Effect of sintering temperature on the percolation threshold and the dielectric properties Ca[(Li 1/3Nb 2/3) 1–x Ti x]O 3–δ – Ag composite

Abstract

The Ca[(Li 1/3Nb 2/3) 1– x Ti x ]O 3– δ + Ag (CLNT + Ag) composites were prepared by solid state ceramic route and its dielectric properties were investigated as a function of silver loading. The sintering temperature of the CLNT ceramics was lowered to 950 °C/2 h by the use of (Li 2CO 3–B 2O 3–SiO 2) LBS glass additive. The effect of sintering temperature on the percolation threshold of ceramic–silver composites was investigated. The dielectric properties were systematically characterized in terms of relative permittivity, dielectric loss and conductivity with volume fraction of silver, frequency and temperature. The relative permittivity of the composite increases with silver content and it is in good agreement with power law below the percolation limit. Addition of 0.17 volume fraction of silver increases the relative permittivity of CLNT + 5 wt% LBS from 32 to 270 at 1 MHz. The maximum increase in relative permittivity ( ε r ≈ 4 × 10 5) with low dielectric loss (tan δ ≈ 10 –2) at 1 MHz was observed for 0.18 volume fraction of silver. The relative permittivity of the composites was found to be independent of temperature for all the range of silver loading investigated in this study. CLNT + 5 wt% LBS with 0.18 volume fraction of Ag shows the capacitance density of 0.265 μF/cm 2 and 21.5 μF/cm 2 at 1 MHz and 100 KHz, respectively. This offers the perspectives for application of this composite in decoupling and electromechanical devices.