New High Zirconia fused cast material for high quality glass without low temperature oxygen blistering ICF Technical meeting, Sienna November 05th , 2007

Topics of the presentation New High Zirconia fused cast material for high quality Glass without low temperature oxygen blistering Topics of the presentation Main interest of HZFC material in high quality glass Low temperature oxygen blistering phenomenon Hypothesis of mechanism with HZFC How to prevent oxygen blistering Properties of new HZFC Influence of crystal glass composition evolution regarding AZS and HZFC materials

Interest of HZFC in quality glass 1 Interest of HZFC in quality glass

High Zirconia Fused Cast Microstructure Typical composition microprobe mapping Al2O3: 0.4 - 2 % ZrO2 > 90 % SiO2: 3 - 7 % Na2O: 0 – 0.4 % B2O3: 0 – 1 % Al2O3 SiO2 ZrO2 Zirconia Glassy phase Na2O 100 µm

Fused Cast AZS Microstructure Typical composition microprobe mapping Al2O3: 46 % ZrO2: 41% SiO2: 12 % Na2O: 1% Al2O3 ZrO2 Zirconia Glassy phase Corundum / Zirconia eutectic Na2O SiO2

Main interest of using HZFC material Low level of glass contact defects low level of Crystallized or vitreous defect origin of defects in convective area as : Clear Knot HZFC AZS (41% ZrO2) Leucite (Al203-K2O-4SiO2) with zirconia nodule 10% Al203, 2% ZrO2, 11% PbO, 16%K2O, 0.8% Na2O Glass contact AZS interface, primary ZrO2

Main interest of using HZFC material Low level of glass contact defects low level of blistering at high temperature Test condition : TV/PDP glass, Temperature :1450°C, Duration :70H Crucible test AZS (41% ZrO2) HZFC

Low temperature oxygen blistering phenomenon 2 Low temperature oxygen blistering phenomenon

low temperature oxygen blistering phenomenon High quality glass  extended use of HZFC materials in the furnace final part (fining, feeder, …) To solve some corrosion problem (borosilicate, crystal glass …..) To prevent Glass contact defect related to chemical composition of the glass (compare alpha/béta alumina product, or AZS product ) Glass SiO2 Na2O K2O CaO Ba0 SrO MgO Al2O3 ZrO2 Wt % 58-69 4 – 5 5 – 7 5 - 10 1 – 8 0 – 2 1 – 7 2 – 4 Oxygen blistering phenomenon

Low temperature oxygen blistering phenomenon Blistering phenomenon with high efficiency Blistering crucible test at 1120°C , 30 hours , alkali test glass Necessary conditions to obtain high oxygen blistering Air outside crucible Temperature < 1130°C Alkalii inside the glass

Low temperature oxygen blistering consequences HZ Electrical furnace 1250°C bubble defect in glass Corrosion enhancement by upward drilling phenomenon Glass cold area glass Oxygen blistering in the join ( low temperature area )

Hypothesis of this phenomenon 3 Hypothesis of this phenomenon

Low temperature oxygen blistering mechanism : High temperature dependence of this phenomenon related to zirconia crystallographic transformation Monoclinic zirconia Quadratic zirconia Thermal expansion % Temperature 1120-1140°C

Low temperature oxygen blistering mechanism : Conductivity process change with zirconia transformation Electrical conductivity process change with temperature at the zirconia crystalographic transformation

Activation energy increase after zirconia transformation Low temperature oxygen blistering mechanism : -14 -12 -10 -8 -6 -4 -2 1E-04 2E-04 3E-04 4E-04 5E-04 6E-04 7E-04 8E-04 9E-04 0,001 0,002 1/T(K°) Ln sigma (ohm-1.cm-1) ER 1195 Activation energy increase after zirconia transformation Arrhenius diagram : Log(sigma) = f(1/T) for zirconia contribution Electronic to ionic conductivity change at the zirconia temperature transformation

Oxygen Blistering mechanism Hypothesis Refractory wall réduction Reaction M Y+ + x e-  M y-x glass Oxydation 2 O2-  O2 + 4 e- e- Na+, K+ Electro chemical process that can take place because of: alkali available in the glass electronic conductivity in the refractory at T<1130°C oxygen outside of the crucible that could be reduced (or that could reoxydized impurities)

How to prevent low temperature oxygen blistering with HZFC 4 How to prevent low temperature oxygen blistering with HZFC

How to prevent low temperature blistering in glass Deformation % Y2O3 addition Monoclic zirconia Quadratic zirconia Temperature Glass crystallization temperature

How to prevent low temperature oxygen blistering Y2O3 addition that allow to : lower the electronic conductivity temperature area Stay stable with temperature Doesn’t react with alumina or silica inside the glassy phase Form solid solution with zirconia Microprobe mapping of Y2O3

(Higlh quality display panel glass ) Y2O3 necessary level is related to glass crystallization curve (Higlh quality display panel glass ) Y2O3 target = [ 0.8 – 1%]

Sensible shift of zirconia transformation temperature with Y2O3 addition Need to adapt the glassy phase composition to the lower reverse temperature transformation during the annealing process of the block

Glassy phase modification with Y2O3 addition Glassy phase properties measurements in the SiO2-Al2O3-Na2O-Y2O3 system  simulation Thermal expansion Glass transition temperature, crystallization High température viscosity To design the right level of SiO2, Na20 and Al2O3 for a given Y2O3 %

New HZFC materials : First industrial results Cut block Low level of internal defect SiO2 = 4 – 6 %, Al2O3 = 0.7 -1.2 %, Na2O = 0.4- 0.8%, Y2O3 = 0.8 – 1%

High alkalii test glass High alkalii test glass Blistering test results on industrial products : Crucible test : 1100°C , 30 hours HZFC Display panel glass High alkalii test glass New HZYFC Display panel glass High alkalii test glass No oxygen bubles with the new product at 1100°C

High alkalii test glass High alkalii test glass Blistering test results on industrial products : Crucible test : 1000°C , 30 hours HZFC Display panel glass High alkalii test glass New HZYFC Display panel glass High alkalii test glass No oxygen blistering up to 1000°C with new HZFC Secure solution with display panel glass (no blistering up to crystallization temperature)

Glass contact properties 5 Glass contact properties

Static corrosion test (T-test) HZFC New HZFC stone (droplet ) 1-2 Stone (crucible) 0-1 Indice global 1 Conditions of the test : Temperature : 1500°C Duration : 48 heures Glass : PDP

Dynamic corrosion test (test MGR) HZFC New HZFC Indice 100 105 83 88 Conditions d’essais : Température : 1500°C Duration : 48 heures Glass : PDP

6 Influence of crystal glass composition evolution regarding AZS and HZFC materials

Crystal glass composition evolution  Evolution to lead free Glass   Typical PbO Crystal Glass Lead free Glass (BaO) (w/o BaO) Na2O 3-5 7,5-11 8,6-10,9 K2O 10-14 5-7 8,7-10 BaO 5,9-8,9 Al2O3 <0,05 0,4-3,4 1-2 ZnO 0-2 0,9-2,3 2,3-5,5 PbO 25-32 CaO 2-6 4-6 TiO2 1-1,7 SiO2 in complement First family : lead free glass with BaO addition, ( increase of Al2O3, CaO, Na2O, decrease of K2O ) Second family: lead free glass without BaO, with main addition of ZnO, TiO2

Glass evolution impact of refractory corrosion Not working at iso viscosity HZFC AZS (41% ZrO2) Corroded Volume (cm3) Index Crystal Glass 2,62  53 1,41  100 Lead free Glass (BaO), 3.85 79  3.09   100  Lead free Glass (W/o BaO) 4,53 63 2,88 Tests conditions : Diameter: 22 mm, height: 100mm Speed: 6 rpm Temperature: 1450°C, duration 72 hours Corrosion level increase with lead free crystal glass Corrosion level with Crystal lead free glass with/without BaO are similar Lower corrosion resistance of HZFC compared to AZS material (protective interface layer) in condition of high glass interface removal : this is not the case with horizontal interface like in paving or electrode block due to heavy enriched zirconia interface SAMSUNG CORNING 04/98

Glass evolution impact of refractory stoning potential Tests conditions Temperature: 1450°C Time: 48 hours HZFC AZS HZFC AZS Lead crystals Index HZFC AZS (41% ZrO2) 1-2 Lead free (BaO) Index HZFC AZS (41% ZrO2) 0- 1 Index given from 1 to 5 (1: no stone in drop, 5: lot of crystals in drop)

Lead free Crystal glass HZFC – glass interface Lead Crystal glass Lead free Crystal glass 200µm 200µm No formation of HZFC/Crystal glass interface in each case

Lead free crystal glass AZS – glass interface 200µm Lead Crystal glass 100µm 200µm Lead free crystal glass 100µm 200µm -Dissolution of alumina from eutectic crystals -Free zirconia crystals

Glass defect coming from AZS material in lead free crystal glass Chemical composition of glass defect % 1 2 3 4 Na2O 9.9 10.3 10.4 K2O 3.9 3.8 4.0 MgO 0.05 0.03 0.04 Al2O3 13.4 13.6 13.7 CaO 5.3 4.9 ZnO 0.8 0.7 ZrO2 6.7 6.6 6.4 BaO 5.2 4.8 4.7 TiO2 0.08 SO3  - -

As a conclusion Glass composition change towards lead free glass Enhance corrosion level Doesn’t affect the advantage of using HZFC in terms of defect due to very sharp glass refractory interface New HZFC solution to avoid low temperature oxygen blistering by modifying ZrO2 electrical properties Less glass defects at low temperature (oxygen blisters) Better corrosion resistance without upward drilling phenomenon in join (low temperature area ) Better filling of the block Same advantage as conventional HZFC product