Alkali-lead glasses Flashcards
What are the characteristics of lead oxide glasses?
~ lead oxide additions VASTLY INCREASE DENSITY
~ PbO substitution for Na2O DECREASES ionic conductivity via less mobile Na+ conc.
Why is lead an exception to the rule for cations?
~ the e- cloud for Pb2+ polarizes in response to electric field
What happens at high conc. of PbO?
~ Pb4+ takes the role of a network former w/ tetrahedral coordination of oxygen
What are applications for alkali-lead glasses?
~ highly reflective
~electrical feedthrough and sealing
~ high XRAY absorption, crt/tv screens
What happens when lead acts as a network former?
~ as a network former, glass has more covalent bonding and more open network to vibrate = LOW CTE
What is the equation for reflectance?
= [(nair - nglass)/(nair+nglass)]^2