Melting tellurite glass with a gas mask

1
Processing and Characterization of Glasses
Mikayla Spitler1, Laeticia Petit2 and Kathleen
Richardson2 1 Nation Ford High School, 1400 A.O.
Jones Blvd., Fort Mill, SC  29715 2 School of
Materials Science and Engineering, Clemson
University, Clemson, SC 29634
Example xNaPO3-(100-x)Na2B4O7

• The goal of this project is to learn how
• to process three types of glass (non-toxic and
  toxic oxide, toxic non-oxide) and,
• to measure their density, thermal and optical
  properties.

Melt The chemicals are placed in a crucible and
melted at high temperatures.
Quench Prior to the quench, the liquid is mixed
to homogenize the glass. After re-melting, the
crucible is removed from the furnace and the
liquid is cooled very quickly to freeze the
liquid and prevent crystallization.
Anneal After quenching, the glass is heated at a
temperature below the melting temperature to
release the stress in the glass without forming
crystals.
Melting tellurite glass with a gas mask
COMPOSITION 70TeO2-10Bi2O3-20ZnO Toxic Raw
Materials
X
Chalcogenide Glass
COMPOSITION 90NaPO3-10Na2B4O7 Eu3
doped (90NaPO3-10Na2B4O7) Non-toxic Raw Materials
COMPOSITION Ge23Sb7S70 (oxygen free glass)
Batch preparation
Putting the crucible in the furnace for melting
Mixing
Thermal Properties
Quenching
Batch preparation A glove box filled with
nitrogen gas is used to limit oxygen in the batch
while weighing the raw materials.
Melting A rocking furnace, placed in the fume
hood, is used during melting to mix the
chemicals.
TUBES are used as Crucibles
Density
Combustion Tube

• Density formula
• rsample rdiethyl phtalate
  mass of sample (dry)
• mass of sample (dry) mass of sample
  (in liquid)
• - rsample density of the sample
• - rdiethylphthalate density of the
  diethylphtahlate at Temperature
• mass of sample (dry) the mass of the cleaned
  glass weighed in air
• - mass of sample (in liquid) the mass of the
  cleaned sample when immersed in the
  diethylphthalate
• Density of
• 90NaPO3-10Na2B4O7 (2.58 ?0.02) g/cm3
• Eu3 doped (90NaPO3-10Na2B4O7) (2.55 ?0.02)
  g/cm3
• 70TeO2-10Bi2O3-20ZnO (6.19 ?0.02) g/cm3
• Ge23Sb7S20 (2.93 ?0.02) g/cm3

• Equipment DTA instrument
• Materials 40mg of the glass in a crucible, a
  second crucible used as a reference
• Crucibles are heated at a heating rate of
  10oC/min
• Choice of crucible Pt, Alumina, Aluminum

Preparation
Example of a Thermogram
The glass transition temperature, Tg, is taken at
the inflection point of the endothermic signal
(also the minimum of the heat flow derivative)
Crystallization temperature, Tc, is measured at
the maximum of the exothermic signal SAFETY As
tellurite and chalcogenide glasses are toxic, the
crucible used for the measurement is an Aluminum
crucible which needs to be sealed prior to the
measurement HOWEVER, the crucible can only be
heated up to 475oC. ?
Sealed tube
Rounded end
Lighting the torch
Cleaning the samples prior to the measurement

• A combustion tube is used as a crucible during
  the glass melting
• The torch is used
• To cut and round the ends of the long glass tubes
• To seal the tube in vacuum

Tg
Tellurite glasses have the largest densities
because Te has the largest atomic radius
Tc
Optical Properties
UV Light Test
Equipment UV-Vis-NIR spectrometer Sample
preparation 2 parallel polished surfaces
Eu3 doped (90NaPO3-10Na2B4O7)

• Glass transition temperature of
• 90NaPO3-10Na2B4O7 (4002)C
• 70TeO2-10Bi2O3-20ZnO (3362) C
• Ge23Sb7S20 (3112)C

Eu3 doped (90NaPO3-10Na2B4O7)

• Under regular light, both samples appear to be
  the same
• However, in a UV light, the Eu3 doped glass has
  a pinkish coloration

Chalcogenide glasses have a lower Tg
Acknowledgements Robert Bowen, Kathy Bolton, Joel
Kohn, Jessica Green The GPCL group Kathleen
Richardson and Laeticia Petit Nathan Carlie,
Scott Gaylord, Jonathan Massera, Charmayne Smith,
Iona Moog, Alisa Stratulat
90NaPO3-10Na2B4O7
90NaPO3-10Na2B4O7
Absorption spectra give information about the
color of the glass and the position of the
absorption optical band gap related to P-O, Te-O
or Ge-S bonds