Grain Boundary Diffusion Patents: Leaders, Trends & White Space 2026
- 30.2% concentration at the top. The top 5 ranked assignees hold 176 of 583 records in scope — a leader well ahead of the field, with the fifth-place holder at 21 records.
- Filings have flattened, not grown. Annual filings rose from 24 in 2017 to a peak of 53 in 2025, but the 2022 midpoint of 51 shows growth stalled years before the peak.
- H01F dominates, but the crossover is real. 63.6% of records sit in H01F (magnets, inductors & transformers), yet 23.2% also touch H01L (semiconductor devices), pointing to diffusion techniques crossing over from chip fabrication.
Filing growth compares 2021 (32 records) with 2024 (38) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 583 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
Grain boundary diffusion is the process of introducing a heavy rare earth element — typically dysprosium or terbium — into the grain boundaries of a sintered RFeB magnet after sintering, rather than alloying it throughout the bulk. The technique raises coercivity while using far less heavy rare earth than bulk alloying, which is why it has drawn sustained patenting activity from magnet makers, materials suppliers and research institutes since the mid-2010s. This landscape covers 583 published records filed between 2015 and the 2026 data cut-off, spanning diffusion source chemistry, adhesion and coating methods, heating profiles, and the resulting magnet microstructure.
Because publication lags filing by roughly 18 months, the most recent filing year in the trend below is understated and should not be read as a real slowdown on its own. Family-level counts, used throughout this page, are the fairer unit for comparing filers because they neutralise continuation filings and multi-jurisdiction duplicates.
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Filing trends and technology composition
Two views of the same 583-record dataset: how filing volume has moved year over year, and how records distribute across IPC subclasses. Because a single record can carry several IPC codes, the class shares below sum to more than 100% of the record total.
A decade of filing activity
Annual filings climbed from 24 in 2017 toward a peak of 53 in 2025, but the 2022 midpoint of 51 shows the growth curve had already gone flat well before the peak — this looks like a maturing field maintaining volume rather than one still accelerating. The 2026 figure of 7 is a partial year and should be read alongside the 18-month publication lag rather than as a drop.
Where the claims sit
H01F (magnets, inductors & transformers) covers 63.6% of the 583 records, confirming this is fundamentally a magnet-materials field. The next-largest classes — H01L at 23.2% and B22F (powder metallurgy) at 17.3% — point to real overlap with semiconductor processing techniques and powder-based fabrication routes, while C23C (coating & surface deposition) at 4.3% and C30B (crystal growth) at 2.6% mark smaller, more specialised pockets of activity.
Shares are the percentage of the 583 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Grain Boundary Diffusion Process for Sintered Magnets with Eureka
This page is one run against one query. Ask Eureka your own question about grain boundary diffusion process for sintered magnets and every answer comes back with the patent numbers behind it.
Try EurekaA representative filing
Method for producing RFeB-based magnet using a Cu-bearing heavy rare earth diffusion alloy
The filing describes preparing a sintered or hot-deformed RFeB-based base material, then adhering a diffusion source alloy containing a heavy rare earth element together with 20-40 mass% copper to its surface, followed by a heating step that drives the heavy rare earth into the grain boundaries. The copper content range is the specific lever the claims turn on: it is presented as controlling how the adhesion substance behaves during heating and, in turn, the resulting diffusion depth and coercivity gain.Filed by Daido Steel, published 2024-11-28.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5242847A | Selective deposition of doped silicon-germanium alloy on semiconductor substrate | 170 |
| 2 | US6791257B1 | Photoelectric conversion functional element and production method thereof | 106 |
| 3 | US4484388A | Method for manufacturing semiconductor Bi-CMOS device | 99 |
| 4 | US5336903A | Selective deposition of doped silicon-germanium alloy on semiconductor substrate, and resulting structures | 55 |
| 5 | US5920774A | Method to fabricate short-channel MOSFETS with an improvement in ESD resistance | 51 |
| 6 | CN101845637A | 钕铁硼磁体晶界扩散工艺 | 47 |
| 7 | JP2012169436A | RH diffusion source and method of producing r-t-b based sintered magnet using the same | 45 |
| 8 | US4290830A | Method of selectively diffusing aluminium into a silicon semiconductor substrate | 42 |
| 9 | US4154632A | Method of diffusing aluminum into silicon substrate for manufacturing semiconductor device | 41 |
| 10 | US4824798A | Method of introducing impurity species into a semiconductor structure from a deposited source | 40 |
Citation counts favour older filings simply because they have had more time to accumulate citations inside the searched corpus — treat them as a signal of influence on the field, not a ranking of current technical importance.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers mean for a filing decision
Three patterns stand out once the ranking, the trend and the IPC composition are read together.
One leader, then a sharp drop-off
The leading assignee holds 57 records against a fifth-place figure of 21 — a gap wide enough that the top 5 combined only reach 30.2% of all 583 records in scope. Below tenth place (11 records, 43.4% cumulative for the top 10), the ranking thins into single- and double-digit filers, meaning most of the field is a long tail rather than a handful of blocking players.
Volume has plateaued, not accelerated
Filings roughly doubled from 24 in 2017 to a 2025 peak of 53, but the 2022 midpoint of 51 was already close to that peak — the field grew early in the window and has since held its level rather than kept climbing. New entrants should expect a stable but not expanding pool of active competitors.
Semiconductor-process techniques are folded in
Nearly a quarter of records carry an H01L (semiconductor devices) classification alongside the expected H01F magnet class, and 17.3% touch B22F powder metallurgy. Diffusion-source deposition and heat-treatment methods appear to be drawing directly on thin-film and powder-processing know-how rather than being magnet-specific inventions from the ground up.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to grain boundary diffusion process for sintered magnets, with the prior art for and against each one.
Who is filing, and where the gaps sit
The ranking spans 100 companies counted in records, from a clear leader down to a long tail of single-digit filers. Co-assignee activity is limited — only 10 pairs recur across the dataset — suggesting most filing happens within single organisations rather than through joint development.
A dominant single filer
The top-ranked assignee holds more than double the fifth-place count of 21, giving it a clear lead in claim density around diffusion source composition and process steps. Its recent-year activity is worth checking directly rather than assumed, since several of the largest filers in this dataset show zero filings in the latest recorded year.
A crowded middle tier
Between fifth place (21 records) and tenth place (11 records), the field narrows quickly, and the top 10 combined reach 43.4% of all 583 records. This mid-tier includes materials suppliers and research institutes alongside established magnet makers, and it is where freedom-to-operate searches typically need the closest attention.
Filing is mostly solo, not joint
Only 10 co-assignee pairs recur in the dataset, and the strongest of them appears in just 6 shared records. Cross-organisation R&D partnerships exist but are the exception rather than the rule in this field, which shifts most of the competitive risk to individual corporate portfolios rather than joint ventures.
| Assignee | Recent year | YoY |
|---|---|---|
| Yantai Dongxing Magnetic Materials Inc. | 0 | — |
| Proterial, Ltd. | 0 | — |
| Toshiba Corporation | 0 | — |
| Hitachi, Ltd. | 0 | — |
| Xiamen Tungsten Co., Ltd. | 0 | — |
| Urban Mining Tech Co., Inc. | 0 | — |
| Fujian Changting Golden Dragon Rare Earth Co., Ltd. | 0 | — |
| Yantai Zhenghai Magnetic Material Co., Ltd. | 0 | — |
Where to take this next
The figures on this page describe where claim space is already dense and where it thins out. Turning that into a filing or freedom-to-operate decision means going deeper into specific claim language and specific competitors.
Check freedom-to-operate before filing
The top 10 ranked assignees hold 43.4% of all 583 records, concentrated around diffusion source composition and heating process claims. A targeted search against those filers' active claims is the first step before committing to a specific diffusion alloy chemistry.
Run a freedom-to-operate search in EurekaTrack the mid-tier for emerging moves
Positions five through ten in the ranking sit close together, and the identity of the most active filer can shift year to year faster than in the top spots. Monitoring this group catches new claim directions before they show up in the aggregate trend.
Set up assignee monitoring in EurekaExplore the under-claimed branches directly
Terbium-free and recycled-feedstock diffusion routes show thinner claim density than the core alloy chemistry. Reviewing the specific claim language in adjacent classes such as C23C and C30B can surface where a first claim is still realistic.
Explore white space in EurekaCommon questions about this landscape
It is a post-sintering treatment in which a heavy rare earth element, usually dysprosium or terbium, is introduced onto the surface of an already-sintered RFeB magnet and driven into the grain boundaries by heating, rather than being alloyed through the whole magnet body. This raises coercivity in the outer regions of the magnet where demagnetisation typically starts, while using substantially less heavy rare earth than bulk alloying. The technique has been the subject of steady patent filing since the mid-2010s, with 583 records in this dataset covering diffusion source chemistry, adhesion and coating methods, and heating profiles.
The ranking in this dataset covers 100 companies counted in records, with a clear leader holding 57 records against a fifth-place figure of 21 — the top 5 combined account for 30.2% of all 583 records in scope. Below the top 10, which together reach 43.4% of records, the field spreads into a long tail of smaller filers including magnet makers, rare earth materials suppliers and research institutes. This is a concentrated-at-the-top field rather than one dominated by a single monopoly holder.
Filing volume grew from 24 records in 2017 to a peak of 53 in 2025, but the 2022 midpoint already stood at 51 — meaning most of the growth happened in the first half of the window and volume has since held roughly flat rather than kept accelerating. The 2026 figure looks low at 7, but that year is only partially captured and publication typically lags actual filing by around 18 months, so it should not be read as a genuine drop-off. Overall the pattern points to a maturing field maintaining a stable filing rate rather than one in early-stage growth.
Terbium-free and reduced-heavy-rare-earth diffusion approaches appear as a narrower slice of this landscape rather than the dominant claim direction, based on the search terms and IPC composition in scope. Given that heavy rare earth supply cost and availability are the commercial reason this process exists at all, diffusion sources that reduce or eliminate terbium and dysprosium content represent one of the more open areas for new claims. Reviewing recent filings specifically in that sub-area, rather than the field as a whole, is the more useful exercise for a team evaluating this route.
H01F (magnets, inductors and transformers) is the anchor class, covering 63.6% of the 583 records in this dataset, but a meaningful share of records also carry H01L (semiconductor devices, 23.2%) and B22F (powder metallurgy, 17.3%), reflecting overlap with thin-film deposition and powder processing techniques used to apply the diffusion source. Smaller but relevant classes include C23C for coating and surface deposition and C30B for crystal growth. A thorough prior art search on this technology should not stop at H01F alone.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.