The production of low-loss, tunable composite ceramic materials with
improved breakdown strengths is disclosed. The composite materials
comprise ferroelectric perovskites such as barium strontium titanate or
other ferroelectric perovskites combined with other phases such as
low-loss silicate materials and/or other low-loss oxides. The composite
materials are produced in sheet or tape form by methods such as tape
casting. The composite tapes exhibit favorable tunability, low loss and
tailorable dielectric properties, and can be used in various microwave
devices.