Formulation and characterization of sinterless Barium Strontium Titanate (BST) nanocomposite dielectric inks for flexible RF and Microwave electronics applications

The demand for printable electronics over conventional electronics is rising exponentially due to various reasons. Tunable radio frequency (RF) and microwave (MW) devices make a high impact on the size, cost and the overall performance of flexible electronics. The dielectric constant of BST can be tailored by an applied electric field, which allows BST to be used in varactors for tunable RF and MW applications such as tunable filters and conformal antennas.

The Curie temperature (T_C) of (Ba_XSr_1-XTiO₃) can be tailored by adjusting the molar fraction of barium. BST has a paraelectric phase above the Curie temperature and below the Curie temperature, BST has a ferroelectric phase. BST shows highest dielectric properties such as tunability, high dielectric constant and low loss tangent in the paraelectric phase.

These inks can be processed below 150 ⁰C and a high performance can be achieved without sintering the BST nanoparticles. Also, these inks are compatible with different types of printing technologies, such as dispensing and ink jet and aerosol jet. These BST-polymer inks showed 44.29 ± 1.85 as the highest dielectric constant and 0.02 ± 0.01 as the lowest loss tangent at 10 GHz. The maximum tunability achieved was 15% at 10 GHz with an applied electric field of 10 V/µm.