Alloy target, its fabrication, and regeneration processes

• US 6,071,323 A
• Filed: 03/02/1998
• Issued: 06/06/2000
• Est. Priority Date: 03/07/1997
• Status: Expired due to Term

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Kawaguchi, Yukio
• Primary Examiner(s): MAI, NGOCLAN THI
• Application Number:
  US09/033,173
• Time in Patent Office: 827 Days
• Field of Search: 75/245, 75/246, 419/48, 419/33
• US Class Current: 75/246
• CPC Class Codes: C22B 59/00 Obtaining rare earth metals
• CPC Class Codes: C22C 1/0441 Alloys based on intermetallic compounds of the type rare earth - Co, Ni
• CPC Class Codes: C22C 33/0285 with Cr, Co, or Ni having a minimum content higher than 5%
• CPC Class Codes: C22C 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• CPC Class Codes: C23C 14/3414 Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
• CPC Class Codes: G11B 11/10582 Record carriers characterised by the selection of the material or by the structure or form
• CPC Class Codes: G11B 11/10586 characterised by the selection of the material

Abstract

An alloy target comprises at least one rare earth metal element Tb, Dy, Gd, Sm, Nd, Ho, Tm, and Er with a substantial balance of a transition metal element such as Fe, Co and Ni, and has a substantially homogeneous sintered structure and a permeability of 3 or lower. The alloy target is fabricated by a process comprising steps of melting in a high-frequency furnace or crucible furnace, quenching, pulverization, and firing under pressure. After the alloy target has been used up, it is regenerated by mixing alloy powders (to be regenerated) obtained by the mechanical pulverization of the used-up target with the alloy powders obtained at the pulverization step of the aforesaid process to obtain a mixture, and firing the mixture under pressure.

Claims

1. An alloy target used to form a magneto-optical recording layer by a magnetron sputtering technique, which comprises 20 to 30 at % of at least one rare earth metal element selected from the group consisting of terbium, dysprosium, gadolinium, samarium, neodymium, holmium, thulium and erbium with a substantial balance of a transition metal element necessarily including at least one element selected from the group consisting of iron, cobalt and nickel, and has a substantially homogeneous sintered structure in sheet form having a thickness of at least 8 mm and a permeability of up to 3.

2. The alloy target according to claim 1, wherein said transition metal element further includes chromium.

3. The alloy target according to claim 1, which has an oxygen content of up to 1,000 ppm.

4. The alloy target according to claim 1, wherein an Fe₃ Tb type crystal phase accounts for at least 90% of all crystal phases.

5. A process of fabricating an alloy target as recited in claim 1, which comprises steps of:

blending together said rare earth metal element and said transition metal element in such a way that R/(R+T)=20 to 30 at % where R is said rare earth metal element and T is said transition metal element, thereby obtaining a blend,

melting said blend in a high-frequency furnace or crucible furnace to obtain a melt and then quenching said melt to obtain a quenched alloy,

mechanically pulverizing said quenched alloy in a non-oxidizing atmosphere to obtain alloy powders, and

firing under pressure said alloy powders in an inert gas atmosphere or in vacuum, thereby sintering said alloy powders.

6. The process according to claim 5, wherein at least 90% by weight of said alloy powders has a particle diameter of 45 to 425 μ

m.

7. A process of regenerating an alloy target as recited in claim 1 after said alloy target has been used up, which comprises:

a first stage of mechanically pulverizing said used-up alloy target in a non-oxidizing atmosphere to obtain alloy powders to be regenerated,

a second stage comprising steps of blending together said rare earth metal element and said transition metal element to obtain a blend, melting said blend in a high- frequency furnace or crucible furnace to obtain a melt and then quenching said melt to obtain an quenched alloy, and mechanically pulverizing said quenched alloy in a non- oxidizing atmosphere to obtain alloy powders, and

a third stage comprising steps of mixing said alloy powders obtained at said second stage with said alloy powders obtained at said first stage to obtain a mixture and firing under pressure said mixture in an inert gas atmosphere or in vacuum thereby sintering said mixture.

8. The process according to claim 7, wherein R/(R+T) in said blend obtained at said second stage is larger than R/(R+T) in said alloy powders obtained at said first stage by a factor of 1.02 to 1.08, where R is said rare earth metal element and T is said transition metal element.

9. An alloy target as claimed in claim 1, wherein the magneto-optical recording layer has an oxygen content of up to 1,000 ppm.