Cold sintered CaTiO3-K2MoO4 microwave dielectric ceramics for integrated microstrip patch antennas

Abstract

This is a repository copy of Cold sintered CaTiO3-K2MoO4 microwave dielectric ceramics for integrated microstrip patch antennas.

Cold sintered LiMgPO4 based composites for low temperature co‐fired ceramic (LTCC) applications

“…To confirm further the coexistence of three phases in composites, Raman spectra of cold‐sintered LMP‐CTO‐KMO samples are shown in Figure 2F. As reported previously, 36, 10, and 39 Raman bands are commonly observed in LMP, CTO, and KMO respectively 25,50,51 . For LMP, there are 18 external modes (<400 cm −1 , 12 translations of Li, Ni, PO 4 tetrahedra, six vibrations of PO 4 tetrahedra), and 18 internal modes of PO 4 tetrahedra (>400 cm −1 , P‐O stretching: ν 1 = 974 cm −1 , ν 3 = 1020‐1080 cm −1 , O‐P‐O bending and P vibration: ν 2 = 416‐468 cm −1 , ν 4 = 590‐650 cm −1 ), Figure .…”

“…Moreover, LMP has a large negative TCF (–55 ppm/°C) that falls outside excepted values for LTCC and ULTCC (+/–30 ppm/°C) applications. To adjust TCF closer to zero and to improve density, a bespoke cold sintering flux, 0.8KMO‐0.2CTO (TCF = +70 ppm/°C) was developed based on KMO (TCF = –70 ppm/ o C) but with a large positive TCF, adjusted through adding CTO (+850 ppm/ o C) 25 . Forming composites in this manner is typically used in commercial LTCC which are composed of a low melting temperature glass matrix with negative TCF and high ε r , positive TCF phases such as TiO 2 49 …”

“…The geometric method was used to calculate the bulk density ( ρ ) of samples, as reported elsewhere 25,26 …”

“…Raman spectra were obtained using a Renishaw inVia Raman spectroscopy. The measurement of MW properties ( ε r , TCF, tan δ and Q × f ) was conducted by the TE 01δ mode with a vector network analyser (Advantest R3767CH), following previously defined protocols 25,26 . The cavity was heated by a Peltier device and the resonant frequency ( f ) was measured from 25°C to 85°C.…”

“…Cold sintering is a radical departure in sintering technology in comparison with LTCC and ULTCC and employs an aqueous phase and uniaxial pressure to densify ceramics at <300°C for shorter times (<2 hours) than conventional sintering 25−43 . The energy consumed by cold sintering is <50% of that used by its conventional counterpart, 6 facilitating integration with polymers and base metals and liberating RF design space for ceramics, previously forbidden by their high sintering temperatures.…”