Dielectric Tunability in Ferromagnetic-Ferroelectric Composite System

A new kind of lead-free ferromagnetic-ferroelectric (FM/FE) composite was successfully prepared by incorporating the dispersed 0.15Ni0.98Co0.02Fe2O4 (NCF) ferromagnetic nanoparticles into 0.85(K0.5Na0.5)NbO3-LiSbO3 (KNN-LS) ferroelectric micromatrix. The relative dielectric constant (εr) of the ceramic as a function of frequency (0.1 -200 kHz) under different dc bias electric field strengths was investigated in detail. εr increases with increasing dc bias electric field, while tanδ decreases with the increase in frequency. At room temperature, the high dielectric tunability (KD=11.41%) and high figure of merit (FOM=15.66) under the low dc electric field of 3 kV/cm, clearly imply that these ceramics are promising materials for tunable microwave device applications.

Electrophoretic Deposition Ba0.65Sr0.35TiO3 Thick Films for Tunable Microwave Devices

Pure barium strontium titanate (Ba0.65Sr0.35TiO3) and MnO2-modified barium strontium titanate (Ba0.65Sr0.35TiO3-MnO2) thick films were fabricated by electrophoretic deposition technique. The structures and morphologies of the films were analyzed. The dielectric measurements were conducted on metal-insulator-metal capacitors using platinum as the bottom electrodes and gold as the top electrodes. The dielectric constants and dissipation factors of Ba0.65Sr0.35TiO3 and Ba0.65Sr0.35TiO3-15wt% MnO2 thick films were measured at a frequency of 1 MHz. The tunabilities of 12.5% and 9.3% were obtained for Ba0.65Sr0.35TiO3 and Ba0.65Sr0.35TiO3-MnO2 thick films under an applied electric field of 15 kV/cm, respectively. The dielectric properties of the present thick films were suitable for tunable microwave device applications.