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Solid-State Materials for Batteries
Published in Elaine A. Moore, Lesley E. Smart, Solid State Chemistry, 2020
Elaine A. Moore, Lesley E. Smart
In 1968, Hagman and Kierkegaard found an exciting new material, sodium zirconium phosphate (NaZr2(PO4)3), known as NZP (Figure 6.14). The structure consists of corner-linked ZrO6 octahedra joined by PO4 tetrahedra, each of which cornershares to four of the octahedra. This creates a three-dimensional system of channels through the structure containing two types of vacant site: Type I, a single distorted octahedral site (occupied by Na+ ions in NZP), and three larger Type II sites (vacant in NZP). This has proved to be an incredibly versatile and stable structure with the general formula AxM2((Si,P)O4)3, which is adopted by hundreds of compounds. The balancing cations (A) are usually alkali or alkaline earth metals, and the structural metal(s) (M) a transition metal such as Ti, Zr, Nb, Cr, or Fe. The phosphorus can be substituted by silicon. The most famous member of this family is known as NASICON (from Na SuperIonic CONductor). This has proved to be a very good Na+ fast-ion conductor with a conductivity of 20 S m−1 at 300°C. It has the formula Na3Zr2(PO4)(SiO4)2 and three out of the four vacant sites are occupied by Na+, allowing a correlated motion as the ions diffuse through the channels. The structure of NZP (Na purple Si blue P brown/yellow O red).
Solid State Batteries
Published in P.J. Gellings, H.J.M. Bouwmeester, Electrochemistry, 2019
The sodium sulfur battery, also known as the beta battery, owes its existence to the remarkable properties of β-alumina as a fast ion conductor for Na+ ions. Discharge of the cell involves ionization of sodium atoms at the anode, followed by diffusion of Na+ ions through the wall of the β-alumina to the cathode where reduction of sulfur occurs. At temperatures of around 300°C the ionic resistivity of β-alumina (Na2O-11AI2O3) can be as low as 2 to 5 Ω cm, comparable to that of an aqueous sodium chloride solution, making it an ideal solid electrolyte for use in high-temperature Na batteries. The beta battery uses a molten Na negative electrode, the solid Na+ ion-conducting electrolyte, and a molten sulfur–sodium polysulfide mixture as the positive electrode. At 300 to 350°C, which is the required temperature, the Na/S cells must be sealed from the atmosphere to prevent reaction with water and air.
Functional Nanoceramics A Brief Review on Structure Property Evolutions of Advanced Functional Ceramics Processed Using Microwave and Conventional Techniques
Published in Sivashankar Krishnamoorthy, Krzysztof Iniewski, Nanomaterials, 2017
Santiranjan Shannigrahi, Mohit Sharma
Functional materials are considered as a group of smart materials that are distinctly different from structural materials. The physical and chemical properties of functional materials are sensitive to a variety of changes in the environment, such as temperature, pressure, electric field, magnetic field, optical wavelength, adsorbed gas molecules, and the pH value. These materials utilize their intrinsic properties to perform an intelligent action. Functional materials cover a broader range of materials than smart materials. Besides the materials belonging to the smart structure, any materials having functionality are attributed to functional materials, such as the ferroelectric BaTiO3 (perovskite), the magnetic field sensor of La1–xCaxMnO3, high-frequency microwave (MW) applications of Ni05Zn05Fe2O4 (ferrite) surface acoustic wave sensor of LiNbO3, liquid petroleum gas sensor of Pd-doped SnO2, semiconductor light detectors (CdS, CdTe), high-temperature piezoelectric Ta2O5, fast-ion conductor Y2(SnyTi1–y)2O7 (pyrochlore structure), the electric voltage-induced reversible coloring of WO3, and high-temperature superconductors. Functional materials cover a wide range of organic and inorganic materials. This chapter focuses only on oxide functional materials. Preparations of complex oxides with functionality are a key challenge for materials development. Searching new routes to prepare materials and understanding the relationship between the structures and the properties are equally important. A key requirement in preparation of materials is to control the structural and compositional evolution for achieving superior properties. Nanocrystal engineered materials are a new trend of materials research, aiming to improve the performances of materials.
Optical and electrical properties of Li2WO4 compound
Published in Phase Transitions, 2019
M. Krimi, K. Karoui, Joan Joseph Suñol, A. Ben Rhaiem
Since the existence of new problems like rarity, difficulties of extraction and the purity of the materials used, the attention of numerous industrial, electronic, scientific and medical works have been attracted to the exploration of new materials endowed with good thermal stability, possibility of recycling and health care. Among those materials, tungsten presents enormous resistance to heat (melting point is about 3380°C and the boiling point is about 5900°C). Moreover, tungsten-based compound is not considered hazardous to health. All those properties allow tungsten based materials to gain great interest owing to their important electrical, fluorescence, optical and dielectric properties [1–3]. Alkali metal, especially lithium and tungsten oxides, are widely used owing to numerous reasons (performing a chemical reaction, working media for heat storage media, etc.) [4–7]. These materials have been used in several fields of application such as luminophores, ferroelectrics, laser host materials, second harmonics generation, catalysts and solid electrolytes [7,8]. They have also gained momentum due to the fast ion conduction of small alkali ions through channels in the layered structures, leading to potential fast ion conductor materials [9–14]. Concerning the Li2WO4 compound, which is anhydrous, white-colored and thermally stable over a wide range of temperature up to the melting point of about 1015 K, the change in temperature and the method of preparation can affect the results obtained such as structure, phase transition and electrical properties [15–17]. A large number of compounds with the formula A2WO4 (A = Na, Li, K …) have been studied. Those materials generally possess a classical phenakite structure; however, this latter differs from one compound to another according to the monovalent criteria (mass, the ionic radius, etc.), displaying transitions phases at high temperatures [18]. Such materials present a good conductivity ensured by the monovalent cation [17]. In our work, the Li2WO4 compound was developed in order to study its electrical and calorimetric properties, as well as to define the conduction mechanism.