Alkali-lead glasses Flashcards

1
Q

What are the characteristics of lead oxide glasses?

A

~ lead oxide additions VASTLY INCREASE DENSITY

~ PbO substitution for Na2O DECREASES ionic conductivity via less mobile Na+ conc.

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2
Q

Why is lead an exception to the rule for cations?

A

~ the e- cloud for Pb2+ polarizes in response to electric field

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3
Q

What happens at high conc. of PbO?

A

~ Pb4+ takes the role of a network former w/ tetrahedral coordination of oxygen

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4
Q

What are applications for alkali-lead glasses?

A

~ highly reflective
~electrical feedthrough and sealing
~ high XRAY absorption, crt/tv screens

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5
Q

What happens when lead acts as a network former?

A

~ as a network former, glass has more covalent bonding and more open network to vibrate = LOW CTE

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6
Q

What is the equation for reflectance?

A

= [(nair - nglass)/(nair+nglass)]^2

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