Alumina densification at low temperatures using CaV2O6 for LTCC application

Abstract

Low-temperature densification of alumina using calcium vanadate (CaV₂O₆, CV) having a similar dielectric constant as a liquid-forming additive has been studied. The alumina‒CV composites containing 20‒40 vol.% CV achieve ∼94% of theoretical density at low temperatures of 1100°C‒900°C by liquid-phase sintering. A reduction in the average size of grains from .87 to .42 µm with a surge in CV amount from 20 to 40 vol.% is observed. The permittivity decreases from 9.2 to 8.90, and the dielectric loss increases from 2.154 × 10^‒3 to 4.761 × 10^‒3 when the amount of CV in the alumina‒CV composite rises from 20 to 40 vol.%. The temperature coefficient of resonance frequency, thermal expansion coefficient, and thermal conductivity of the alumina‒CV composites are observed in the ranges of ‒54 to ‒72 ppm °C^‒1, 6.94‒7.32 ppm °C^‒1, and 13.78‒8.02 W m^‒1 K^‒1, respectively. The compatibility of the composites with Ag for low-temperature co-fired ceramics (LTCC) application is established through co-sintering and energy-Dispersive X-ray spectroscopy line spectra analysis. The low-temperature densification, acceptable range of dielectric and thermal properties, and silver compatibility make the alumina‒CV composite a candidate for LTCC application.