Materials Used in Lamp Bulb

Various types of material are used to build a lamp. Insulating materials, conducting materials are the essential parts of a lamp set up. The details of those materials are given below.Glass

• As it is a transparent material, used as barrier. Light gets various colors depending on the color of the glass.
• It with stand the pressure of the gas inside the lamp.
• It is chemically no reactive and used to maintain the lamp as the thematic shield.

The types of the glass vary based on their composition.

Soda Lime Silicate (Soda Glass)

• It has low melting point
• It is used in filament lamp.
• It is used with 67 % SiO₂.

Lead Alkali Silicate

• It is used in the inner portion of the bulb glass.
• It has higher electrical resistivity.

Borosilicate Glass

• It used in higher wattage lamp, ex- cinema projector.
• It has higher temperature with stand capability.
• Thermal expansion co-efficient is very low.

Alumina silicate Glass

• It has lower thermal shock capability than borosilicate glass.
• It is used for low wattage lamp with most refractory convention.

Quartz

• It is used in tungsten halogen Lamp.
• It is transparent silica and pure silicon dioxide.
• It is having only ppm of other metals and OH^- group ion.

Sodium Resistant Glass

• It is used for Na vapor lamp.
• Powerful reducing property of Na vapor produces rapid blackening. In normal glasses it happens. So small amount of silica or other readily reducing oxide is mixed with it.
• It has strain throughout life.

Ceramics

• The modern technology helped to develop to produces poly crystalline metal oxide bodies.
• Oxide made ceramics transparent or translucent.
• It includes alumina, magnesia; they are very rare earth oxides.
• It is pore free structure and permits the visible rays to transmit through it.
• In the high pressure lamp, they are being used because of transmitting light.
• In poly crystalline translucent lamp and poly crystalline alumina lamp ceramics are used.
• Ceramics are used as enclose material in high pressure Na and metal halide Lamp.

Conventional Ceramics Conventional ceramics are of two types, porcelain and steatite.

Porcelain

• Porcelain is used to make base or the end cap.
• It has good mechanical strength
• It possesses good thermal shock resistance and good electrical insulating property.
• It is having good resistance of attack of moisture.

Steatite

• It is better than porcelain.
• It is made of talk, clay, small amount of alkali and alkaline earth oxide.

Metal

Tungsten

• Its ore is Scheelit(CaWO₄), wolframaite (FeMn)WO₄
• By chemical process tungsten is extracted and made it into the wire.
• Tungsten wire is wound on either on iron or molybdenum mandrel to make coil filament.
• Impurities (C, O, Fe, N) are strictly controlled to make this coil filament.
• By mixing AKS (Al, K and Si ) extreme accuracy in coil geometry.
• Tungsten is mostly used in miniature lamp.
• This coil is coated with alkaline earth oxide.

Molybdenum

• Its melting point is 2610^oC.
• It is used to support the filament coil.
• Its coefficient f expansion matches some categories of glasses.
• It is used in glass metal shield in many cases.

Nickel

• It is used in electroplating iron and steel.
• Small percentage of nickel with iron and steel increases the hardness and elasticity.
• Nickel steel combination has higher resistance against corrosion.
• It is used in lead in wire.
• In bi metallic strip of starter nickel is also used.

Aluminum

• This metal is non ferrous light weighted and non magnetic material.
• It is with high corrosion resistance.
• It has high ductility and malleability.
• It is easily available.
• Cheap in price,
• Aluminum cap is used in suspended lamps.
• It forms a small thick oxide layer.
• It does not corrode easily with normal weather.
• In many cases it is used to make good reflector.

Steel

• In a structural portion steel is used for fabrication of light equipment.
• Steel sheet has higher strength and lower cost.
• Hot rolled, cold rolled and porcelain enameling sheet are the types of steel.
• Hot rolled steel is used where smooth appearance is desired.
• Cold rolled is used in case of thinner portion with smooth surface appearance.
• Porcelain enameling has very less carbon content.

Stainless Steel

• It includes iron based alloys which contains sufficient chromium.
• It has higher resistance against corrosion.
• Its classification is based on presence of chromium from 12% to 30%.
• It is used in the luminaries, especially outdoor purpose where is a chance of presence of corrosive atmosphere.

Copper

• In conductor this metal is used extensively.
• In Bas bar, switch gear copper is also used.
• It ductile and malleable & strong material.

Non Ferrous Alloys

• Bronze (Cu + Sn), Brass (Cu + Zn) are non ferrous alloys.
• They are used in special luminaries.
• They have attractive color appearance.
• They are highly resistive against marine water.

Solder

• It is the alloy of Sn and Pb.
• It holds on to a surface.
• It is used at the end of the lamp cap for electrical connection.

Getter Material

• This material is used to absorb the gas as impurity produced inside the lamp during operation, as the produced gas lower the lamp performance.
• O₂, CO₂, CO etc are produced inside the shielded lamp bulb and they are known as getter.
• Getter material can be in the form of sheet or wire or surface deposit etc.
• Barium, tantalum, titanium, niobium, zirconium and some of their binary alloys are known as metallic getter.
• Red phosphor is known as non metallic getter material.