Stable Thermistor

• US 20110027587A1
• Filed: 12/19/2008
• Published: 02/03/2011
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Vishay Resistors Belgium BVBA (Vishay Intertechnology Incorporated)
• Original Assignee: Vishay Resistors Belgium BVBA (Vishay Intertechnology Incorporated)
• Inventors: Poulain, Véronique, Schuurman, Sophie, Lannoo, André, Westendorp, Frans F.
• Granted Patent: US 8,362,869 B2
• Time in Patent Office: Days
• US Class Current: 428/402
• 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 2235/3213 Strontium oxides or oxide-forming salts thereof
• 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 2235/3227 Lanthanum oxide or oxide-forming salts thereof
• 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 2235/3275 Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
• CPC Class Codes: C04B 2235/3279 Nickel oxides, nickalates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3281 Copper oxides, cuprates or oxide-forming salts thereof, e.g. CuO or Cu2O
• CPC Class Codes: C04B 2235/76 Crystal structural characteristics, e.g. symmetry
• CPC Class Codes: C04B 2235/768 Perovskite structure ABO3
• CPC Class Codes: C04B 2235/786 Micrometer sized grains, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/80 Phases present in the sintered or melt-cast ceramic products other than the main phase
• CPC Class Codes: C04B 35/016 based on manganites
• CPC Class Codes: C04B 35/42 based on chromites C04B35/047 and C04B35/105 take precedence
• CPC Class Codes: C04B 35/50 based on rare-earth compounds non-oxide rare earth compounds C04B35/5156
• CPC Class Codes: H01C 7/043 Oxides or oxidic compounds
• CPC Class Codes: H01C 7/045 : Perovskites, e.g. titanates
• CPC Class Codes: Y10T 428/2982 : Particulate matter [e.g., sphere, flake, etc.]

Abstract

A thermistor based on a composition having the general formula (I): Re_2-x-yCr_aMn_bM_cE_yO_z wherein Re is a rare earth metal or a mixture of two or more rare earth metals, M is a metal selected from the group consisting of nickel, cobalt, copper, magnesium and mixtures thereof, E is a metal selected from the group consisting of calcium, strontium, barium and mixtures thereof, x is the sum of a+b+c and is a number between 0.1 and 1, and the relative ratio of the molar fractions a, b and c is in an area bounded by points A, B, C and D in a ternary diagram, wherein point A is, if y<0.006, at (Cr=0.00, Mn=0.93+10-y, M=0.07-10-y), and, if y≧0.006, at (Cr=0-00, Mn=0.99, M=0.01), point B is, if y<0.006, at (Cr=0.83, Mn=0.10+10-y, M=0.07−10-y), and, if y≧0.006, at (Cr=0.83, Mn=0.16, M=0.01), point C is at (Cr=0.50, Mn=0.10, M=0.40) and point D is at (Cr=0.00, Mn=0.51, M=0.49), y is a number between 0 and 0.5-x, and z is a number between 2.5 and 3.5.

Claims

1-33. -33. (canceled)

34. A thermistor based on a composition having the general formula (I):

Re_2-x-yCr_aMn_bM_cE_yO_z  

 

(I)

wherein

Re is a rare earth metal or a mixture of two or more rare earth metals,

M is a metal selected from the group consisting of nickel, cobalt, copper, magnesium and mixtures thereof,

E is a metal selected from the group consisting of calcium, strontium, barium and mixtures thereof,

x is the sum of a+b+c and is a number between 0.1 and 1, and

the relative ratio of the molar fractions a, b and c is in an area bounded by points A, B, C and D in a ternary diagram, wherein

point A is, if y<

0.006, at (Cr=0.00, Mn=0.93+10·

y, M=0.07−

10·

y), and,

if y≧

0.006, at (Cr=0.00, Mn=0.99, M=0.01),

point B is, if y<

0.006, at (Cr=0.83, Mn=0.10+10·

y, M=0.07−

10·

y), and,

if y≧

0.006, at (Cr=0.83, Mn=0.16, M=0.01),

point C is at (Cr=0.50, Mn=0.10, M=0.40) and

point D is at (Cr=0.00, Mn=0.51, M=0.49),

y is a number between 0 and 0.5·

x, and

z is a number between 2.5 and 3.5.

35. A thermistor according to claim 34,

wherein

the relative ratio of the molar fractions a, b and c is in an area bounded by points E, F, G, C and H in a ternary diagram, wherein

point E is, if y<

0.006, at (Cr=0.35, Mn=0.58+10·

y, M=0.07−

10·

y), and,

if y≧

0.006, at (Cr=0.35, Mn=0.64, M=0.01),

point F is, if y<

0.006, at (Cr=0.65, Mn=0.28+10·

y, M=0.07−

10·

y), and,

if y≧

0.006, at (Cr=0.65, Mn=0.34, M=0.01),

point G is at (Cr=0.65, Mn=0.10, M=0.25),

point C is at (Cr=0.50, Mn=0.10, M=0.40) and

point H is at (Cr=0.35, Mn=0.22, M=0.43).

36. A thermistor according to claim 34,

wherein

Re is selected from the group consisting of Y, Tb, Dy, Er, La and combinations thereof.

37. A thermistor according to claim 34,

wherein

Re is Y, Dy, Er, La, a mixture of Y and Dy or a mixture of Y and Tb.

38. A thermistor according to claim 34,

wherein

Re is a mixture of Y and Tb, wherein the ratio of the molar fraction of Y to the molar fraction of Tb is between 5:

1 and 1;

1, preferably between 4.5;

1 and 3;

1 and more preferably about 3.5;

1.

39. A thermistor according to claim 34,

wherein

x is a number between 0.2 and 0.6, preferably between 0.3 and 0.5, more preferably between 0.35 and 0.45 and most preferably of 0.4.

40. A thermistor according to claim 34,

wherein

the relative ratio of the molar fractions a, b and c is a=0.4−

0.6;

b=0.23−

0.43;

c=0.08−

0.28.

41. A thermistor according claim 40,

wherein

the relative ratio of the molar fractions a, b and c is a=0.45−

0.55;

b=0.28−

0.38;

c=0.12−

0.22.

42. A thermistor according to claim 41,

wherein

the relative ratio of the molar fractions a, b and c is a=0.5:

b=0.33;

c=0.17.

43. A thermistor according to claim 34,

wherein

M is Ni.

44. A thermistor according to claim 34,

wherein

Re is Y, Dy, Er, La, a mixture of Y and Dy or a mixture of Y and Tb and M is Ni.

45. A thermistor according to claim 34,

wherein

z is a number between 2.75 and 3.25, preferably between 2.90 and 3.10, more preferably between 2.95 and 3.05 and most preferably of 3.00.

46. A thermistor according to claim 34,

wherein

y is a number between 0.01 and 0.2, preferably between 0.02 and 0.1, more preferably between 0.03 and 0.06 and most preferably of 0.05.

47. A thermistor according to claim 46,

wherein

E is calcium.

48. A thermistor according to claim 46,

wherein

c is at least 0.01.

49. A thermistor according to claim 46,

wherein

M is nickel, cobalt or copper.

50. A thermistor according to claim 46,

wherein

Re is Er.

51. A thermistor according to claim 50,

wherein

the composition has the general formula:

Er_iCa_jCr_kMn_lNi_sO_m  

 

(II)

wherein

i is a number between 1.4 and 1.6,

j is a number between 0.02 and 0.2,

k is a number between 0.15 and 0.25, preferably of 0.2,

l is a number between 0.14 and 0.24, preferably of 0.19,

s is at least 0.01 and

m is 3.00.

52. A thermistor according to claim 51,

wherein

the composition has the formula (III):

Er_1.55Ca_0.05Cr_0.2Mn_0.19Ni_0.01O₃  

 

(III).

53. A thermistor according to claim 34,

wherein

y is 0.

54. A thermistor according to claim 53,

wherein

the composition has the general formula (IV):

Re_1.6Cr_0.2Mn_bNi_cO₃  

 

(IV)

wherein Re is Y, Dy, Er, La, a mixture of Y and Dy or a mixture of Y and Tb, b is a number between 0.12 and 0.14 and c is a number between 0.06 and 0.07.

55. A thermistor according to claim 54,

wherein

Re is a mixture of Y and Tb.

56. A thermistor according to claim 54,

wherein

the composition has the general formula (V):

Y_nTb_pCr_0.2Mn_bNi_cO₃  

 

(V)

wherein n is the molar fraction of Y and is a number between 1.2 and 1.3, p is the molar fraction of Tb and is a number between 0.3 and 0.4, b is a number between 0.12 and 0.14 and c is a number between 0.06 and 0.07.

57. A thermistor according to claim 56,

wherein

the composition has the general formula (VI):

Y_1.24Tb_0.36Cr_0.2Mn_0.132Ni_0.068O₃  

 

(VI).

58. A thermistor according to claim 34,

wherein

the composition comprises a corundum phase and a perovskite phase.

59. A thermistor according to claim 58,

wherein

the molar fraction of the corundum phase is between 0.4 and 0.8, preferably between 0.5 and 0.7, and the molar fraction of the perovskite phase is between 0.2 and 0.6, preferably between 0.3 and 0.5 based on the total composition.

60. A thermistor according to claim 59,

wherein

the molar fraction of the corundum phase is 0.6 and the molar fraction of the perovskite phase is 0.4 based on the total composition.

61. A thermistor according to claim 58,

wherein

the average particle size of the composition of the corundum phase is less than 3 μ

m, preferably less than 2 μ

m and more preferably between 1.5 and 1.9 μ

m.

62. A thermistor according to claim 58,

wherein

the average particle size of the composition of the perovskite phase is less than 3 μ

m, preferably less than 2 μ

m and more preferably between 1.0 and 1.9 μ

m.

63. A thermistor according to claim 34,

wherein

the average particle size of the composition with the general formula (I) of the thermistor is less than 3 μ

m, preferably less than 2 μ

m and more preferably between 1.0 and 1.5 μ

m.

64. A thermistor according to claim 34,

wherein

the resistivity of the thermistor at 25°

C. is between 2 and 2.000 kΩ

·

mm, preferably between 500 and 1.500 kΩ

·

mm and more preferably between 1.000 and 1.200 Ω

·

mm.

65. A thermistor according to claim 34,

wherein

the B_25/85 value of the thermistor is between 2,000 and 4,000 K.

66. A method for producing a thermistor which is based on a composition having the general formula (I):

Re_2-x-yCr_aMn_bM_cE_yO_z  

 

(I)

wherein

Re is a rare earth metal or a mixture of two or more rare earth metals,

M is a metal selected from the group consisting of nickel, cobalt, copper, magnesium and mixtures thereof,

E is a metal selected from the group consisting of calcium, strontium, barium and mixtures thereof,

x is the sum of a+b+c and is a number between 0.1 and 1, and

the relative ratio of the molar fractions a, b and c is in an area bounded by points A, B, C and D in a ternary diagram, wherein

point A is, if y<

0.006, at (Cr=0.00, Mn=0.93+10·

y, M=0.07−

10·

y), and,

if y≧

0.006, at (Cr=0.00, Mn=0.99, M=0.01),

point B is, if y<

0.006, at (Cr=0.83, Mn=0.10+10·

y, M=0.07−

10·

y), and,

if y>

0.006, at (Cr=0.83, Mn=0.16, M=0.01),

point C is at (Cr=0.50, Mn=0.10, M=0.40) and

point D is at (Cr=0.00, Mn=0.51, M=0.49),

y is a number between 0 and 0.5·

x, and

z is a number between 2.5 and 3.5, said method comprising the steps of;

i) mixing at least one rare earth metal oxide with manganese oxide and with at least one metal oxide selected from the group consisting of nickel oxide, cobalt oxide, copper oxide and magnesium oxide, and, optionally with at least one compound selected from the group consisting of calcium carbonate, strontium carbonate, barium carbonate and mixtures thereof, and/or, optionally, with chromium oxide,

ii) milling the mixture obtained in step i),

iii) forming the mixture obtained in step ii) into an article having a desired shape and

iv) sintering the article.