Ceramic Slurry Bubbles Eliminated in One Go! Density Measurement

From tape casting, injection molding to spraying, covering slurry defoaming for electronic ceramics, structural ceramics and functional ceramics


Ceramic Slurry is a high solid content suspension system mixed by ball milling or stirring of ceramic powder (alumina, zirconia, silicon carbide, barium titanate, PZT, etc.) and organic carriers (binder, dispersant, plasticizer, solvent). It is widely used in tape casting (MLCC/substrate), slip casting (structural parts), hot die casting (precision parts), ceramic spraying and gel casting processes. Bubbles entrained in ceramic slurry directly cause defects such as pores, uneven density, dielectric layer fracture and bending deformation after sintering. Especially, it greatly affects dielectric properties, breakdown voltage of electronic ceramics and mechanical strength of structural ceramics. Through self-developed planetary mixing and defoaming technology, Sinos provides a complete solution from powder dispersion to vacuum defoaming for all types of ceramic slurries.


◆ Material Properties

Common Ceramic Powders

Al₂O₃、ZrO₂、SiC、BaTiO₃、PZT、AlN、Si₃N₄

Organic Carrier Systems

PVB/MEK tape casting system, PEG/glycerin injection molding system, paraffin hot die casting system, acrylic dispersion system

Solid Content Range

40~65vol% (45~55vol% for tape casting slurry, 35~50vol% for slip casting slurry, 55~65vol% for hot die casting)

Slurry Viscosity Range

50~150,000 cps (50~500cps for tape casting slurry, 1,000~20,000cps for slip casting, 50,000~150,000cps for hot die casting)

Powder Particle Size

D50=0.2~5μm (submicron grade for electronic ceramics) to D50=5~50μm (structural ceramics)

Typical Application Scenarios

Tape casting, slip casting, hot die casting, gel casting, ceramic spraying


◆ Mature Application Fields

📱 MLCC Multilayer Ceramic Capacitors

BaTiO₃ barium titanate tape casting slurry, dielectric layer thickness 1~10μm, slurry viscosity 50~300cps. Bubbles directly affect dielectric layer integrity and breakdown voltage.

🔌 Ceramic Substrates & Packaging

Al₂O₃/AlN alumina or aluminum nitride tape casting slurry, used for IGBT substrates and LED heat dissipation substrates, slurry viscosity 200~800cps, high thermal conductivity and insulation required.

🦷 Zirconia Dental / Medical Ceramics

3Y-TZP zirconia slip casting or gel casting slurry for dental crowns, implants and artificial joints, slurry viscosity 5,000~30,000cps, high density and biocompatibility required.

📡 Piezoelectric Ceramic Components

PZT lead zirconate titanate tape casting or slip casting slurry for ultrasonic transducers, filters and actuators, slurry viscosity 1,000~10,000cps. Bubbles affect polarization uniformity.

🔧 Structural Wear-resistant Ceramic Parts

Al₂O₃/SiC alumina or silicon carbide slip casting slurry for wear-resistant parts such as sealing rings, bearings, liners and nozzles, slurry viscosity 3,000~20,000cps.

🔋 Solid-State Battery Ceramic Electrolytes

LLZO/LLZTO solid electrolyte ceramic slurry for thin-film electrolyte layers by tape casting, slurry viscosity 100~2,000cps. Bubbles cause interruption of ion conduction.

🏭 Industrial Ceramic Coatings

Al₂O₃/ZrO₂ ceramic spraying suspension for thermal barrier coatings and wear-resistant coatings on aero-engine blades, slurry viscosity 500~5,000cps.

🔥 High-Temperature Kiln Furniture & Refractories

Mullite/corundum slip casting slurry for kiln furniture such as shelves, saggers and crucibles, slurry viscosity 5,000~15,000cps, requiring thermal shock resistance and long service life.

🎓 Scientific Research & New Material Development

New ceramic formula development and process parameter verification for universities and research institutes, small-batch slurry preparation and defoaming test, unlimited viscosity range, free sample testing.


◆ Core Problems Caused by Bubbles

⚠️ Porosity & Insufficient Density After Sintering

Bubbles in the slurry leave voids during drying and sintering, reducing sintered body density. Electronic ceramics require relative density ≥97% (≥99% for MLCC). Residual bubbles directly shift dielectric constant and reduce breakdown voltage.

⚠️ Dielectric Layer Fracture & Electrical Performance Failure

For thin-layer devices such as MLCC, a single bubble can cause penetrating micron-scale defects in dielectric layers, resulting in short circuit or insulation failure. Every 0.1% increase of gas content in tape casting slurry may multiply defect rates.

⚠️ Uneven Shrinkage, Warpage & Cracking

Uneven bubble distribution causes inconsistent shrinkage in different regions of green body. Internal stress concentration occurs during drying and sintering, triggering warpage, deformation or even penetrating cracks, making dimensional accuracy unguaranteed.

⚠️ Surface Pinholes & Deteriorated Surface Finish

Burst of surface bubbles forms pinholes and pits, raising surface roughness of cast films and slip cast parts. Subsequent grinding & polishing cost increases, and parts may be scrapped in severe cases.


◆ Recommended Process — Planetary Mixing & Defoaming

Step 1   Powder Pre-Dispersion

Add ceramic powder into organic carrier (binder + solvent + dispersant) in batches. Pre-stir at low speed to wet powder preliminarily and prevent dry powder agglomerates from trapping air.

Step 2   Ball Milling / High-Speed Dispersion

Ball mill or high-speed disperse powder to target D50, and fully mix powder with carrier. A large amount of air is entrained at this stage, significantly raising slurry gas content.

Step 3   Vacuum Mixing & Defoaming

Start planetary stirring under -95KPa vacuum. Revolution + rotation continuously flips slurry to expand, float and burst bubbles. Most entrained gas is removed within 3~8 minutes.

Step 4   Direct Tape Casting / Slip Casting After Defoaming

Discharge directly to tape caster or casting process after vacuum release without container transfer to avoid secondary air entrapment. Fully enclosed operation ensures stable and controllable slurry gas content.


◆ Recommended Equipment

  1. MIX60 — Laboratory planetary mixer defoamer, single processing capacity 5~60g, suitable for electronic ceramic slurry formula development and tape casting parameter verification, supports -95KPa vacuum defoaming.

  2. MIX90 — Pilot-scale mixing defoamer, single processing capacity 200~900g, suitable for batch preparation of medium viscosity ceramic slurry (≤80,000cps), universal model for structural ceramics / piezoelectric ceramics.

  3. MIX1000PLUS — Large-capacity flagship model, max single processing capacity 2000g, specialized for high solid content & high viscosity ceramic slurry (≤200,000cps), suitable for mass production of MLCC / substrate slurry.

  4. MIX2000 — Industrial mass production model, single processing capacity over 2000g, equipped with automatic loading & unloading system to meet the cycle requirement of mass ceramic production.


◆ Test Cases

▶ Case 1: BaTiO₃ Barium Titanate MLCC Tape Casting Slurry

Test Material

BaTiO₃ barium titanate powder (D50=0.3μm) + PVB/MEK tape casting system, solid content 50vol%

Slurry Viscosity

Approx. 150 cps

Test Model

MIX60

Vacuum Degree

-95KPa

Rotation Speed

Revolution 1500rpm / Rotation 1000rpm

Treatment Time

3 min

Treatment Temperature

Room temperature (25℃), sealed and protected from light

✅ Defoaming Result: Cross-section porosity of tape casting slurry ＜0.3%, thickness uniformity of cast film ±1.5%. Relative density after sintering ≥99.2%, breakdown voltage ＞15KV/mm, dielectric loss tanδ＜0.02, meeting the integrity requirements of dielectric layers for high-capacity MLCC.


▶ Case 2: Al₂O₃ Alumina Structural Ceramic Slip Casting Slurry

Test Material

Al₂O₃ alumina powder (D50=8μm) + PEG/glycerin water-based slip casting system, solid content 55vol%

Slurry Viscosity

Approx. 5,000 cps

Test Model

MIX90

Vacuum Degree

-95KPa

Rotation Speed

Revolution 1800rpm / Rotation 1200rpm

Treatment Time

5 min

Treatment Temperature

Room temperature (25℃)

✅ Defoaming Result: Cross-section porosity of slip-cast green body ＜0.5%, no cracking after drying. Relative density after sintering ≥98.5%, flexural strength ≥380MPa, Vickers hardness HV12.5, no surface pinhole defects, meeting requirements for structural parts such as sealing rings and bearings.


▶ Case 3: ZrO₂ Zirconia Dental Ceramic Gel-Casting Slurry

Test Material

3Y-TZP zirconia powder (D50=0.5μm) + acrylamide monomer gel casting system, solid content 58vol%

Slurry Viscosity

Approx. 2,000 cps

Test Model

MIX90

Vacuum Degree

-95KPa

Rotation Speed

Revolution 2000rpm / Rotation 1500rpm

Treatment Time

5 min

Treatment Temperature

Room temperature (25℃), light-shielded operation

✅ Defoaming Result: Cross-section porosity of gel-cast green body ＜0.3%. Relative density after sintering ≥99.5%, flexural strength ＞1000MPa, fracture toughness KIC＞8MPa·m^1/2, good translucency, satisfying mechanical and aesthetic requirements for dental all-ceramic crowns and bridges.


◆ Comparison Before and After Improvement

Comparison Item

Manual Stirring / Atmospheric Mixing

Static Vacuum Defoaming Tank

Sinos Planetary Mixing & Defoaming

Slurry Porosity

3~10%

1~3%

＜0.3%

Relative Density After Sintering

90~95%

95~98%

≥99%

Powder Dispersion Uniformity

Severe agglomeration, uneven distribution

Cannot improve dispersion, only degas

Uniform dispersion without agglomeration

Tape Cast Film Thickness Uniformity

Deviation ±5~10%

Deviation ±3~5%

Deviation ±1.5%

Yield Rate

55~70%

80~90%

＞98%

Processing Time

30~60 min (poor effect)

20~40 min (degas only)

3~8 min (mixing + defoaming)


🎯 Free Sample Test    
          Send us your ceramic slurry samples, we will test defoaming parameters and issue reports.