Dielectric properties of ceramic composite with nanosized Ni on tubular halloysite template under high frequency

Halloysite is an inexpensive nanoclay mineral with a tubular structure. A ceramic composite with nano-sized Ni on the halloysite template is fabricated by electroless deposition, and its dielectric properties at an applied frequency of 2-18 GHz, are primarily investigated at different post-annealing temperatures and contents. Results indicate that the permittivity and dielectric loss values increase with the increase of composite contents, while decrease with the post-annealing temperature. The post-annealing treatment at different temperatures causes a transformation of nano-sized metallic Ni from an amorphous to crystal structure, which significantly affects the dielectric properties of the composite, especially in its percolation state. The resonant peaks of the composite shift toward high frequency at elevated annealing temperature. Due to its desirable advantages under high frequency, such as low weight, tunable permittivity and dielectric loss, the composite can be used for new dielectric ceramic materials.