(A by far not complete selection of)

Fundamental data & processes related to the materials in light sources

(what manufacturers need)

Zoltán TóthGE Consumer & Industrial, Budapest

Manufacturers aims

• Initial Light output & Efficacy

• Maintenance during lamp life - Light output - spectral distribution/color spread - Efficacy

• Optimized/better Light quality

- color/white light/reaction time/safety

- color research/McAdam ellipses

- new applications: medical, food quality, training, dimming studies,…

- novel light source families: exotic discharges, LEDs,…

• Costumer wants better ‘illumination

Better fulfil of costumer’s needs

• price

- new materials & processes

• Cost of light

• lifetime, Reliability

• RoHS, WEEE

Manufacturers constraints

Material Science: properties and novel materials

High Intensity Discharge (HID) Technology

Plasma physics : discharge models& diagnostics• see this workshop • radiative processes• electrode-plasma coupling

• Discharge Chemistry, Thermochemistry

• Materials• electrodes• ceramics• ceramic-metal interfaces

• Lamp/Ballast Interaction

• Processes and Equipment

Key science and technology areas :

Material Science: properties and novel materials

Electrode system Electron emission properties

• work function • thoriated system: RoHS concern?• composition & chemistry on the surface• electrode-plasma interaction• diffusion processes inside the electrode

0 5 10 15 20 25 30

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200000

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300000

c)

e)d)

a)

b)

SEE

Inte

nsity

(CPS

)

Kinetic energy (eV)

WFS:• Mapping (lateral resolution of ~5m)• Time dependent changes during heat treatment and/or gas exposure

But• geometrical effect (positioning)• polished surface or correction• effect of ion bombardment• connection to operating condition

• beside lighting: welding electrodes

Electrode system Electron emission properties• work function • thoriated system• composition & chemistry on the surface• electrode-plasma interaction• diffusion processes inside the electrode

• electrical parameter stability• starting processes

• sputtering, evaporation• deposits on the wall• Starting

• sputtering• kinetic : do we have enough energy ?• electronic : do we have this in oxides ? (energy level of electrode/e-mix, photons)• effect of the discharge atmosphere (dose, fill pressure)• effect of the electrode material (dopants, crystal structure)• effect of the e-mix material (if applied)

• connected diagnostic tools : glow, glow to arc transition, temperature and charge distribution

• Steady state operation : evaporation or desorption of the adatoms

Ceramics

• Light Scattering• pores (inter- and intra granular)

• dopants (MgO, Y2O3, ZrO2,…)• grain boundaries

• hexagonal : birefringence• large grain size reduces strength• saphire

• Chochralski• solid state conversion

• cubic lattice crystals• sub-micron grain size

• surface• polishing

• Transparent ceramics for better optics• beside lighting: bullet proof window

Glass-metal and ceramics-metal interfaces

• thermal expansion properties • modulus of elasticity• tensile strength• Poisson ratio• Critical Apparent Fracture Toughness• Stress behaviour at phase interface and at voids

• summing rules for FEM studies• what is the optimal seal structure

Radial (X)

Tangen

t (Z)

Stresses

Glass-metal and ceramics-metal interfaces: corrosion

Arc tube

Pinch Molybdenum foil

• Reactive Metal halide salts: corrosion of molybdenum feedtrough foils• NaI reacts with molybdenum and forms Na2MoO4 • InI does not react with molybdenum, but diffuses into the deeper layers

• Ceramics corrosion • composition and vapour pressure of the complexes• reaction of complexes with wall materials