The ranked leader in this dataset holds 146 records, well ahead of the fifth-place assignee at 40, and the top five combined account for 27.0% of all 1,886 records in scope. That said, the ranking covers 100 companies rather than a small top list, and beyond the leading names filing counts drop off quickly into a long tail of smaller filers. Anyone assessing competitive position should look at both the absolute leader and the shallower gradient among mid-tier filers, since the two groups behave differently.

Filings peaked at 86 in 2017 and had fallen to 21 by 2024, a -74% drop from the 82 filings recorded in 2021. That comparison uses 2024 as the most recent reliable year because publication typically lags filing by around 18 months, so 2025 and 2026 figures are still incomplete and should not be read as confirming a continued decline. On the evidence available, the field has cooled substantially from its 2017 peak rather than being in an active growth phase.

Beyond the core C04B ceramics, cement and refractories class, which covers 35.1% of the 1,886 records, the next largest overlaps are H01M batteries and cells at 11.0%, C01B non-metallic elements and inorganic compounds at 8.5%, and E21B earth and rock drilling at 7.7%. Coating and surface deposition (C23C) and semiconductor devices (H01L) each sit near 5.8-5.9%. Because a single record can carry multiple IPC codes, these figures should be read as independent shares of the total record count, not as parts of a whole.

US5851414A, assigned to Akechi Ceramics and granted in 1998, claims a tundish stopper rod for continuous casting where an engineering-ceramic nut is embedded in the rod body to attach it to a spindle. It is specific to that mechanical assembly and its stated goals of fast correct fitting and heat/mechanical-strength resistance under molten-metal conditions. It does not block ceramic material compositions or firing processes generally; new filings should check specifically against the stopper-rod-and-nut assembly claim rather than assuming broader coverage.

The evidence points to comparatively lighter filing density in branches that sit at the edges of the core C04B classification, such as ceramic coatings applied to battery electrode substrates, surface-layer adhesion on drilled well components, and firing-process optimisation specific to laminated ceramic layers. These branches show real activity — hence their presence in the IPC composition data — but nowhere near the density of the core C04B and C01B classes. That combination of documented interest with lower filing pressure is what makes them worth a closer freedom-to-operate look before committing to a filing strategy there.