PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Inorganic chemistry → Solid state chemistry ↓


Solid state ionics


Solid-state ionics is an interesting branch of solid-state chemistry that focuses on the study of ionic motion within solids. In essence, it looks at how ions (charged particles) move around in solids. This field plays a key role in the development of advanced materials and technologies, such as solid electrolytes for batteries, fuel cells, and sensors. To understand solid-state ionics, it is important to delve deeper into the mechanisms that allow ions to move, the types of materials involved, and their applications.

Fundamentals of solid state ionics

At the core of solid state ionics is the concept of ionic conduction, which refers to the movement of ions through a crystal lattice. Unlike electronic conduction, where electrons move through a material, ionic conduction is characterized by the transport of ions. The efficiency of ionic conduction depends on several factors such as the type of ion, the structure of the material, and temperature.

Ionic transport mechanisms

Ionic movement can occur by a variety of mechanisms. A common mechanism is vacancy diffusion, where ions move from one vacant site to another within the crystal lattice. Another mechanism is interstitial diffusion, where ions move through gaps or interstitial sites in the lattice. Frenkel defect and Schottky defect are two types of defects that facilitate ionic movement:

  • Frenkel defect: In this the ion leaves its normal lattice site and moves to an interstitial site, thereby creating a vacancy.
    X XXX -> XXXX XXXXXX XXX -> XXXX XXXXX
  • Schottky defect: This defect arises when equal number of cations and anions leave their lattice points and form vacancies.
    XXX -> XX XXXXX XXXXXXXX -> XX XXXXX XXXXX

Factors affecting ionic conductance

Ionic conduction in solids is affected by structural and external factors. Key factors include:

  • Crystal structure: The arrangement of ions in a crystal lattice affects the ease of movement of the ions. Structures with larger lattice spacing or more defects generally allow better ionic conduction.
  • Temperature: Higher temperatures generally increase ionic mobility because thermal energy overcomes energy barriers to diffusion.
  • Defects: Intrinsic and extrinsic defects facilitate ionic movement by providing vacant spaces or easy pathways for ions.

Included ingredients

Various materials are known for their ionic conduction properties, ranging from ceramics to polymers. Some of the major types are as follows:

Ceramic ionic conductor

Ceramics are commonly used in ionic conductors due to their high durability and stability. For example, zirconia oxide doped with yttrium oxide, ZrO_2 - Y_2O_3, is well-known for its high oxygen-ion conductivity.

Polymer electrolytes

Polymers can also exhibit ionic conductivity by dispersing salts within them. These materials are often used in flexible battery technologies. Polyethylene oxide (PEO) with lithium salts is a typical example.

Glass electrolytes

Glasses are amorphous solids that can facilitate ionic movement due to their disordered structure, giving high ionic conductivity. Sodium superionic conductor (NASICON) glasses, with the formula Na_1+xZr_2(SiO_4)_x(PO_4)_{3-x}, are widely recognized in this regard.

Application

Solid state ions have widely important applications in modern technology, especially in the field of energy storage and conversion.

Batteries

Solid-state batteries use solid electrolytes to transport ions from the anode to the cathode. They promise greater safety and energy density than traditional liquid electrolyte batteries. A popular type of solid-state battery is the lithium-ion battery which uses solid ceramic electrolytes such as Li_4Ti_5O_{12}.

Fuel cells

Solid oxide fuel cells (SOFCs) use ceramic materials to conduct oxygen ions. These cells provide efficient energy conversion using both renewable and conventional fuels.

Sensor

Ionically conductive materials can also be used in sensors, especially those used to detect gases such as carbon dioxide or oxygen. These sensors often rely on changes in ionic conductivity to detect and measure gas concentrations.

Theoretical approach

Understanding and predicting ionic motion in solids often requires theoretical modeling. Mathematical models such as the Nernst-Planck equation and molecular dynamics simulations help provide insight into ionic conduction processes.

Nernst–Planck equation

Describes ion transport in substances driven by a concentration gradient and an electric field:

J_i = -D_i (dC_i/dx) - (z_i F C_i/RT) (dϕ/dx)
Where J_i is the ionic flux, D_i is the diffusion coefficient, C_i is the concentration, z_i is the charge number of the ion, F is the Faraday constant, R is the gas constant, T is the temperature, and dϕ/dx represents the electric field.

Molecular dynamics simulation

Simulations provide a powerful tool to observe ionic motion at the atomic level and can help predict material properties and performance.

Challenges and future directions

Despite significant progress in the field of solid state ionic devices, many challenges remain, including the difficulty of achieving high ionic conductivity at room temperature and the costly synthesis of some solid electrolytes. Researchers are constantly exploring new materials and designs to improve the efficiency, cost-effectiveness, and scalability of solid state ionic devices.

Room-temperature conductivity

Developing materials that maintain high ionic conductivity at room temperature is important. Research is focused on understanding the relationship between structure and conduction to discover new materials.

Interface stability

Increasing the stability of the interface between different phases, such as the electrolyte-electrode in batteries, is critical for long-term performance. Advanced analytical techniques and improved material design can provide solutions.

Durable material

Exploring environmentally friendly and sustainable materials for ionic conductors aligns with global efforts for green technologies. The emphasis is on the abundant use of less hazardous raw materials.

Conclusion

Solid state ionics is a cornerstone of modern materials science, providing insights and solutions for a variety of technologies that are central to enhancing energy systems and electronic devices. The continued exploration of ionic mechanisms and materials opens exciting opportunities for future innovations.


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Solid state ionics

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