Material Guide
Alumina Ceramic Grades 95 Percent and 99 Percent Compared
The purity number changes strength, dielectric behaviour and price. Here is what the 99% body actually gives you over 95%, with the measured values from our own material data.
What the Percentage Means
The number is the alumina content of the body. Our 99% body is 99% Al2O3 at 3.85 g/cm3, with zero water absorption and zero gas permeability. The 95% body carries more glassy phase, which lowers cost and lowers dielectric performance.
Mechanical Data on the 99% Body
Rockwell hardness 92 HRA, Vickers 15.7 GPa, flexural strength 330 MPa at 20 degrees C, compressive strength 2000 MPa, fracture toughness 4 MPa m1/2 and modulus of elasticity 350 to 400 GPa.
Thermal Data
Thermal conductivity 27.5 W/m K between 20 and 400 degrees C, thermal expansion coefficient 7.6 x 10-6 per degree C, thermal shock resistance 200 delta T degrees C and a maximum use temperature of 1650 degrees C.
Electrical Data
Dielectric strength above 10 kV/mm, dielectric constant 9.1, dielectric loss angle 0.0002 to 0.0003 at 1 MHz and volume resistivity above 10^14 ohm cm at 20 degrees C.
Which One to Specify
Specify 99% next to electrodes, for vacuum work where gas permeability matters, and where the plate is thin and loaded. Specify 95% for mechanical wear duty where the electrical requirement is modest and cost matters.
Products Covered in This Guide
Al2O3 Alumina Ceramic Parts99% Al2O3 Alumina Ceramic Sheet Blank PlateSingle piece minimum order for wear plates and insulating blanksView specifications
Al2O3 Alumina Ceramic Parts99% 95% Al2O3 Alumina Ceramic RingWear rings and insulating collars machined to your drawingView specifications
Al2O3 Alumina Ceramic PartsAl2O3 Alumina Ceramic SubstratesHeat spreading insulating plates from 0.1 mm thickness with laser scribingView specifications
Al2O3 Alumina Ceramic PartsRefractory Alumina Ceramic TubeWork tubes thermocouple sheaths and element supports to 1650 degrees CView specificationsQuestions About This Topic
Is the 99% body gas tight?
Yes. Both gas permeability and water absorption are zero on the 99% alumina body.
What is the volume resistivity?
Above 10^14 ohm cm at 20 degrees C.
Can I get both grades in the same part?
The ring products are offered in both 99% and 95% alumina. Tell us the duty and we quote the body that fits.
More Guides
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Process GuideHow Ceramic to Metal Metallizing and Brazing WorksBraze alloy does not wet bare ceramic. The joint is made possible by a fired molybdenum manganese layer and a plated finish, and those two layers are where hermetic joints succeed or fail.Apply This to Your Part
Send the drawing and the duty. We will confirm the body and the achievable tolerance before you commit to anything.
Send a 2D or 3D drawing by WhatsApp or email. Samples in 4 to 7 working days.