbonates, and phosphates. The proposed Cold Sintering Process in our work is actually a low-temperature liquid phase sintering process assisted by easily approachable pressures in the MPa magnitude.…”

Geologically-inspired strong bulk ceramics made with water at room temperature

“…Recent work on cold sintering processes applied to ceramics910 has demonstrated impressive densification of various inorganic materials at mild temperatures under hydrothermal conditions. Typically, temperatures in the range 120–180 °C have been utilized to promote densification of oxides through cold sintering.…”

Ceramic–Salt Composite Electrolytes from Cold Sintering

“…Cold sintering of ceramic electrolytes requires the application of a small amount of solvent, high pressure, and modest temperatures to leverage a dissolution-precipitation process that reduces sintering temperatures to less than 200 °C; [20] nevertheless, this process can lead to amorphous grain boundaries that are detrimental to ionic conduction. [18,23] We thus propose that the addition of a second phase, such as a Li salt, can reduce grain boundary resistances.…”

“…[9,12,[14][15][16][17] Such a sintering process has obvious limitations, including Li loss, impurity phase formation, incompatibility with organic materials, difficulties in integrating all-solid-state batteries with composite cathodes, and high processing cost. [18,[20][21][22][23] As a consequence, ceramics such as alkali molybdates, BaTiO 3 , and Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) can be sintered at a temperature that is an order of magnitude lower than through conventional means. [18,[20][21][22][23] As a consequence, ceramics such as alkali molybdates, BaTiO 3 , and Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) can be sintered at a temperature that is an order of magnitude lower than through conventional means.…”

“…[18,19] A recently developed approach, cold sintering, can densify ceramics near 100 °C by incorporating a transient solvent phase and uniaxial pressure into the process. [18,[20][21][22][23] As a consequence, ceramics such as alkali molybdates, BaTiO 3 , and Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) can be sintered at a temperature that is an order of magnitude lower than through conventional means. [18,23] Furthermore, the low processing temperature of cold sintering enables co-sintering of ceramics with polymers, for applications in microwave dielectrics (Li 2 MoO 4 / polytetrafluoroethylene), semiconductors (V 2 O 4 /poly(3,4ethylenedioxythiophene)-poly(styrenesulfonate), and solid electrolytes (LAGP/poly(vinylidene fluoride-co-hexafluoropropylene)).…”