Large-area BaxSr1-xTiO3 (BSTO-x) thin films, partially Fe-doped, have been grown by pulsed laser deposition (PLD) on technically relevant polycrystalline alumina based ceramics. The capacity (dielectric constant 8,) and Q-factor of planar Pt/BTO:Fe/Pt capacitors were investigated within a temperature range from -35 to +85 degreesC. The applied DC-bias voltages were up to 10 V and the measurement frequency was 1 kHz. Although operating in the ferroelectric state below the Curie temperature, pure BaTiO3 (BTO) thin films showed the smallest variation of E, within the temperature range from -35 to +85 degreesC compared to BSTO-0.6 and BSTO-0.8. The temperature dependence of E, below the Curie temperature (ferroelectric state) seems to be smaller than above the Curie temperature (paraelectric state) for the BSTO-x system. A homogeneous tunability of the capacity of about 60% was achieved for applied electrical DC voltages resulting in electrical field strengths between 0 and 5 V/mum within the whole temperature range. The Q-factor of 2 mum thick BTO films increases with increasing DC bias voltage. Furthermore, by Fe-doping of BTO films Q-factors could be increased by a factor of three up to about 70 compared to the not doped films. In addition, the temperature dependence of capacity is considerably influenced by Fe-doping. At a microwave frequency of 30 GHz high epsilon(r) values of about 1500 were measured for large-area BSTO-0.45 films at room temperature deposited directly on microwave ceramic substrates. Low values of tan delta of about 0.003 were measured for the PLD-BSTO-0.45 films which corresponds to a Q-factor of more than 300. The results show the potential of ferroelectric BTO thin films for applications as tunable electronic devices in a wide temperature range. (C) 2003 Elsevier Ltd. All rights reserved.