Low‐Temperature Sintering of β‐Spodumene Ceramics Using Li₂O–GeO₂ as a Sintering Additive

Abstract

Low-temperature sintering of b-spodumene ceramics with low coefficient of thermal expansion (CTE) was attained using Li 2 O-GeO 2 sintering additive. Single-phase b-spodumene ceramics could be synthesized by heat treatment at 1000°C using highly pure and fine amorphous silica, a-alumina, and lithium carbonate powders mixture via the solid-state reaction route. The mixture was calcined at 950°C, finely pulverized, compacted, and finally sintered with or without the sintering additive at 800°C-1400°C for 2 h. The relative density reached 98% for the sample sintered with 3 mass% Li 2 O-GeO 2 additive at 1000°C. Its Young's modulus was 167 GPa and flexural strength was 115 MPa. Its CTE (from R.T. to 800°C) was 0.7 3 10 À6 K À1 and dielectric constant was 6.8 with loss tangent of 0.9% at 5 MHz. These properties were excellent or comparative compared with those previously reported for the samples sintered at around 1300°C-1400°C via melt-quenching routes. As a result, b-spodumene ceramics with single phase and sufficient properties were obtained at about 300°C lower sintering temperature by adding Li 2 O-GeO 2 sintering additive via the conventional solid-state reaction route. These results suggest that b-spodumene ceramics sintered with Li 2 O-GeO 2 sintering additive has a potential use as LTCC for multichip modules.I. Reimanis-contributing editor Manuscript No. 32743.

Preparation of Li2CO3 Nanoparticles by Carbonation Reaction Using a Microfiltration Membrane Dispersion Microreactor

“…Li 2 CO 3 powder can be used as long-term lithium therapy for acute mania, 3−5 raw materials for lithium conductor synthesis, 6−12 and additives for low melt-point ceramics or glass manufacture. 13 Decreasing the size of Li 2 CO 3 powder has benefits in delivering drugs promptly 14 or producing materials in a more efficient or controllable way. In fact, the material synthesis processes using Li 2 CO 3 always include a timeconsuming ball-milling step to pulverize powders for providing a uniform reactants mixture.…”

Microstructural investigation of thermo-mechanically processed lithium slag for geopolymer precursor using various characterization techniques

“…Similar trends of agglomeration were observed in the case of two hours of calcination. Pre-calcination post grinding produced a higher particle size than that of an inverse case due to the sintering of particles [46]. Moreover, the particle agglomeration is compliant with that of trends of atomic crystallite sizes which endorses the crystal transformation in lithium slag during processing.…”

“…Thus, the aggregation of crystals not only depends on the grinding energy but also the abrasion resistance of a particular mineral. Moreover, the calcination of lithium slag before grinding induced resistance to abrasion of Spodumene phase as the crystallite size of Spodumene is higher than that of pre-grinding and post-calcination phase might be due to some level sintering of Spodumene during calcination phase [46]. The agglomeration of crystals is prominent when raw lithium slag was calcined without prior or post-grinding, as a result the Spodumene, Anorthite, Quartz, and Gypsum experience enlargement of crystallite size due to the sintering effect.…”

Chemical Preparation Routes and Lowering the Sintering Temperature of Ceramics

“…The difference in the coefficient of thermal expansion comes from the possibility of counterbalancing the inevitable expansion of the M-X bonds with the temperature by rotation of certain bricks of the structure (XO 4 tetrahedron, BO 6 octahedron, etc.). The resulting expansion of the unit cell, and thus all the ceramic, macroscopically, is limited or even suppressed (NASICON-like or cordierite structures) [195][196][197][198][199] or even a contraction can take place (spodumene-and eucrytite-like structures) anisotropically [180,[200][201][202][203][204][205][206][207][208][209].…”