Dielectric ceramic composition and multilayer ceramic capacitor made of said dielectric ceramic composition

Abstract

The present invention relates to a multilayer ceramic capacitor made by alternately stacking ceramic dielectric layers and inner electrodes containing mainly base metals, x Na y Li z A 1-x-y-z ) m (Nb u Ta v B w )O3, a major component having a perovskite structure ABO3, where A is one element selected from Ca, Sr, and Ba, B is one element selected from Ti, Zr, Hf, and Sn, x, y, z, u, v, and w are the mole fractions of each element, and m is the molar ratio of the A-site element to the B-site element, within the following ranges: 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, ...y≦0.90, 0.00≦z≦0.12, 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0.95≦m≦1.05, 0.05≦y≦0.90, 0.00≦z≦0.12, 0.95≦m≦1.05, 0.05≦x

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to pending U.S. Provisional Application No. 63 / 142,766, filed January 28, 2021, the contents of which are incorporated herein by reference.

[0002] The present invention relates to a dielectric ceramic composition and a multilayer ceramic capacitor containing the dielectric ceramic composition. The dielectric ceramic composition of the present disclosure is capable of being co-fired with base metal internal electrodes in a reducing atmosphere. The multilayer ceramic capacitor produced is advantageously used in high temperature applications. [Background technology]

[0003] With the rapid development and popularization of information and electronic technology in the past two decades, the multilayer ceramic capacitor industry has flourished due to the increasing demand for electrical energy storage devices in numerous applications, such as portable electronic devices, personal computers, mobile phones, televisions, etc. In these cases, barium titanate BaTiO3 has been overwhelmingly used as the essential ceramic dielectric material due to its high dielectric constant, dielectric loss, and stable capacitance variation over the temperature range of -55°C to 125°C. However, as a ferroelectric material, BaTiO3 is well known to undergo the well-known Curie transition at about 125°C, resulting in a significant drop in dielectric constant along with a steep drop in the temperature coefficient of capacitance. Nowadays, the emergence of new electronic technology applications in extreme environments, such as engine control units, downhole drilling exploration, and pulsed power electronics, requires the maintenance of stable capacitance in the highest operating temperature window of 175°C to 200°C or even higher. Extensive research efforts have been made to stabilize the temperature-capacitance characteristics of BaTiO3-based capacitors through extensive doping modification packages, but the extended operating temperature is still limited to 150°C. However, considerable attention has been paid to developing new dielectric materials that allow for application in harsh environments at temperatures between 175°C and 200°C or even higher. Among various candidates, alkali niobate-based ceramics have proven feasible for the development of high-temperature capacitors due to their high Curie transition temperatures. For example, such a Curie transition occurs at 1000 K (K 0.5 Na 0.5 ) occurs at about 410 °C in NbO3 ceramics. Detailed firing studies and defect chemistry investigations demonstrate that alkaline niobate ceramics (1) can be co-fired with nonmetals such as Cu and Ni in reducing atmospheres due to well-tuned chemical thermodynamics that reduce the volatility of the alkaline elements, and (2) can be used to create multilayer electronic devices with base metal internal electrodes. For example, in U.S. Pat. No. 9,564,271 and WO2018 / 062084A1, multilayer ceramic capacitors with Ni internal electrodes are formed using (K,Na)NbO3-based and NaNbO3-based dielectric ceramic compositions.

[0004] Despite considerable efforts, there remains a need for improved ceramic dielectrics, especially those suitable for use at high voltages and temperatures, and especially those suitable for use in multilayer ceramic capacitors. Summary of the Invention [Problem to be solved by the invention]

[0005] Provided herein are dielectric ceramics that are particularly suitable for use at high temperatures.

[0006] Also provided herein is a multilayer ceramic capacitor comprising a dielectric ceramic, the capacitor being suitable for use at high temperatures. [Means for solving the problem]

[0007] These and other advantages, as will be appreciated, are achieved by providing a dielectric ceramic composition comprising: (K x Na y Li z A 1-x-y-z ) m (Nb u Ta v B w )O3 The main component is defined by the formula A is at least one element selected from the group consisting of Ca, Sr, and Ba; B is at least one element selected from the group consisting of Ti, Zr, Hf, and Sn; x, y, z, u, v, and w are the mole fractions of each element; m is the molar ratio of A-site and B-site elements, 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0 <u<1、 0.0≦w≦0.3, and A principal component where u+v+w=1, A first sub-material including at least one rare earth element selected from the group consisting of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Yu; a second secondary material comprising at least one transition metal element selected from the group consisting of V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn; and a third minor material comprising a frit.

[0008] Yet another embodiment is a multilayer ceramic capacitor comprising: A plurality of dielectric ceramic layers, each of said layers comprising: (K x Na y Li z A 1-x-y-z ) m (Nb u Ta v B w )O3 A dielectric composition defined by the formula: A is at least one element selected from the group consisting of Ca, Sr, and Ba; B is at least one element selected from the group consisting of Ti, Zr, Hf, and Sn; x, y, z, u, v, and w are the mole fractions of each element; m is the molar ratio of A-site and B-site elements, 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0 <u<1、 0.0≦w≦0.3, and a dielectric composition in which u+v+w=1; a first sub-material comprising at least one rare earth element selected from the group consisting of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Yu; A second secondary material comprising at least one transition metal element selected from the group consisting of V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn; and a dielectric ceramic layer having a third minor material comprising a frit; A plurality of internal electrodes including a base metal such as Ni, Cu, or an alloy thereof; and a pair of external electrodes formed on each end of the capacitor element body.

[0009] Yet another embodiment is a method of forming a multilayer ceramic capacitor, comprising the steps of: forming a dielectric ceramic precursor; forming a stack of alternating layers of a dielectric ceramic precursor and layers of a metal; The laminate is compressed and the dielectric precursor is sintered. (K x Na y Li z A 1-x-y-z ) m (Nb u Ta v B w )O3 The main component is defined by the formula A is at least one element selected from the group consisting of Ca, Sr, and Ba; B is at least one element selected from the group consisting of Ti, Zr, Hf, and Sn; x, y, z, u, v, and w are the mole fractions of each element; m is the molar ratio of A-site and B-site elements, 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0 <u<1、 0.0≦w≦0.3, and Principal component where u+v+w=1, a first sub-material comprising at least one rare earth element selected from the group consisting of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Yu; A second secondary material comprising at least one transition metal element selected from the group consisting of V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn; and and forming a dielectric ceramic layer having a dielectric composition defined by a third minor material comprising a frit. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a cross section of a multilayer ceramic capacitor using a dielectric ceramic composition according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention is specialized in alkaline niobate-based dielectric ceramic compositions with additional doping packages of transition metals and rare earth elements. It is generally known that doping or co-doping with transition metal elements and / or rare earth elements is favorable for fine-tuning the defect chemistry of electro-ceramic materials from the standpoint of microstructure, and thus manipulating micro-electrical properties such as insulation resistance and long-term reliability. The dielectric ceramic devices can be co-fired with inexpensive electrodes that mainly contain base metals at low oxygen partial pressure, thus making it possible to create multilayer ceramic capacitors that can be applied at high temperatures.

[0012] The present invention is specialized in a dielectric ceramic composition that can provide excellent temperature-capacitance characteristics from low to high temperatures. Specifically, a capacitor made of the dielectric ceramic composition of the present disclosure can have a capacitance temperature coefficient within ±50% over a temperature range of -55°C to 200°C, more preferably within ±20% over a temperature range of -55°C to 200°C, relative to the capacitance at 25°C.

[0013] The dielectric ceramic composition has a dielectric constant of at least 300 at 25° C., and more preferably a dielectric constant of at least 1000 to 2000.

[0014] The present invention also specializes in dielectric ceramic compositions that are amenable to co-firing with inner electrodes using inexpensive base metals such as Ni in a reducing atmosphere.

[0015] The present invention also relates to a multilayer ceramic capacitor formed in a pattern in which a plurality of laminated ceramic layers and a plurality of inner electrode layers are alternately laminated. The ceramic layers are made of the dielectric ceramic composition of the present invention, and the inner electrode layers are made of a conductive paste mainly containing a base metal such as Ni. The resulting multilayer ceramic capacitor can have a temperature coefficient of capacitance of ±15% over a temperature range of -55°C to 200°C after co-firing at a low oxygen partial pressure.

[0016] The above objectives are: (K x Na y Li z A 1-x-y-z ) m (Nb u Ta v B w )O3 A perovskite structure of the formula ABO3, wherein A is at least one element selected from the group consisting of Ca, Sr, and Ba; B is at least one element selected from the group consisting of Ti, Zr, Hf, and Sn; x, y, z, u, v, and w are the mole fractions of each element; m is the molar ratio of A-site and B-site elements, 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0 <u<1、 0.0≦w≦0.3, and This is achieved in a multilayer ceramic capacitor device having a dielectric ceramic composition having a main component with the perovskite structure ABO3 formula, where u+v+w=1.

[0017] The ceramic composition further includes a first minor material including at least one element selected from rare earth compounds, the rare earth element being 10 molar parts or less relative to 100 molar parts of the main component.

[0018] The ceramic composition further includes a second sub-material containing at least one element selected from transition metals, and the transition metal element is in the range of 0.05 to 10.00 parts by mole relative to 100 parts by mole of the main component.

[0019] The ceramic composition further comprises a third minor material, also referred to as a frit, comprising a compound with a low melting temperature to aid in the ceramic sintering process, in the range of 0.01 to 15.00 molar parts per 100 molar parts of the main component.

[0020] To obtain the disclosed dielectric ceramic composition, (1) a precursor is first prepared by calcination. Here, a precursor is defined as an intermediate compound or group of compounds made from a specific raw ceramic powder, and although the precursor may contain a whole or partial component of the final composition, the final form of the material is not obtained until the precursor is further mixed with other reactants and treated under specific thermal conditions to achieve the desired chemical reaction. (2) Then, a mixture of the obtained precursor and other dopants such as transition metal compounds, rare earth compounds, and frits is further prepared in the form of a paste with the aid of various organic compounds prior to sintering. (3) Finally, the composition containing the obtained paste mixture forms the dielectric ceramic material disclosed in the present invention upon sintering process. An example is listed in Table 1. The precursors are mainly composed of (K 0.5 Na 0.5)NbO3-BaZrO3, which is prepared by calcination of pre-reacted oxides and carbonates such as K2CO3, Na2CO3, BaCO3, Nb2O5, and ZrO2. The inorganic dopants used to form the paste prior to sintering are MnCO3, Nd2O3, and SiO2.

[0021] [Table 1]

[0022] The dielectric ceramic material may also be obtained by other routes starting with more than one precursor, as exemplified in Table 2, using the same starting raw materials as in Table 1. In this case, the two precursors are Precursor 1 (K 0.5 Na 0.5 )NbO3, and precursor 2 contains mainly BaZrO3, which are prepared separately by calcination. Then, together with the organic compounds, (K 0.5 Na 0.5 ) A paste is formed with a blend of NbO3, BaZrO3, MnCO3, Nd2O3, and SiO2. After sintering, the formulation of Table 2 results in a dielectric material composition that is nearly identical to that produced by the formulation of Table 1.

[0023] [Table 2]

[0024] The present invention will be more fully described in the following examples, which are intended to illustrate, but are not limited to, the scope of the invention, and are indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

[0025] The dielectric ceramic composition of the present invention includes a main component together with an auxiliary material, and the main component is (K x Na y Li z A 1-x-y-z ) m (Nb u Ta v Bw )O3...(1) A perovskite structure represented by the formula ABO3, A is at least one element selected from the group consisting of Ca, Sr, and Ba; B is at least one element selected from the group consisting of Ti, Zr, Hf, and Sn; x, y, z, u, v, and w are the mole fractions of each element; The perovskite structure has the formula ABO3, where m is the molar ratio of the A-site and B-site elements. These subscripts are within the following respective ranges: 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0 <u<1、 0.0≦w≦0.3, and u+v+w=1.

[0026] The ceramic composition further comprises a first submaterial comprising at least one compound containing the rare earth elements: Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Yu. The amount of rare earth element is 10 molar parts or less based on 100 molar parts of the main component. The molar ratio values ​​are: YO 3 / 2 , ScO 3 / 2 , LaO 3 / 2 , CeO2, PrO 11 / 6 , NdO 3 / 2 , SmO 3 / 2 , EuO 3 / 2 , GdO 3 / 2 , TbO 7 / 4 , DyO 3 / 2 , HoO 3 / 2 , ErO 3 / 2 , TmO 3 / 2 , YbO 3 / 2 and LuO 3 / 2 It is calculated based on:

[0027] The ceramic composition further comprises a second sub-material including at least one compound containing the transition metal elements: V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn, and such compound preferably contains at least one of V, Mo, W, Cr, and Mn. The amount of rare earth element is within the range of 0.05 to 10.00 parts by mole per 100 parts by mole of the main component.

[0028] The ceramic composition further comprises a third minor material, also referred to as a frit, which comprises a compound with a low melting temperature to aid in the ceramic sintering process, at least one frit being selected from the group consisting of fluorides such as LiF, NaF, KF, and MgF2, Si, SiO2, and (Ba x Sr y Ca 1-x-y )SiO3 (0≦x, y≦1) and other silicates, BWO3 and other borides, Li2O, MoO3, V2O5 and other oxides, etc. The content of the frit is within the range of 0.01 to 15.00 parts by mole relative to 100 parts by mole of the main component.

[0029] To obtain the dielectric ceramic composition of the present disclosure in the ceramic layer 2 of the multilayer ceramic capacitor 1 shown in FIG. 1, K2CO3, Na2CO3, Li2CO3, BaCO3, SrCO3, CaCO3, Ta2O5, Nb2O5, TiO2, ZrO2, HfO2, transition metal oxides, rare earth oxides, and frits are prepared as starting ceramic raw materials. Furthermore, the raw material compounds containing each component in the dielectric formulation of the present disclosure can be used not only in the form of oxides and carbonates, but also in the form of hydroxides. Specifically, the raw materials are not limited to any form. For example, transition metal elements such as Mn can be added in the form of MnO, MnO2, MnCO3, etc., but this also applies to all other raw materials. The raw materials as the main components are weighed to meet the composition formulation of the present disclosure, and then wet mixed together in a suitable solvent such as water, ethanol, isopropanol, toluene, ethyl acetate, propyl acetate, butyl acetate, mineral spirits, or other suitable hydrocarbon liquids, or a blend thereof, via ball milling with yttrium-stabilized zirconium media. In this way, a pre-sintered ceramic material is obtained after drying and calcination.

[0030] The calcined powders disclosed herein may be further wet milled with the addition of water and / or other suitable organic additives, such as binders, dispersants, solvents, plasticizers, etc., to form a ceramic slip. The selection of organic additives or organic content used herein is not particularly limited.

[0031] To obtain the ceramic slips and ceramic compositions of the present disclosure thereafter, the preparation steps are not limited to the above-mentioned procedures, but may be in such a way that the precursor materials are first calcined and then mixed with the precursors or dopants contain other components of the desired composition to form a ceramic slip with suitable organic additives prior to sintering.

[0032] Examples 1 to 4 are given as examples, but these examples do not limit the scope of the present invention, and modifications obvious to those skilled in the art are included within the scope of the present invention.

[0033] Example 1 K2CO3, Na2CO3, Li2CO3, BaCO3, CaCO3, Ta2O5, Nb2O5, and ZrO2 are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.1mol% to 10.1mol% Li from Li2CO3, 0.5mol% to 12.5mol% Ba from BaCO3, 0.1mol% to 13.6mol% Ca from CaCO3, 0.05mol%~27.70mol% Ta from Ta2O5, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 23.1mol% Zr from ZrO2; the mixture of transition metal oxide, rare earth oxide, and frit comprising: 0.1mol% to 5.0mol% Mn from MnO3, PrO 11 0.2 mol% to 4.9 mol% Pr from 0.01mol%~5.30mol% frit from SiO2 is added as a dopant along with suitable organic additives to form a ceramic slip.

[0034] Example 2 K2CO3, Na2CO3, Li2CO3, BaCO3, SrCO3, CaCO3, Ta2O5, Nb2O5, ZrO2, and transition metal oxides such as MnO and WO3 are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.1mol% to 10.1mol% Li from Li2CO3, 0.5mol% to 12.5mol% Ba from BaCO3, 0.3 mol% to 11.1 mol% Sr from SrCO3, 0.1mol% to 13.6mol% Ca from CaCO3, 0.05mol%~27.70mol% Ta from Ta2O5, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 23.1mol% Zr from ZrO2; 0.1 mol% to 4.9 mol% Mn from MnO; 0.1mol% to 2.2mol% W from WO3 the mixture of rare earth oxide and frit comprising 0.2mol% to 4.9mol% Y from Y2O3, 0.01mol%~5.30mol% frit from CaSiO3 is added as a dopant along with suitable organic additives to form a ceramic slip.

[0035] Example 3 Rare earth oxides such as K2CO3, Na2CO3, BaCO3, SrCO3, CaCO3, Nb2O5, ZrO2, and Y2O3 are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.5mol% to 12.5mol% Ba from BaCO3, 0.3 mol% to 11.1 mol% Sr from SrCO3, 0.1mol% to 13.6mol% Ca from CaCO3, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 23.1mol% Zr from ZrO2; 0.2mol%~4.9mol% Y from Y2O3 the mixture of transition metal oxide and frit comprising 0.1 mol% to 5.0 mol% Mn from MnO2, 0.01mol% to 5.30mol% frit from B2O3 is added as a dopant along with suitable organic additives to form a ceramic slip.

[0036] Example 4 Rare earth oxides such as K2CO3, Na2CO3, BaCO3, SrCO3, CaCO3, Ta2O5, Nb2O5, TiO2, ZrO2, and Nd2O3, and transition metal oxides such as MnO are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials include: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.5mol% to 12.5mol% Ba from BaCO3, 0.3 mol% to 11.1 mol% Sr from SrCO3, 0.1mol% to 13.6mol% Ca from CaCO3, 0.05mol%~27.70mol% Ta from Ta2O5, 70.2mol%~95.5mol% Nb from Nb2O5, 0.05 mol% to 4.70 mol% Ti from TiO2; 0.1mol% to 23.1mol% Zr from ZrO2; 0.2mol% to 4.9mol% La from Nd2O3, 0.1 mol% to 4.9 mol% Mn from MnO; Including, A frit of 0.01 mol % to 5.30 mol % LiF is added as a dopant along with suitable organic additives to form a ceramic slip.

[0037] Moreover, to obtain the desired dielectric composition disclosed in the present invention, dopants such as transition metal compounds, rare earth compounds, and frits can also be added in two separate steps. This means that a portion of transition metal compounds, rare earth compounds, and / or frits is first added into the raw material to prepare a precursor after firing at 700°C-1200°C, which is step 1, and then the remaining amount of transition metal compounds, rare earth compounds, and / or frits is further added to the precursor with suitable organic additives to form a ceramic slip, which is referred to as step 2. The transition metal compounds added in step 1 and step 2 can be the same compound containing the same target transition metal element, or different compounds containing different target transition metal elements. This also applies when the rare earth compounds and frits are added separately in step 1 and step 2. The total amount of transition metal elements, rare earth elements, and frits added in step 1 and step 2 satisfies the value range specified in formula (1).

[0038] Examples 5 to 10 are given by way of illustration, but these examples are not intended to limit the scope of the present invention, which includes modifications obvious to those skilled in the art.

[0039] Example 5 K2CO3, Na2CO3, BaCO3, SrCO3, CaCO3, Nb2O5, ZrO 2、 Transition metal oxides such as HfO2 and MoO3 are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.5mol% to 12.5mol% Ba from BaCO3, 0.3 mol% to 11.1 mol% Sr from SrCO3, 0.1mol% to 13.6mol% Ca from CaCO3, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 19.7mol% Zr from ZrO2; 0.1mol% to 5.4mol% Hf from HfO2, 0.1mol% to 2.2mol% Mo from MoO3; Including, 0.1 mol% to 5.0 mol% Mn from MnO2, 0.2mol% to 4.9mol% Dy from Dy2O3, Frits from LiF from 0.01 mol% to 5.30 mol% A mixture of transition metal oxides, rare earth oxides, and frits consisting of the above may be further added as dopants along with suitable organic additives to form a ceramic slip.

[0040] Example 6 K2CO3, Na2CO3, SrCO3, CaCO3, Ta2O5, Nb2O5, ZrO 2、 HfO 2、 and rare earth oxides such as Yb2O3 are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.3mol% to 13.2mol% Sr from SrCO3; 0.1mol% to 13.6mol% Ca from CaCO3, 0.05mol%~27.70mol% Ta from Ta2O5, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 19.7mol% Zr from ZrO2; 0.1mol% to 5.4mol% Hf from HfO2, 0.2mol%~1.8mol% Y from Yb2O3 the mixture of transition metal oxide, rare earth oxide, and frit comprising: 0.2mol% to 5.0mol% Ce from CeO2, 0.1mol% to 4.9mol% Mn from MnO2, 0.01mol%~5.30mol% frit from CaSiO3 may be further added as a dopant along with suitable organic additives to form a ceramic slip.

[0041] Example 7 K2CO3, Na2CO3, BaCO3, SrCO3, Nb2O5, ZrO 2、 and transition metal oxides such as MnO2 are mixed as starting ceramic raw materials to prepare a precursor after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.5mol% to 12.5mol% Ba from BaCO3, 0.3 mol% to 11.1 mol% Sr from SrCO3, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 19.7mol% Zr from ZrO2; 0.1mol% to 1.6mol% Mn from MnO2 Including, 0.1mol% to 2.2mol% Mn from MoO3; 0.2mol% to 4.9mol% Y from Y2O3, 0.01mol% to 5.30mol% frit from KF A mixture of rare earth oxides, transition metal oxides, and frits including, are further added as dopants along with suitable organic additives to form a ceramic slip.

[0042] Example 8 Transition metal oxides such as K2CO3, Na2CO3, Li2CO3, SrCO3, CaCO3, Ta2O5, Nb2O5, ZrO2, and WO3, and frits such as SiO2 are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.1mol% to 10.1mol% Li from Li2CO3, 0.3 mol% to 11.1 mol% Sr from SrCO3, 0.1mol% to 13.6mol% Ca from CaCO3, 0.05mol%~27.70mol% Ta from Ta2O5, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 23.1mol% Zr from ZrO2; 0.1 mol% to 2.2 mol% W from WO3, 0.01mol%~2.20mol% frit from SiO2 Including, 0.1 mol% to 5.0 mol% Mn from MnO2, 0.2mol% to 4.9mol% Y from Y2O3, 0.01mol% to 5.30mol% frit from BaSiO3 A mixture of rare earth oxides, transition metal oxides, and frits including, are further added as dopants along with suitable organic additives to form a ceramic slip.

[0043] Example 9 Transition metal oxides such as K2CO3, Na2CO3, BaCO3, CaCO3, Nb2O5, ZrO2, and MoO3, rare earth oxides such as Y2O3, and frits such as SiO2 are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.5mol% to 12.5mol% Ba from BaCO3, 0.1mol% to 13.6mol% Ca from CaCO3, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 19.7mol% Zr from ZrO2; 0.1mol% to 2.2mol% Mo from MoO3; 0.1mol%~1.5mol% Y from Y2O3, 0.01mol%~2.20mol% frit from SiO2 Including, 0.1 mol% to 5.0 mol% Mn from MnO2, 0.2mol% to 4.9mol% Y from Y2O3, 0.01mol%~5.30mol% from CaSiO3 A mixture of transition metal oxides, rare earth oxides, and frits including, are further added as dopants along with suitable organic additives to form a ceramic slip.

[0044] Example 10 Frits such as K2CO3, Na2CO3, BaCO3, SrCO3, CaCO3, Ta2O5, Nb2O5, ZrO2, HfO2, and SiO2 are mixed as starting ceramic raw materials to prepare precursors after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.5mol% to 12.5mol% Ba from BaCO3, 0.3 mol% to 11.0 mol% Sr from SrCO3; 0.1mol% to 13.6mol% Ca from CaCO3, 0.05mol%~27.70mol% Ta from Ta2O5, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 19.7mol% Zr from ZrO2; 0.1mol% to 5.4mol% Hf from HfO2, 0.01mol%~2.20mol% frit from SiO2 Including, 0.1 mol% to 5.0 mol% Mn from MnO2, 0.1 mol% to 3.4 mol% V from V2O5, PrO 11 0.2 mol% to 4.9 mol% Pr from Frits from LiF from 0.01 mol% to 5.30 mol% A mixture of transition metal oxides, rare earth oxides, and frits including, are further added as dopants along with suitable organic additives to form a ceramic slip.

[0045] Example 11 K2CO3, Na2CO3, SrCO3, Nb2O5, and ZrO2 are mixed as starting ceramic raw materials to prepare the precursor after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.1mol% to 15mol% Sr from SrCO3, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 23.1mol% Zr from ZrO2; the mixture of transition metal oxide, rare earth oxide, and frit comprising: 0.1 mol% to 5.0 mol% Mn from MnCO3, 0.2mol% to 4.9mol% Eu from Eu2O3, 0.1mol%~25.3mol% frit from SiO2 is added to the main component as a dopant.

[0046] Example 12 - Comparative Example K2CO3, Na2CO3, SrcO3, Nb2O5, and ZrO2 are mixed as starting ceramic raw materials to prepare the precursor after calcination at 700°C to 1200°C. The starting ceramic materials are: 30.7mol% to 70.4mol% K from K2CO3, 29.5mol% to 69.8mol% Na from Na2CO3, 0.1mol% to 11.7mol% Sr from SrCO3, 70.2mol%~95.5mol% Nb from Nb2O5, 0.1mol% to 13.5mol% Zr from ZrO2; the mixture of transition metal oxide, rare earth oxide, and frit comprising: 0.1 mol% to 5.0 mol% Mn from MnCO3, 0.1mol% to 4.2mol% Ca from CaCO3, 0.2mol% to 2.5mol% W from WO3; 0.01mol%~3.3mol% frit from SiO2 is added to the main component as a dopant.

[0047] Preparation of dielectric ceramic disc samples The ceramic powder of the main component and the subcomponent were weighed in the ratio described in the examples, and wet blended in a ball mill for 12 to 30 hours. The blend was then dried at 150°C for 1 to 8 hours. A binder solution was added to the mixture in a mortar, and then formed into granules. The resulting granules were then placed in a steel mold with a diameter of 13 mm, and press-molded at a pressure of 200 MPa to produce a disk compact. The resulting compact was baked in air at 375°C for 10 to 100 hours to burn out the organic binder. Next, combustion was performed in a reducing atmosphere to obtain a sintered disk. This combustion was performed at a peak temperature of 900 to 1350°C for a holding time of 1 to 6 hours. Silver electrodes were then applied to two surfaces of the sintered body to obtain a disk ceramic capacitor corresponding to Example 11 and Example 12.

[0048] Preparation of MLCC samples Sintering at temperatures ranging from 900 to 1350 °C resulted in sintered MLCC chips with a typical size of 3.2 mm x 1.6 mm and nickel inner electrodes. The sintered MLCC chips contained 19 active dielectric ceramic layers and 20 nickel electrodes. The average thickness of the dielectric ceramic layers was determined to be about 12 μm.

[0049] Electrical Measurements The capacitance and dielectric loss of each composition were measured at a temperature range of -55°C to 200°C under the conditions of 1kHz and AC1V. The temperature coefficient of capacitance (TCC) was calculated based on the following formula: TCC(%)=[(C T -C 25 ) / C 25 ] x 100 where T is the temperature at which the measurement was performed and C T and C 25 are the capacitances at temperature T and 25° C., respectively.

[0050] The dielectric constant properties of the disk samples with and without rare earth additions are shown in Table 3.

[0051] [Table 3]

[0052] The results presented in Table 3 show the effect of Example 11 of the present invention containing the rare earth element Eu versus Comparative Example 12. Despite both examples providing TCC within ±20%, the Comparative Example does not achieve sufficient dielectric constant.

[0053] The dielectric constant as a function of firing temperature for disk samples made with the formulation of Example 11 is provided in Table 4.

[0054] [Table 4]

[0055] The results in Table 4 demonstrate that a wide range of dielectric constants can be obtained by varying the firing temperature.

[0056] The dielectric constant properties of MLCC samples made with the formulations shown in Examples 11 and 12 are shown with the data presented in Table 5.

[0057] [Table 5]

[0058] The results presented in Table 5 show that the addition of rare earths can significantly improve the dielectric constant and narrow the TCC range.

[0059] A tape casting process is further used to form the ceramic green sheets by spreading the slip onto the ceramic film using a doctor blade method. After a suitable drying process, the internal electrodes 3a and 3b as shown in Figure 1 are screen printed onto the ceramic green sheets using a conductive ink that contains primarily a base metal such as Ni, Cu, or alloys thereof. It is preferred to use Ni or an alloy that is primarily Ni.

[0060] The resultant is further processed into green chips through a lamination process. A number of ceramic green sheets without printed electrodes thereon are laminated as a bottom cover layer 4b, then a number of ceramic green sheets with printed electrodes thereon are laminated in alternating directions to form AC electrodes 3a and 3b terminating at both ends, and finally a certain number of ceramic green sheets without printed electrodes are laminated as a top cover layer 4a. The laminate is then pressed between 20°C and 120°C to improve the adhesion of all the laminates, and further cut into individual green chips.

[0061] The green chips are heated to 200°C to 700°C in ambient air or a slightly reducing atmosphere for 0.1 to 100 hours to burn out the binder, and then cooled to 30°C for 10 minutes. -4 atm~10 -16 The powder is sintered at temperatures between 900°C and 1350°C in a reducing atmosphere with a partial oxygen pressure of 10 atm. -3 atm~10 -14 The chip may further be subjected to a re-oxidation step by heating to a temperature up to 1100° C. with an oxygen partial pressure between 1 atm.

[0062] The sintered chip is subjected to a corner rounding process by barrel or sandblasting to expose the internal electrodes formed on both end faces of the ceramic sintered body. Then, the external electrodes 5a and 5b are formed on both end faces as follows: (1) A suitable copper paste is applied to both end faces of the sintered chip, and the copper terminals are formed by baking at a temperature of 600°C to 1000°C in a nitrogen or slightly reducing atmosphere for 1 to 60 minutes. (2) A nickel plating layer and a tin plating layer or other suitable solder composition are further placed on the copper terminals by barrel plating to improve the solderability and prevent oxidation of the copper external electrodes. In this way, a multilayer ceramic capacitor 1 formed of base metal electrodes 3a and 3b and a dielectric ceramic layer 2 containing the dielectric composition disclosed in the present invention is obtained.

[0063] The present invention discloses a dielectric ceramic composition suitable for high temperature applications. Such ceramic formulations can be co-fired with base metal electrodes in a reducing atmosphere. Therefore, the dielectric ceramic composition disclosed herein can be used with non-metallic internal electrodes such as Ni to fabricate multilayer ceramic capacitors.

[0064] Throughout this description, the ranges expressed include all intermediate values ​​with the same number of effective numbers. As a non-limiting example, the range expressed 0.01 to 0.05 includes 0.01, 0.02, 0.03, 0.04, and 0.06. When a range is expressed as a representation with two numbers with different effective numbers, the one with the smallest increment effective number determines the effective number for both. As a non-limiting example, when a range is expressed as 1.0 to 5, this is intended to refer to all numbers from 1.0 to 5.0.

[0065] The following documents are incorporated herein by reference: U.S. Pat. No. 9,564,271 to Banno et al., WO 2018-062084 to Banno, JP 2020-29374A to Takahashi et al., Base Metal Co-fired Multilayer Piezoelectric Materials, Gao et al., Actuators, Vol. 5, Issue 1, p. 8, 2016

[0066] The present invention will now be described with reference to the drawings, which form an integral and non-limiting part of the specification provided for the sake of accuracy of the present invention. Similar elements are numbered accordingly throughout the various drawings. The present invention has been described with reference to preferred embodiments, without limitation thereto. Those skilled in the art will recognize further embodiments illustrated and depicted in the accompanying drawings.

Claims

1. A dielectric ceramic composition comprising: (K ｘ Na ｙ Li ｚ A １－ｘ－ｙ－ｚ ) ｍ (Nｬ ｕ Ta ｖ B ｗ )O ３ The main component is defined by the formula A is at least one element selected from the group consisting of Ca, Sr, and Ba; B is at least one element selected from the group consisting of Ti, Zr, Hf, and Sn; x, y, z, u, v, and w are the mole fractions of each element; m is the molar ratio of A-site and B-site elements; 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0<u<1, 0.0≦w≦0.3, and A principal component where u+v+w=1; A first sub-material including at least one rare earth element selected from the group consisting of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; A second sub-material including at least one transition metal element selected from the group consisting of V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn; a third minor material comprising a frit; The dielectric ceramic composition has a temperature coefficient of capacitance of ±50% over a temperature range of -55°C to 200°C.

2. 2. The dielectric composition according to claim 1, comprising 10 mol % or less of said rare earth element relative to 100 mol % of said main component.

3. 2. The dielectric ceramic composition according to claim 1, comprising 0.05 to 10 mol % of said transition metal relative to 100 mol % of said main component.

4. 2. The dielectric ceramic composition according to claim 1, comprising 0.01 to 15.00 mol % of said frit relative to 100 mol % of said main component.

5. 10. The dielectric ceramic composition of claim 1, wherein the frit comprises a material selected from the group consisting of fluorides, silicates, borides, and oxides.

6. 2. The dielectric ceramic composition according to claim 1, which has a temperature coefficient of capacitance of ±20% over a temperature range of -55°C to 200°C.

7. 2. The dielectric ceramic composition of claim 1 having a dielectric constant of at least 300 at 25°C.

8. 8. The dielectric ceramic composition of claim 7 having a dielectric constant of at least 1000 at 25°C.

9. A multilayer ceramic capacitor comprising: A plurality of dielectric ceramic layers, each of said layers comprising: (K ｘ Na ｙ Li ｚ A １－ｘ－ｙ－ｚ ) ｍ (Nｬ ｕ Ta ｖ B ｗ )O ３ A dielectric composition defined by the formula: A is at least one element selected from the group consisting of Ca, Sr, and Ba; B is at least one element selected from the group consisting of Ti, Zr, Hf, and Sn; x, y, z, u, v, and w are the mole fractions of each element; m is the molar ratio of A-site and B-site elements; 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0<u<1, 0.0≦w≦0.3, and a dielectric composition, wherein u+v+w=1; A first sub-material including at least one rare earth element selected from the group consisting of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; A second sub-material comprising at least one transition metal element selected from the group consisting of V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn; and a third minor material comprising a frit; The dielectric composition comprises a dielectric ceramic layer having a temperature coefficient of capacitance of ±50% over a temperature range of −55° C. to 200° C.; A plurality of internal electrodes including a base metal such as Ni, Cu, or an alloy thereof; a pair of external electrodes formed on each end of a capacitor element body.

10. 10. The multilayer ceramic capacitor according to claim 9, wherein the rare earth element is contained in an amount of 10 mol % or less relative to 100 mol % of the main component.

11. 10. The multilayer ceramic capacitor according to claim 9, wherein the transition metal is contained in an amount of 0.05 to 10 mol % relative to 100 mol % of the main component.

12. 10. The multilayer ceramic capacitor according to claim 9, comprising 0.01 to 15.00 mol % of said frit relative to 100 mol % of said main component.

13. 10. The multilayer ceramic capacitor of claim 9, wherein the frit comprises a material selected from the group consisting of fluorides, silicates, borides, and oxides.

14. 10. The multilayer ceramic capacitor of claim 9, wherein the dielectric composition has a temperature coefficient of capacitance of ±20% over a temperature range of -55°C to 200°C.

15. 10. The multilayer ceramic capacitor of claim 9, wherein the dielectric composition has a dielectric constant of at least 300 at 25°C.

16. 16. The multilayer ceramic capacitor of claim 15, wherein the dielectric composition has a dielectric constant of at least 1000 at 25°C.

17. 1. A method for forming a multilayer ceramic capacitor, comprising: forming a dielectric ceramic precursor; forming a stack of alternating layers of the dielectric ceramic precursor and layers of a metal; compressing the laminate and sintering the dielectric precursor; (K ｘ Na ｙ Li ｚ A １－ｘ－ｙ－ｚ ) ｍ (Nｬ ｕ Ta ｖ B ｗ )O ３ The main component is defined by the formula A is at least one element selected from the group consisting of Ca, Sr, and Ba; B is at least one element selected from the group consisting of Ti, Zr, Hf, and Sn; x, y, z, u, v, and w are the mole fractions of each element; m is the molar ratio of A-site and B-site elements; 0.95≦m≦1.05, 0.05≦x≦0.90, 0.05≦y≦0.90, 0.00≦z≦0.12, 0<u<1, 0.0≦w≦0.3, and Principal component where u+v+w=1, A first sub-material including at least one rare earth element selected from the group consisting of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; A second sub-material comprising at least one transition metal element selected from the group consisting of V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn; and and a third minor material comprising a frit. The dielectric composition has a temperature coefficient of capacitance of ±50% over a temperature range of −55° C. to 200° C.

18. 20. The method of forming a multilayer ceramic capacitor as recited in claim 17, wherein the layers of dielectric ceramic precursor are prepared as ceramic green pastes comprising a mixture of inorganic materials and organic additives, the inorganic solids comprising at least one combination of precursors and dopants.

19. 20. The method of claim 18, further comprising sintering the ceramic green paste.

20. 18. The method of forming a multilayer ceramic capacitor of claim 17, wherein the transition metal is selected from the group consisting of V, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn.

21. 18. The method of forming a multilayer ceramic capacitor of claim 17, wherein the rare earth elements are selected from the group consisting of Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

22. 20. The method of claim 17, wherein the frit comprises at least one compound selected from the group consisting of fluorides, silicates, borides, and oxides.

23. 18. The method of claim 17, wherein the sintering is carried out at a temperature between 900°C and 1350°C.

24. The sintering step may include the steps of: －１６ atm~10 －４ 20. The method of claim 17, carried out in an atmosphere having an oxygen partial pressure of atm.

25. 18. The method of claim 17, wherein the metal is a base metal of Ni, Cu, or an alloy thereof.

26. The method of forming a multilayer ceramic capacitor as recited in claim 17, further comprising forming a pair of external electrodes on each end of the capacitor element body.

27. 18. The method of forming a multilayer ceramic capacitor according to claim 17, wherein the dielectric composition has a temperature coefficient of capacitance of ±20% over a temperature range of -55°C to 200°C.

28. 20. The method of forming a multilayer ceramic capacitor of claim 17, wherein the dielectric composition has a dielectric constant of at least 300 at 25°C.

29. 30. The method of forming a multilayer ceramic capacitor of claim 28, wherein said dielectric composition has a dielectric constant of at least 1000 at 25°C.

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