Nanocomposites and nanomaterials

Fabrication, structure and electrical properties of opal – KDP nanocomposites
Derhachov M.P., Pliaka S.M., Kushnerov O.I., Spichak O.O., Latyshova A.V.
Department of Physics, Electronics and Computer Systems, Oles Honchar Dnipro National University. Prospect Haharina, 72, Dnipro-49010, Ukraine. 
E-mail: derhachov_mp@dnu.dp.ua 

Nanocomposites with active dielectrics are efficiently applied in photonics and energy storage systems [1]. They may also serve as an excellent model structures to investigate the charge transfer under restricted volume conditions and in multi-grained nanoscale systems [2]. This work deals with fabricating opal–KH2PO4 (KDP) nanocomposite by employing the solution-based technique, and with investigating its structure and electrical properties within a 300 K – 573 K temperature range. 
KDP nanocrystals were grown in synthetic opal pores from water solution by reducing temperature from 323 K to 300 K. The samples with various grades of pores filling were obtained. Comparison between nuclei critical radius and pore size allows us to expect up to ten crystallites inside each pore. The X-ray powder diffraction patterns of the composites contain additional peaks, indicating an existence of additional crystalline phase together with usual tetragonal KDP phase. 
The temperature dependence of direct-current conductivity under the first time heating contains three regions with activation energies 0.17 eV, 0.41 eV, and 0.88 eV. At the next heating-cooling cycles one region with activation energy 0.88 eV is clearly detected. The value of static dielectric constant is estimated as 10. The frequency dependences of dielectric constant within the 100 Hz – 100 kHz region are discussed. 

1.	Armstrong E., O’Dwyer C. Artificial opal photonic crystals and inverse opal structures - fundamentals and applications from optics to energy storage // J. Mater. Chem. C.-2015.-3.- P. 6109-6143. 
2.	Lukin A. E., Ivanova E. N., Pan’kova S. V., Solovyev V.G., Veisman V. L. Electrical properties of silver iodide nanoparticles system embedded into opal porous matrix // J. Phys.: Conference Series.-2014.-572.-P. 012047(4).