Ceramic material powder, method of production thereof, dielectric ceramic composition, electronic device, and multilayer ceramic capacitor

• US 20050260410A1
• Filed: 05/20/2005
• Published: 11/24/2005
• Est. Priority Date: 05/21/2004
• Status: Abandoned Application

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Umeda, Yuji, Fujikawa, Yoshinori, Yamane, Fumikazu
• Application Number:
  US11/133,206
• Publication Number:
  US 20050260410A1
• Time in Patent Office: Days
• US Class Current: 428/403
• CPC Class Codes: B32B 2311/22 Nickel or cobalt
• CPC Class Codes: C01G 23/003 Titanates C01G23/001 takes precedence
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3215 Barium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3239 Vanadium oxides, vanadates or oxide forming salts thereof, e.g. magnesium vanadate
• CPC Class Codes: C04B 2235/3241 Chromium oxides, chromates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3262 Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids, or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint glass constituents C04B2235/36
• CPC Class Codes: C04B 2235/441 Alkoxides, e.g. methoxide, tert-butoxide
• CPC Class Codes: C04B 2235/449 Organic acids, e.g. EDTA, citrate, acetate, oxalate
• CPC Class Codes: C04B 2235/5445 submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/6025 Tape casting, e.g. with a doctor blade
• CPC Class Codes: C04B 2235/6582 Hydrogen containing atmosphere
• CPC Class Codes: C04B 2235/6584 at an oxygen percentage below that of air
• CPC Class Codes: C04B 2235/663 Oxidative annealing
• CPC Class Codes: C04B 2235/72 Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics
• CPC Class Codes: C04B 2235/724 : Halogenide content
• CPC Class Codes: C04B 2235/726 : Sulfur content
• CPC Class Codes: C04B 2235/727 : Phosphorus or phosphorus compound content
• CPC Class Codes: C04B 2237/346 : Titania or titanates
• CPC Class Codes: C04B 2237/405 : Iron metal group, e.g. Co or Ni
• CPC Class Codes: C04B 35/4682 : based on BaTiO3 perovskite phase
• CPC Class Codes: C04B 35/628 : Coating the powders or the macroscopic reinforcing agents
• CPC Class Codes: C04B 35/62807 : Silica or silicates
• CPC Class Codes: C04B 35/6281 : Alkaline earth metal oxides
• CPC Class Codes: C04B 35/62815 : Rare earth metal oxides
• CPC Class Codes: C04B 35/62818 : Refractory metal oxides
• CPC Class Codes: C04B 35/62886 : by wet chemical techniques
• CPC Class Codes: C04B 35/62894 : with more than one coating layer
• CPC Class Codes: C04B 35/62897 : Coatings characterised by their thickness
• CPC Class Codes: C04B 35/64 : Burning or sintering processes C04B33/32 takes precedence ; powder metallurgy B22F
• CPC Class Codes: H01G 4/1227 : based on alkaline earth titanates
• CPC Class Codes: Y10T 428/2991 : Coated

Abstract

A ceramic material powder comprised of main ingredient particles formed by barium titanate having on their surfaces a covering layer comprised of a secondary ingredient additive, wherein when an average radius of the main ingredient particles is “r” and an average radius of the covering layer is “Δr”, the Δr is controlled to a range of 0015r to 0.055r, thereby enabling acquisition of a multilayer ceramic capacitor or other electronic device satisfying both the X7R characteristic prescribed in the EIAJ standard and B characteristic prescribed in the Japan Industrial Standard (JIS), that is, excellent in temperature stability of the electrostatic capacity, having a good insulation resistance value, relative dielectric constant, or other characteristics, and having a long accelerated life of the insulation resistance.

Claims

1. A ceramic material powder comprised of main ingredient particles made of barium titanate having on their surface a covering layer made of a secondary ingredient additive, wherein

when an average radius of said main ingredient particles is “

r” and

an average thickness of said covering layer is “

Δ

r”

, said Δ

r is controlled to a range of 0.015r to 0.055r.

3. The ceramic material powder as set forth in claim 1, wherein said main ingredient particles are comprised of an oxide having a perovskite crystal structure.

4. A dielectric ceramic composition produced using a ceramic material powder as set forth in claim 1, having

a main phase mainly comprised of a main ingredient and

a segregated phase differing from said main phase in composition and crystal structure and including a secondary ingredient in an amount, converted to an oxide, of 10 wt % or more,

an area ratio of said segregated phase at the time of observation of the cross-section of said dielectric ceramic composition being 8% or less of the area of the observation field.

5. An electronic device having a dielectric layer, wherein said dielectric layer is comprised of a dielectric ceramic composition as set forth in claim 4.

6. A multilayer ceramic capacitor having a body comprised of a plurality of internal electrode layers and dielectric layers alternately stacked, wherein said dielectric layers are comprised of a dielectric ceramic composition as set forth in claim 4.

10. A dielectric ceramic composition produced using a ceramic material powder as set forth in claim 3, having

a main phase mainly comprised of a main ingredient and

a segregated phase differing from said main phase in composition and crystal structure and including a secondary ingredient in an amount, converted to an oxide, of 10 wt % or more,

an area ratio of said segregated phase at the time of observation of the cross-section of said dielectric ceramic composition being 8% or less of the area of the observation field.

2. A ceramic material powder comprised of main ingredient particles made of barium titanate having on their surface a covering layer made of a secondary ingredient additive, wherein

when an average radius of said main ingredient particles is “

r” and

an average thickness of said covering layer is “

Δ

r”

, said Δ

r is controlled to a range of r (α

−

β

) to r (α

−

β

) (where the values of α and

β

are constants determined by the composition of the main ingredient particles, the type of the secondary ingredient additive forming the covering layer, etc.)

9. A dielectric ceramic composition produced using a ceramic material powder as set forth in claim 2, having

a main phase mainly comprised of a main ingredient and

a segregated phase differing from said main phase in composition and crystal structure and including a secondary ingredient in an amount, converted to an oxide, of 10 wt % or more,

an area ratio of said segregated phase at the time of observation of the cross-section of said dielectric ceramic composition being 8% or less of the area of the observation field.

7. A method of producing a ceramic material powder comprised of main ingredient particles made of barium titanate having on their surface a covering layer made of a secondary ingredient additive, comprising:

a step of preparing a mixed solution of powder-state main ingredient particles and a solution-state secondary ingredient additive and

a step of heat treating said mixed solution,

a treatment temperature and treatment time of said heat treatment being changed to control an average thickness “

Δ

r”

of said covering layer to a range of 0.015r to 0.055r with respect to an average radius “

r”

of said main ingredient particles.

8. A method of producing a ceramic material powder comprised of main ingredient particles made of barium titanate having on their surface a covering layer made of a secondary ingredient additive, comprising:

a step of preparing a mixed solution of powder-state main ingredient particles and a solution-state secondary ingredient additive and

a step of heat treating said mixed solution,

a treatment temperature and treatment time of said heat treatment being changed to control an average thickness “

Δ

r”

of said covering layer to a range of r (α

−

β

) to r (α

−

β

) with respect to an average radius “

r”

of said main ingredient particles (where the values of α and

β

are constants determined by the composition of the main ingredient particles, the type of the secondary ingredient additive forming the covering layer, etc.).