Hollandites’ crystal chemistry, properties, and processing: a review

Abstract

This review provides a broad overview of the structural characteristics, compositional flexibility, and structure-property relationships of hollandite materials. Hollandites have a general formula A x B 8 O 16 , x ≤ 2, with 'A' cations located in one-dimensional tunnels formed by a framework of 'B'-O octahedra. With numerous possibilities for chemical and structural modifications, hollandite family provides many opportunities to manipulate its properties for specific applications. First, we review the chemistry, structure-property relationship, and processing techniques for various applications. The primary focus is on the cumulative effects of Aand B-cation interaction, and the resultant parameters including unit cell symmetry, cation order-disorder, electronic and/or magnetic coupling, that dictate the material's applicability. Then, selected applications, such as crystalline hosts for radioactive caesium disposal, electrode material for Li-ion batteries, and ferromagnetic materials, are outlined from a structure-property relationship perspective. Finally, processing strategies in correlation with structural evolution and applications are briefly addressed.

Significantly Enhanced Balance of Dielectric Properties of Polyvinylidene Difluoride Three-Phase Composites by Silver Deposited on K2Ni0.93Ti7.07O16 Hollandite Nanoparticles

“…In recent years, potassium titanates K x Ti 8-y Me y O 16 with the hollandite structure have been of particular interest due to the possibility of their modification and a wide range of applications, including electrode materials for energy storage devices, gas sensors, catalysts, etc. [56][57][58][59][60]. In addition, recent publications report that hollandite-like solid solution ceramics can exhibit high dielectric constants (ε ′ = 10 3 -10 4 ) [61,62], which also makes them attractive materials as ceramic fillers for high dielectric polymer composites.…”

Permittivity and Dielectric Loss Balance of PVDF/K1.6Fe1.6Ti6.4O16/MWCNT Three-Phase Composites

“…In addition to traditional ceramic ferroelectrics, the hollandite-like potassium titanates with K x (Me,Ti) 8 O 16 can be used as functional fillers [ 25 , 26 ]. In recent years, it has been noted that ceramics based on potassium titanates can exhibit a permittivity comparable to well-known high-K materials [ 27 , 28 ].…”

Dielectric properties of PMMA/KCTO(H) composites for electronics components

“…These materials can be synthesized by solid state reaction, sol-gel technology and hydrothermal method. 15 In this research copper-containing hollandite has been produced according to the technology based on the modification of the amorphous potassium polytitanate powder (PPT) in the aqueous solution of copper sulfate, followed by the thermal treatment and sintering. Hollandite-like solid states of various compositions were synthesized using this technology.…”

“…The perspective ceramic fillers for polymer‐matrix composites are the hollandite‐like solid solutions due to their stable and high value of permittivity. These materials can be synthesized by solid state reaction, sol–gel technology and hydrothermal method 15 . In this research copper‐containing hollandite has been produced according to the technology based on the modification of the amorphous potassium polytitanate powder (PPT) in the aqueous solution of copper sulfate, followed by the thermal treatment and sintering.…”