The ceramic composites containing 1-25 vol% BaTiO3 in a ferrite matrix phase of Ni0.3Zn0.7Fe2O4 were fabricated by sintering at 1250°C in air. The sintered composites indicated a steep increase in dielectric permittivity in a small BaTiO3 ratio up to 5 vol%. In a limited BaTiO3 ratio of 3-15 vol%, a reaction between Ni0.3Zn0.7Fe2O4 and BaTiO3 resulted in the production of a liquid phase during sintering, which caused correspondingly the formation of secondary phases of BaFe2O4 ss and hexagonal BaTiO3 ss. These solid phase and microstructure changes, however, brought about little contribution to the increasing permittivity of the composites. Electrical property evaluations combined with compositional analysis revealed that the remarkably increasing permittivity could be predominantly attributed to the electron hopping between Fe 2+ and Fe 3+ in the ferrite matrix, which was caused by the incorporation of a small amount of Ti 4+ into the spinel sublattice.

NiCuZn ferrite(Ba 0.7 Sr 0.3 )TiO 3 (BST) composite ceramics with the BST content of up to 50 vol % were fabricated by sintering compacted powder mixtures at 900°C. The granulation of the BST powder and addition of a Bi 2 O 3 -based oxide additive effectively assisted the densification of the composite samples. The samples thus fabricated showed required ¾ r values whereas their ® r values were considerably reduced, especially for those with lower BST contents. From the detailed examinations on the effect of the Bi 2 O 3 -based oxide additives and on the process modification to improve the reduced ® r values, the addition of a Bi 2 O 3 ZnO additive with the eutectic composition of as low as 1 wt % was enough to produce a densified 10 vol % BST composite sample with a highest ® r value. It was also found that the incorporation of ferrite granules calcined at 600°C caused further improvement of ® r . Thus, a densified 10BST composite sample with ® r = 125 was fabricated by low-temperature sintering at 900°C.

Here, the nanostructure of TiO2 photocatalytic films was controlled for photocatalytic applications using glancing angle sputter deposition and oxygen-ion–assisted reactive evaporation (OARE). The grain size and surface asperity both increase as the deposition angle increases, and films with high porosity were obtained at high incidence angles. However, the film deposited using sputtering has a much larger column diameter and a denser structure than the film deposited using OARE. Therefore, the film deposited using glancing angle sputter deposition at an incidence angle of 80° had much better photocatalytic properties than the film deposited using OARE: it was superhydrophilic after 1 h of UV irradiation and showed excellent organic decomposition performance. An increase in the porosity of this film led to a significant increase in its UV absorptance, which also improved its photocatalytic performance. In particular, the film deposited at 80° using sputtering had a UV absorptance above 70%.

Ceramic composites were fabricated from powder mixtures of BaTiO 3 and Ni 0.3 Zn 0.7 Fe x O 4± with different Fe contents of x = 1.8, 1.9, 2.0, 2.1, and 2.2 to examine the effect of the Fe content on the dielectric permittivity (r) of the composite samples. The r values of the composites were greatly affected by the Fe content such that a small r value of the Fe1.8 composite sample steeply increased with an increasing Fe content by about three orders of magnitude for the Fe2.1 and Fe2.2 samples. The strong Fe content dependence could be correlated with the incorporation of the Ti 4+ ions into the octahedral sublattices in the ferrite structure. The Ti-substitution would preferentially contribute to charge compensation for the Fe-poor ferrites, whereas it should result in the creation of the Fe 2+ ions on the octahedral sublattices of the Fe-rich ferrite phases.Therefore, the presence of the Fe 2+ ions synergetically created by the Ti-substitution and Fe-rich composition would be responsible for the considerably increasing r values for the Fe2.1 and Fe2.2 composite samples.

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