Ceramic Materials Analysis

Ceramic materials are formed by processing inorganic particles under high pressure and at high temperature in most cases. The surface chemistry of these particles plays a major role in the sintering of particles.  Binding materials that provide a more complete bonding of particles may be added.  Brittle ceramic materials tend to fracture along the interfaces of the original particles sintered together and x-ray photoelectron spectroscopy (XPS) surface analysis can be used to investigate the properties of the materials along this extremely thin fracture surface.  Analysis by EDX will provide a more nearly bulk material analysis.

In some cases, ceramic layers are formed from a paste of inorganic particles in an organic binder, to which heat is applied.  Ceramic materials may be deposited by a sputtering process or by a chemical vapor deposition (CVD) process.  Anderson Materials Evaluation has many ways to characterize these materials for their composition and physical properties.  We have many means to identify problems and to suggest process or materials ingredient changes to our clients.  Some examples follow:

TMA:

  • Measure thermal expansion rates (often called CTE) as a function of temperature
  • Measure shrinkage as a function of firing a green ceramic to 800° C
  • Measure any phase transition temperatures below 800° C

TGA:

  • Measure the change of weight as a function of temperature to determine the rate of binder loss with temperature to 1000ºC
  • Measure outgassing of ceramic upon heating
  • Measure the weight of absorbed water or other fluid due to porosity upon heating to 1000ºC

SEM and Optical Microscopy:

  • Imaging of fracture surfaces to determine particle sizes and see residues of organic binders
  • Cross section analysis to evaluate cracks and voids
  • Examine surfaces for cracks and voids
  • Detect stains to identify their cause with EDX or XPS

Profilometry:

  • Determine surface roughness of cast or machined surfaces

XPS or ESCA Surface Analysis:

  • Measures all elements except hydrogen to depth of 10 nm
  • Argon ion etching allows composition analysis to greater depths
  • Analysis of the composition of ceramic pre-cursor powders or particles
  • Analysis of surface contamination of fired ceramics
  • Check chemistry of binding agents to promote sintering
  • Measure water content, impurities, and reacted layers on raw ceramic material particles
  • Analysis of fracture surface chemistry to determine binder and pre-sintered particle surface chemistry effects on fracture plane
  • Degradation effects upon ceramic such as caused by moisture on boron nitride (BN) or on alumina (Al2O3)
  • Precise quantitative chemical phase identifications
  • Measure changes in ceramic due to environment, such as leaching of elements, chemical uptake in the voids between poorly sintered particles, and reaction products

Energy Dispersive X-ray Analysis (EDX or EDS) :

  • Measures elements sodium and heavier semi-quantitatively
  • Detects elements carbon, nitrogen, oxygen, and fluorine
  • Determine elemental composition to depths of 1 to 2 micrometers

Infrared Spectroscopy (FTIR) Analysis:

  • Check the organic binder chemistry of a ceramic paste
  • Identify organic contaminants on ceramic or absorbed by it after use
  • Identify carbonates, water, phosphates, sulfates, and nitrates in inorganic pre-cursor particles

RGA Mass Spectroscopy:

  • Identify outgassing products such as boric acids from boron nitride BN caused by hydration
  • Identify and measure contaminants picked up while in use or storage

An Investigation of a Cracking & Yellowing Cubic Zirconia Ceramic

Cracking & Yellowing Zirconia Ceramic

A yttrium-stabilized cubic zironia white ceramic used in critical components designed to evade corrosion problems was found to be cracking and yellowing in use.  This bad ceramic part had been supplied to our customer by a company in Asia.  XPS examined the fracture surfaces in the bad and a good ceramic.  Such fracture surfaces present the surfaces of the cubic zirconia particles and the binder materials that aid in sintering them together.  The bad ceramic had higher concentrations of nitrogen, aluminum, and zinc in the fracture surfaces than the good material did.  The well-behaved ceramic material had more silicon in the fracture surfaces.  In use, the sodium found on both good and bad fracture surfaces was leached from the bad material interparticle interfaces and the carbon concentration increased to cause yellowed ceramic.  The bad ceramic was either more easily leached in use or the micro-voids between ceramic particles were larger or more interconnected compared to the good ceramic material.