Chrome Oxide Green in MLCC: The Low-Sodium Grade Behind Reliable Capacitors

A multilayer ceramic Kondensator is a million microscopic sandwiches of Bariumtitanat and nickel. The green powder that helps hold it together never appears on the BOM headline — but its sodium content decides how long the part lives.

Where Cr₂O₃ Fits in the MLCC Recipe

Chromium oxide green has two well-established jobs in MLCC manufacturing. First, as an acceptor Dotierstoff in BaTiO₃-based Dielektrikum ceramics: Cr³⁺ substitutes on the titanium site, compensating oxygen vacancies and suppressing the reduction of Ti⁴⁺ during base-metal-electrode (BME) firing in reducing atmosphere. The result is a Dielektrikum that keeps its Isolationswiderstand and resists DC-bias degradation.

Second, in the glass phase of terminal electrode pastes, where fine Cr₂O₃ tunes the softening point and thermal expansion of the glass so the Abschlusskontakt bonds to the ceramic body without cracking during co-firing.

The Sodium Problem

Sodium is the worst offender because it is small, monovalent and mobile. Under the DC bias a Kondensator sees every second of its life, a sodium ion becomes a moving defect — every hop is Leckstrom, and every hop ages the part.

What the Electronic Grade Spec Looks Like

This is why the DELIKEOXIDE EG-series exists. EG-99 delivers ≥99.2 % Cr₂O₃ with Na₂O ≤100 ppm; EG-99H tightens to ≥99.5 % and ≤50 ppm Na₂O, with iron ≤100 ppm, magnetic impurities ≤5 ppm and a D50 of 0.3–0.8 μm for homogeneous Dotierung in the Bariumtitanat matrix.

Buying Checklist for MLCC Use

• Ask for the sodium number. If the CoA does not state Na₂O, treat it as unspecified.
• Check the iron and magnetic-impurity line. Ferromagnetic particles create insulation defects in thin Dielektrikum layers.
• Specify the D50. Finer grades disperse more uniformly into BaTiO₃; coarser grades save cost where the paste only needs the glass tuning.
• Demand lot consistency. MLCC qualification costs thousands of hours — the raw material must not drift.