Temperature‐dependent electrical transport behavior and structural evolution in hollandite‐type titanium‐based oxide

Abstract

Electrical transport behavior and structural characteristics directly determine the use of functional ceramic materials in electronic information storage, catalytic conversion, and energy field applications. However, these properties are poorly understood because most of the relevant experiments were performed in a rather narrow temperature range. Herein, we used hollandite‐type KxTi8O16 as an example to systematically study the temperature‐dependent structure and electrical transport properties in a wide temperature range from 25 to 900°C. The electrical transport involves both potassium ionic conduction and electronic conduction. With increasing temperature, the ionic conductivity increases below 800°C and decreases above 800°C. The electronic conductivity displays two maxima at 0.15 S/cm at 400°C and 5.2 × 10−4 S/cm at 800°C. These interesting variations in the conductivities are related to the presence of Ti3+ and the structural transformation from hollandite to a mixture of rutile and jeppeite. The findings reported herein support the potential application of titanium‐based hollandites and provide an understanding of the electrical transport properties of functional ceramic materials.

AC Conductivity and Dielectric Properties of Lepidocrocite-type Alkali Titanate Tunable by Interlayer Cation and Intralayer Metal

“…While fitting of the data to the equivalent circuit at close to RT is generally poor due to sorbed water (and are omitted from Table S1 and Figure S5), that does not affect σ which is directly obtained from the intercept. Table compares our σ values vs those from the literature. ,,,,,,,− …”

Theoretical Study on the Mechanism of the Initial Ammonolysis Reactions of the Main Raw Materials for the Formation of SiBCN Ceramics

“…Due to steric hindrance, the energy barrier of the HMDZ reaction is higher, such as reactions 2 – 3 ‐ 2 and 3 – 3 ‐ 2 . The energy barriers of the addition reactions are relatively high, and some vinyl groups are retained in the precursor structures [8] . When the HCl molecule is released from the reaction, it forms an ammonium salt with another nitrogen‐containing compound, which is an exothermic process as shown:…”

“…The precursor conversion method is the most commonly used method in experiments due to its low synthesis temperature, controlled molecular structure and excellent moulding performance, from organosilicon‐based polymers as precursors to further pyrolysis to ceramic materials [7] . In most common precursor conversion method, target single‐source precursors produced from small molecular monomers containing Si, B, C, and N are prepared to generate polyborosilazane (PBSZ) precursors by cross‐linking polymerization [8,9] …”

“…The general structure of the SiBCN precursor is shown in Scheme 1, which consists mainly of Si−N and B−N backbones [8] . Therefore, the formation of Si−N and B−N bonds directly determines the morphology and properties of the precursors.…”

Theoretical Study on Ion Diffusion Mechanism in W-Doped K3SbS4 as Solid-State Electrolyte for K-Ion Batteries

“…This limitation restricts the number of possible structures for solid electrolytes containing K-ion. K-ion has difficulty diffusing through the quadrangular O 4 sites. , They may be able to diffuse through the hexagonal O 6 sites in compounds like K 2 Fe 4 O 7 or the octagonal O 8 sites in hollandite structures, which is not common in solid oxides. , For now, the development of potassium SSE is comparable to slower than that of lithium SSE or sodium SSE. Exploring high-conductivity potassium SSE is of crucial significance for its commercialization.…”