What a ceramic is ?
From Greek word “keramos” (pottery, potter’s clay)
Inorganic nonmetallic materials obtained by the action of heat and subsequent cooling
Polycrystalline materials, single phase or multiphase (composites), sometimes with an amorphous component (glass)
Traditional ceramics
•Whitewares: tableware, cookware, sanitary ware, etc.•Refractories (kiln and furnace linings for steel and glass industry)•Structural clay products (floor & roof tiles, bricks, etc.)
Fabricated from clay, quartz, feldspar (earthenware) and kaolin (porcelain)
Technical/advanced ceramics
•Structural ceramics (mechanical properties: strength, toughness, hardness, creep resistance)•Functional ceramics (electric, magnetic, optical properties)
Structural ceramics
•Si3N4: bearing balls, cutting tools, heat exchangers, turbocharger rotors, parts of
gas turbines
•SiC: abrasives, disk brakes, pipes for corrosive liquids, ballistic armors
•WC, Ti(C,N): cermets, inserts for cutting tools
•B4C: neutron absorber in nuclear plants, ballistic armors, nozzles, abrasives
•Al2O3 (alumina): spark plugs, substrates, crucibles, furnace tubes, ballistic armors,
thermal insulation
•3Al2O3•2SiO2 (mullite) & Mg2Al3(Si5AlO18) (cordierite): catalytic converters, ceramic
filters
•ZrO2 (zirconia): knifes, watch cases, orthopedic implants, grinding media, thermal
barrier coatings
•UO2: nuclear fuel
•Ca10(PO4)6(OH)2 (hydroxyapatite): biomedical implants, artificial bone
Ceramic Si3N4 bearing parts
Radial rotor made from Si3N4 for a gas turbine engine The Porsche Carrera GT's
silicon carbide disk brake
Two Kyocera ceramic knives Ceramic body armour plates
Functionality Material Applications
Resistors SiC, MoSi2, LaCrO3 Heating elements for high temperature furnaces
Thermistors
(NTCR & PTCR)
Spinels
BaTiO3
Temperature sensors, self-regulating heating elements
Dielectrics with very low losses (r = 3 -10)
Al2O3, AlN, cordierite
Substrates for electronic circuits and chip packaging
Dielectrics for microwave applications (r = 30-80)
BaTi4O9, Zr(Ti,Sn)O4, BaMg1/3Ta2/3O3,
(Ba,Sr)TiO3,
MW resonators, filters and antennas for mobile communications and GPS devices, tunable MW devices
Temperature stable dielectrics (r 100)
CaTiO3, BaO-Nd2O3-TiO2
Capacitors with temperature-independent capacitance
Dielectrics with very high dielectric constant (r 3000)
BaTiO3 Multilayer ceramic capacitors
Piezoelectric ceramics Pb(Zr,Ti)O3 (PZT) Transducers, actuators and resonators
Pyroelectric ceramics Pb(Zr,Ti)O3 IR radiation detection and imaging
Functional ceramics
Functionality Material Applications
Ferroelectric ceramics
Pb(Zr,Ti)O3
SrBi2Ta2O9
Ferroelectric memories (FeRAMs)
Electrostrictive ceramics
PbMg1/3Nb2/3O3 -PbTiO3 (PMN-PT)
Actuators
Magnetic ceramics Spinels (Ni,Zn)Fe2O4
BaFe12O19
Y3Fe5O12 (YIG)
Inductors
Permanent magnets
Microwave devices (radars)
Ionic conductors Y:ZrO2 (YSZ)
Gd:CeO2
β-alumina
Electrolytes for solid-oxide fuel cells (SOFCs), oxygen sensors
Na-Batteries
Superconductors YBa2Cu3O7-x (YBCO)
MgB2
Superconducting cables for magnets
Transparent ceramics
Al2O3, MgAl2O4, Y3Al5O12 (YAG)
Phosphors, optical materials for lenses and laser systems, nose cones for heat-seeking missiles, high-pressure sodium street lamps
Optoelectronic materials
LiNbO3
PLZT
Waveguides, frequency doublers, voltage-controlled optical switches, modulators
Functional ceramics
Thick (left) and thick (right) substrates (alumina)
Pressed and extruded parts (alumina, mullite, zirconia)
Ferrites cores Microwave dielectric components
Ceramic microstructures
SSS 99% Al2O3 – transparent fully dense (“ideal”) ceramic: grains + grain boundaries
SSS 99% Al2O3 - ceramic with residual porosity: grains + g.b. + pores
LPS 96% Al2O3 - dense ceramic with grain boundary glass phase: grains + glassy phase (CaO*SiO2) + 2 types of g.b.
Microstructural variables
Density - crystallographic (from unit cell parameters)- theoretical (zero porosity, takes into account real composition)- apparent (geometrical) density (< theoretical)- relative density = (apparent/theoretical)*100
Porosity- closed (only closed above 93% r.d.)- open (pore networks connected to the surface)- intragranular- intergranular
Grain size (simplest method: mean intercept length) Grain size distribution (monomodal, bimodal, abnormal grain growth) Grain shape (equiaxed, elongated, prismatic, columnar, tabular, platelets)
- aspect ratio (ratio longest/shortest size dimensions)
Extended defects (dislocations, stacking faults, twins, domain walls)
Second phase composition, shape and distribution
Texture (grains oriented in a preferential direction)
Intergranular porosity
Intragranular porosity
Y2O3:ZrO2 (PSZ) ceramicIntra- and intergranular porosity
Ba(Ti,Ce)O3 ceramicClosed (intragranular) and open (itergranular channels) porosity
Types of porosity
Equilibrium shape of grains. Hexagons (2D) and truncated octahedron (3D)
gb
gbgb
120°
Shape of grains and pores
Concave pore Convex pore Irregular pore associated with a hard agglomerate
Grain size distributions and abnormal grain growth
1450°C/2 hEquiaxed grains with monomodal distribution
1500°C/2 hSome large elongated grains appear: onset of AGG
1550°C/2 hBimodal distribution related to AGG
Mg0.1Al1.8Ti1.1O5 ceramics
FractographyPolished surface
Cross-sections of Ba(Ti,Zr)O3 ceramics
Grain pull-out
Revealing microstructure
Chemical etching
Si3N4
Fully-dense alumina
Thermal etching
SiC
Revealing microstructure
Er-doped BaTiO3
Solid grain Solid grain
Vapour
After polishing
After thermal treatment
Spectrum In stats. O Ti Ba Ce Total 1 Yes 23.43 9.37 58.72 8.48 100.00 2 Yes 22.41 2.77 41.71 33.11 100.00
Scanning electron microscopy using backscattered electrons (BEI)
Al2O3-(Zr,Y)O2 compositeThe darker phase is alumina
Ba(Ti,Ce)O3 ceramic containing Ce-rich inclusions
Secondary phases in Er-doped BaTiO3
White phase: Er2Ti2O7
Dark gray phase: Ba6Ti17O40
Revealing microstructure