Investigation of barium strontium titanate thick films for tunable phase shifters

The influence of the microstructure of Ba0.6Sr0.4TiO3 (BST) bulk ceramics a nd thick films on the dielectric properties have been studied. Thick films have been prepared by screen printing technique on Al2O3 substrates. The po wder has been prepared by using the common mixed oxide technique. In compar ison to dense bulk ceramics, the permittivity of thick films is approximate ly 10 times less. The effect of temperature on the permittivity and the tun ability (change of the dielectric constant with applied voltage) has also b een investigated at low frequency (1 kHz). At microwave frequencies, BST th ick films have been characterized by measuring coplanar waveguides (CPW) at room temperature and utilizing an enhanced quasi-static CPW model for mult ilayer dielectric substrates. (C) 2001 Elsevier Science Ltd. All rights res erved.