Functional Materials Lecture - Overview (PDF)

SCIENCE PASSION TECHNOLOGY Functional Materials – PHT.708UF Masters Program Technical Physics Functional Materials I – MAS.220UF Masters Pro...

SCIENCE PASSION TECHNOLOGY Functional Materials – PHT.708UF Masters Program Technical Physics Functional Materials I – MAS.220UF Masters Program Advanced Materials Science Masters Program Environmental System Sciences/Climate and Environmental Monitoring Dr. Stefan Topolovec Institute of Materials Physics 07.10.2024 Organizational remarks Organizational remarks ▪ Lecture dates ▪ Monday, 11:15-12:45, TDK Seminarraum ▪ Exception: Different room (HS 3.1, Petersgasse 10-12) on 16.12 ▪ TeachCenter ▪ Script ▪ Lecture slides (will be online already before each lecture unit) ▪ Links to references (for further reading) Functional Materials - Institute of Materials Physics 2 07.10.2024 Organizational remarks Organizational remarks ▪ Oral exam: ▪ A list with appointment dates will be offered at the end of the semester in TeachCenter ▪ For other dates: Please contact by email for individual appointment ▪ Consultation hours/questions: Please contact by email ([email protected]) Please make use of the possibility to ask questions during the lecture Functional Materials - Institute of Materials Physics 3 07.10.2024 Functional Materials Functional materials lecture - Overview 1. Electroceramics 4. Redox-flow batteries 5. Electrochemical 1. Electroceramics - Introductory overview capacitors/Supercapacitors of properties and applications 6. Fuel cells 2. Atomic structure of ceramic materials 7. Oxygen sensors 3. Basics of electronic properties of electroceramics 8. Hydrogen storage 4. Electroceramic devices 3. Superconducting 2. Energy materials materials 1. Brief overview of electrochemical 1. Introduction to superconductivity principles 2. Type-II superconductors 2. Li-ion batteries 3. High-temperature superconductors 3. Post Li-ion battery technologies Functional Materials - Institute of Materials Physics 4 07.10.2024 Functional Materials Functional materials lecture - Overview ▪ Previous Knowledge Expected ▪ Introduction to Solid State Physics ▪ Learning Objective ▪ The students understand the physical principles of functional materials and have gained insight in important applications of these materials, in particular in the field of electrical engineering, electronics and energy storage. Functional Materials - Institute of Materials Physics 5 07.10.2024  Chapter 1– Electroceramics Chapter 1: Electroceramics ▪ 1.1 Electroceramics - Introductory overview of properties and applications ▪ 1.2 Atomic structure of ceramic materials ▪ 1.3 Basics of electronic properties of electroceramics ▪ 1.4 Electroceramic devices References for Chapter 1 Elektrokeramische Materialien, 26. IFF-Ferienkurs (Forschungszentrum Jülich, ISBN 3-89336-146-4, 1995) A.J. Moulson, J.M. Herbert, Electroceramics (Chapman and Hall, London, 1990) K. Nitzsche, H.-J. Ulrich, Funktionswerkstoffe der Elektrotechnik und Elektronik (Deutscher Verlag für Grundstoffindustrie, Leipzig, Stuttgart,1993) Neue Materialien für die Informationstechnik, 32. IFF-Ferienkurs (Forschungszentrum Jülich, ISBN 3-89336-279-7, 2001) Functional Materials - Institute of Materials Physics 6 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications 1.1 Electroceramics - Introductory overview of properties and applications ▪ What are electroceramics? ▪ A ceramic is a non-metallic, inorganic solid ▪ Electroceramics can be defined as ceramic materials that have an useful electrical function ▪ Examples for electroceramic materials/applications Piezoelectric Dielectric Resistors ceramics ceramics Pyroelectric Ion-conducting Ferroelectrics ceramics ceramics Functional Materials - Institute of Materials Physics 8 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications Linear and non-linear resistors ▪ Oxide ceramics cover the whole range of electrical conductivity from insulators (e.g. Al2O3) to ceramic high temperature superconductors ▪ Linear resistors always provide the same resistance ▪ Ohms law is fulfilled ▪ Non-linear resistors change their resistance value with the applied voltage (varistor) or temperature (thermistor) ▪ Classification of thermistors: ▪ NTC thermistor (negative temperature coefficient): Resistance decreases with temperature rise ▪ PTC thermistor (positive temperature coefficient): Resistance increases with temperature rise Functional Materials - Institute of Materials Physics 9 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications ▪ Technically important resistors based on electroceramics Eur. Cerm. Soc. 38 (2018) 613. Source: M. Schubert et al., J. Type Example Physical effect T-dependent resistors NTC thermistors Spinels, Hopping conduction e.g. (in polaron (Ni,Mn)3O4 semiconductors) PTC thermistors n-doped Grain boundary →Overcurrent BaTiO3 phenomenon protection (in semiconducting ferroelectrics) (Cr,V)2O3 Metallic/semiconducting phase transition Voltage dependent resistors Varistors Modified Grain boundary → Overvoltage ZnO phenomenon arrester (in semiconducting ceramics) Linear resistors RuO2/glass Metallic conduction and composite grain-grain junction Functional Materials - Institute of Materials Physics 10 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications ▪ Technically important resistors based on electroceramics Eur. Cerm. Soc. 38 (2018) 613. Source: M. Schubert et al., J. Type Example Physical effect T-dependent resistors NTC thermistors Spinels, Hopping conduction e.g. (in polaron (Ni,Mn)3O4 semiconductors) PTC thermistors n-doped Grain boundary →Overcurrent BaTiO3 phenomenon protection (in semiconducting ferroelectrics) (Cr,V)2O3 Metallic/semiconducting phase transition Voltage dependent resistors Varistors Modified Grain boundary → Overvoltage ZnO phenomenon arrester (in semiconducting ceramics) Linear resistors RuO2/glass Metallic conduction and composite grain-grain junction Functional Materials - Institute of Materials Physics 11 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications ▪ Technically important resistors based on electroceramics Type Example Physical effect T-dependent resistors NTC thermistors Spinels, Hopping conduction e.g. (in polaron (Ni,Mn)3O4 semiconductors) PTC thermistors n-doped Grain boundary →Overcurrent BaTiO3 phenomenon protection (in semiconducting ferroelectrics) (Cr,V)2O3 Metallic/semiconducting phase transition Voltage dependent resistors Varistors Modified Grain boundary → Overvoltage ZnO phenomenon arrester (in semiconducting ceramics) Linear resistors RuO2/glass Metallic conduction and composite grain-grain junction Functional Materials - Institute of Materials Physics 12 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications ▪ Technically important resistors based on electroceramics Type Example Physical effect T-dependent resistors NTC thermistors Spinels, Hopping conduction e.g. (in polaron Lett-. Cerm. Soc. 59 (2005) 266. (Ni,Mn)3O4 semiconductors) Source: B.-K. Jang et al., Mater. PTC thermistors n-doped Grain boundary →Overcurrent BaTiO3 phenomenon protection (in semiconducting ferroelectrics) (Cr,V)2O3 Metallic/semiconducting phase transition Voltage dependent resistors Varistors Modified Grain boundary → Overvoltage ZnO phenomenon arrester (in semiconducting ceramics) Linear resistors RuO2/glass Metallic conduction and composite grain-grain junction Functional Materials - Institute of Materials Physics 13 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications Ferroelectrics Cubic phase, paraelectric ▪ Ferroelectrics have a spontaneous electric polarization ▪ Caused by non-centrosymmetric atomic structure, crystal without inversion center ▪ Important example: BaTiO3 (perovskite structure) ▪ The cubic phase has an inversion center and is paraelectric ▪ In the tetragonal distorted phase (stable below critical Tetragonal phase, temperature TC) the inversion center vanishes by the ferroelectric displacement of Ba2+ and Ti4+ ions relative to O2- ions ▪ Properties of BaTiO3 around its ferroelectric-paraelectric phase transition are used for several applications (e.g. PTC resistor or dielectric in ceramic capacitor) ▪ Other applications use ferroelectric materials (e.g. PbZrxTi1-xO3) in their ferroelectric state making use of their spontaneous polarization (e.g. FeRAM memories) Functional Materials - Institute of Materials Physics 14 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications Dielectric ceramics ▪ Ceramic materials with high specific resistance ▪ Applications ▪ Insulators and substrates (Al2O3, Si3N4) ▪ Dielectric material in ceramic capacitors (e.g. BaTiO3) ▪ Microwave dielectric components (e.g. Ba(Zn,Ta)O3 BZT): resonators, filters, antennas etc. for communication at microwave frequency Functional Materials - Institute of Materials Physics 15 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications Piezoelectric ceramics ▪ Piezoelectricity couples mechanical and electrical properties ▪ Direct piezoelectric effect: mechanical stress generates polarization Sensors (acceleration, microphone), generators ▪ Inverse piezoelectric effect: E-field induces mechanical deformation Actuators: − Positioning (linear) − Switching (valves, inkjet printers) − Resonant actuator (ultrasound generation) ▪ Important example: lead-zirconate-titanate (PZT) ▪ PbZrxTi1-xO3 ▪ Crystallizes in perovskite structure Typical dependence of strain on applied electric field Functional Materials - Institute of Materials Physics 16 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications Pyroelectric ceramics ▪ Pyroelectric effect: Flow of charges that results from the temperature dependence of the spontaneous polarization P ▪ Heat measurement via the variation of the polarization or dielectric constant with temperature ▪ Application: IR-detector for fire alarm systems, automatic light switches, thermal imaging cameras ▪ Important example: ferroelectric PbTiO3 Functional Materials - Institute of Materials Physics 17 07.10.2024 1.1 Electroceramics - Introductory overview of properties and applications Ion-conducting ceramics (solid electrolytes) ▪ Oxygen-ion conductors, especially Y2O3-doped ZrO2 ▪ Replacement of Zr4+ by Y3+ results in the formation of oxygen vacancies → enables fast diffusion ▪ Applications: High temperature fuel cell Oxygen sensor (λ-sensor) (Solid oxide fuel cell) Measurement of air/fuel ratio ▪ Li-ion conductors ▪ Used as solid state electrolyte for Li-ion batteries ▪ e.g. ceramic sulfide Li10GeP2S12 (LISICON structure: LIthiumSuperIonicCONductor) Functional Materials - Institute of Materials Physics 18 07.10.2024 1.2 Atomic structure of ceramic materials 1.2 Atomic structure of ceramic materials ▪ 1.2.1 Crystal structure ▪ 1.2.2. Point defects in ceramics Functional Materials - Institute of Materials Physics 19 07.10.2024  1.2.1 Crystal structure 1.2.1 Crystal structure ▪ Ceramic materials are mostly ionic compounds made up of metals (→ cations) and non-metals (→ anions), particularly oxygen (oxides) and nitrogen (nitrides). ▪ Oxides consist of a regular arrangement of O2- with cations occupying either O2--sites or interstitial sites ▪ Important examples of structure of ionic compounds NaCl structure Fluorite structure (CaF2) FCC lattice with two atom basis FCC lattice of Ca2+,,F- occupy tetrahedral interstitial sites MgO, CaO, TeO2, FeO, NiO cubic ZrO2 Sources: https://commons.wikimedia.org/wiki/File:Sodium-chloride-unit-cell-3D-ionic.png Functional Materials - Institute of Materials Physics https://commons.wikimedia.org/wiki/Category:Crystal_structure_of_fluorite#/media/File: 20 07.10.2024 Fluorite-unit-cell-3D-ionic.png 1.2.1 Crystal structure ▪ The crystal structure has to be charge-neutral and has to enable an efficient packing of ions of different size triangle ▪ In general the ionic radius of the cations (rc) is smaller than tetrahedron the ionic radius of the anions (ra) ▪ The coordination number octahedron decreases with the difference in size, i.e. with decreasing radius ratio rc/ra cube dodecahedron Sources: https://commons.wikimedia.org/wiki/File:Sodium-chloride-unit-cell-3D-ionic.png Functional Materials - Institute of Materials Physics https://commons.wikimedia.org/wiki/Category:Crystal_structure_of_fluorite#/media/File: 21 07.10.2024 Fluorite-unit-cell-3D-ionic.png 1.2.1 Crystal structure triangle tetrahedron octahedron cube dodecahedron Functional Materials - Institute of Materials Physics 22 07.10.2024 1.2.1 Crystal structure triangle tetrahedron octahedron cube dodecahedron Functional Materials - Institute of Materials Physics 23 07.10.2024 1.2.1 Crystal structure Rutile structure (TiO2) ▪ Tetragonal cell ▪ 2 Ti4+ at (0,0,0) and (0.5,0.5,0.5) triangle ▪ 4 O2- at (0.3,0.3,0), (0.7,0.7,0), (0.8,0.2,0.5) and (0.2,0.8,0.5) tetrahedron ▪ Coordination number for Ti4+ ions: 6 octahedron ▪ r(Ti4+ )/r(O2-)=65pm/140pm=0.46 cube dodecahedron Functional Materials - Institute of Materials Physics 24 07.10.2024 1.2.1 Crystal structure Perovskite structure (CaTiO3) ▪ General form: ABO3 ▪ rA> rB (rA , rB…radii of cation A and B) ▪ Cubic unit cell ▪ A cations at corner ▪ B cation in body center ▪ O2- anions occupying the face centers ▪ Coordination numbers ▪ A cation: 12 ▪ B cation: 6 ▪ Possible cation charge ▪ A3+B3+O2-3 ▪ A2+B4+O2-3 The smaller cation always carries the higher charge ▪ A1+B5+O2-3 Functional Materials - Institute of Materials Physics 25 07.10.2024 1.2.1 Crystal structure Perovskite structure (CaTiO3) - Distortions ▪ In dependence on the radius ratio of the cations distortions from the cubic structure appear ▪ Note: The name perovskite structures is used for the cubic structure as well as for the distorted structures ▪ Ideal packing (cubic structure) occurs for ▪ The tolerance factor t describes the deviation from ideal packing ▪ Cubic structure for about 1 > t ≥ 0.9 ▪ (Distorted) perovskite structures are stable for 1 > t ≥ 0.7 Functional Materials - Institute of Materials Physics 26 07.10.2024 1.2.1 Crystal structure Perovskite structure (CaTiO3) - Distortions ▪ Example: Distortions of A2+B4+O2-3 perovskites – phase diagram ▪ The stable structure can be determined by the phase diagram shown below considering the ionic radii rA and rB SrTiO3: cubic structure CaTiO3: orthorhombic distortion BaTiO3: at cubic/tetragonal transition → Cubic or tetragonal phase is stable dependent on temperature Functional Materials - Institute of Materials Physics 27 07.10.2024 1.2.1 Crystal structure Perovskite structure - Structure of BaTiO3 ▪ Above critical temperature TC (108 ℃): ▪ Ideal cubic perovskite structure ▪ Structure has inversion center → paraelectric ▪ Below critical temperature TC : ▪ Tetragonal distorted perovskite structure ▪ Spontaneous electric polarization due to distortion → ferroelectric Source: https://commons.wikimedia.org/wiki/File:Perovskite.svg Functional Materials - Institute of Materials Physics 28 07.10.2024