Dielectric Properties of Lithium Molybdate Ceramic Fabricated at Room Temperature

Abstract

Lithium molybdate disks were fabricated by moistening watersoluble Li 2 MoO 4 powder with deionized water and compressing it under a pressure of 130 MPa. Disks were postprocessed at room temperature, at 120°C, and at 540°C, which is a common sintering temperature for Li 2 MoO 4 . Regardless of the postprocessing temperature, densities as high as 87%-93% of the theoretical value were achieved. The X-ray diffraction patterns of processed disks were all the same with no signs of hydrates or constitutional water. The samples also exhibited very similar microstructures and microwave dielectric properties with a relative permittivity of 4.6-5.2 and a Q 3 f value of 10 200-18 500 at 9.6 GHz, depending on the postprocessing temperature.

3D printed dielectric ceramic without a sintering stage

“…The driving force of the consolidation of the Li 2 MoO 4 in the RTF method is pressure 21 which in the case of extrusion depends on the paste rheology, the extrusion rate, and the dimensions and the geometry of the dispenser 31 . Immediately after deposition of the paste, consolidation continues with the aid of the liquid phase and related capillary forces.…”

“…For microwave devices, Li 2 MoO 4 is of interest because of its beneficially low dielectric loss in addition to its low sintering temperature of 540 °C 19,20 . However, Li 2 MoO 4 is water-soluble, enabling component manufacture at temperatures as low as room temperature 21–24 . In this method, referred to as room temperature fabrication (RTF), Li 2 MoO 4 powder is moistened with water.…”

“…Thus, no shrinkage is observed. The dissolved Li 2 MoO 4 recrystallizes during drying due to water evaporation, which can be speeded up by heat treatment at 120 °C 21 . The RTF method has also been applied in the manufacture of Li 2 MoO 4 based composites to tailor the relative permittivity 22,23 and its thermal coefficient 23 , or to introduce magnetic properties 25 .…”

Novel water insoluble (NaxAg2−x)MoO4(0 ≤ x ≤ 2) microwave dielectric ceramics with spinel structure sintered at 410 degrees

“…In ULTCC, microwave dielectric ceramics can be densified without sintering aids since they are fabricated from intrinsically low melting point oxides. [10][11][12][13][14] [19] reported that dense ceramics can be obtained by …”

Room‐temperature‐densified Li2MoO4 ceramic patch antenna and the effect of humidity

“…One of these materials is microwave dielectric lithium molybdate (Li 2 MoO 4 ) which is conventionally densified by sintering at 540°C and which exhibits a relative permittivity (ε r ) of 5.5 and a dielectric loss value (tan δ) of 0.00028 at 13.051 GHz . To decrease fabrication temperatures even further, a novel method for room‐temperature densification of Li 2 MoO 4 has recently been presented, based on the water solubility of Li 2 MoO 4 . Densification of the Li 2 MoO 4 ceramic takes place at ambient temperature during sample pressing and is followed by a postprocessing step at 120°C to remove the residual water from the sample.…”