Low-temperature sintering of ZnTiO3 using CaV2O6 as a liquid-forming additive for LTCC applications

Abstract

CaV2O6 (CV) is investigated as a sintering aid for the low-temperature densification of ZnTiO3 (ZT). The incorporation of 5 vol% of CV drastically decreases the sintering temperature of ZT from 1175 to 825 °C and prevents its decomposition to Zn2TiO4 and TiO2. The densification temperature reaches as low as 690 °C when the concentration of CV approaches 30 vol%. The formation of a eutectic at 687 °C from unreacted V2O5 and TiO2 present in CV and ZT powder, respectively, and the lowering of the melting point of CV in the presence of ZT, as evidenced by DSC analysis, are responsible for the low-temperature densification by liquid phase sintering. The XRD analysis indicates no reaction between the ZT and CV phases in the composites. The SEM analysis shows the presence of CV in the boundaries of ZT grains and a decrease in average grain size from 5.9 to 1.24 μm when the CV concentration increases from zero to 30 vol%. The permittivity value decreases from 24.25 to 22.71, and the loss factor increases from 7.449 × 10−4 to 1.321 × 10−3 when the CV concentration in the composite increases from 5 to 30 vol%. The composite containing 5 vol% CV shows the highest Qu × f value of 9215, a temperature coefficient of the resonance frequency of −51 ppm/°C, a thermal expansion coefficient of 9.3 ppm/°C, and a thermal conductivity of 4.72 Wm−1K−1. The ZT-CV composites are compatible with silver at their sintering temperatures, showing their suitability for LTCC applications.