Dielectric ceramic composition and electronic device

A dielectric ceramic composition having at least a main component of BaTiO.sub.3, a first subcomponent including at least one compound selected from MgO, CaO, BaO, SrO and Cr.sub.2 O.sub.3, a second subcomponent of (Ba, Ca).sub.x,SiO.sub.2+x (where, x=0.8 to 1.2), a third subcomponent including at least one compound selected from V.sub.2 O.sub.5, MoO.sub.3, and WO.sub.3, and a fourth subcomponent including an oxide of R1 (where R1 is at least one element selected from Sc, Er, Tm, Yb, and Lu), wherein the ratios of the subcomponents to 100 moles of the main component of BaTiO.sub.3 are as follows: first subcomponent: 0.1 to 3 moles, second subcomponent: 2 to 10 moles, third subcomponent: 0.01 to 0.5 mole, and fourth subcomponent: 0.5 to 7 moles (where the number of moles of the fourth subcomponent is the ratio of R1 alone). The dielectric ceramic composition has a high relative dielectric constant, has a capacity-temperature characteristic satisfying the X8R characteristic of the EIA standard (-55 to 150.degree. C., .DELTA.C =.+-.15% or less), enables sintering in a reducing atmosphere, has a small change in the capacity under a direct current electric field along with time, and further has a long lifetime of the insulation resistance.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a dielectric ceramic composition having a
 resistance to reduction and to a multi-layer ceramic capacitor or other
 electronic device using the same.
 2. Description of the Related Art
 A multi-layer ceramic capacitor, one type of electronic device, is being
 broadly used as a compact, large capacity, high reliability electronic
 device. The number used in each piece of electronic equipment has also
 become larger. In recent years, along with the increasing miniaturization
 and improved performance of equipment, there have been increasingly
 stronger demands for further reductions in size, increases in capacity,
 reductions in price, and improvements in reliability in multi-layer
 ceramic capacitors.
 Multi-layer ceramic capacitors are normally produced by stacking a paste
 for formation of the internal electrode layers and a paste for formation
 of the dielectric layers using the sheet method or printing method etc.
 and then cofiring the internal electrode layers and dielectric layers in
 the stack.
 As the electroconductive material for the internal electrode layers,
 generally Pd or a Pd alloy is being used, but Pd is high in price and
 therefore relatively inexpensive Ni, Ni alloys, and other base metals have
 been coming into use. When using a base metal as the electroconductive
 material of the internal electrode layers, sintering in the atmosphere
 ends up causing the internal electrode layers to oxidize and therefore the
 cofiring of the dielectric layers and internal electrode layers has to be
 done in a reducing atmosphere. If cofiring in a reducing atmosphere,
 however, the dielectric layers end up being reduced and becoming lower in
 specific resistance. Therefore, nonreducing type dielectric materials are
 being developed.
 Multi-layer ceramic capacitors using nonreducing dielectric materials,
 however, suffer from a remarkable deterioration in the IR (insulation
 resistance) due to application of an electric field, that is, there are
 the problems that the IR lifetime is short and the reliability is low.
 Further, if a dielectric is exposed to a direct current electric field, the
 problem arises of the specific dielectric constant .di-elect cons..sub.r
 falling along with time. If the dielectric layers are made thinner so as
 to reduce the size of the chip capacitor and increase its capacity, the
 electric field acting on the dielectric layers will become stronger when
 the direct current voltage is applied, so the change in the specific
 dielectric constant .di-elect cons..sub.r along with time, that is, the
 change in the capacity along with time, will end up becoming much larger.
 Further, a capacitor is also required to be excellent in temperature
 characteristic. In particular, in some applications, it is desired that
 the temperature characteristic be smooth under harsh conditions. In recent
 years, multi-layer ceramic capacitors have come into use for various types
 of electronic equipment such as the engine electronic control units (ECU)
 mounted in the engine compartments of automobiles, crank angle sensors,
 antilock brake system (ABS) modules, etc. These electronic equipment are
 used for stabilizing engine control, drive control, and brake control, and
 therefore are required to have excellent circuit temperature stability.
 The environment in which these electronic equipment are used is envisioned
 to be one in which the temperature falls to as low as -20.degree. C. or so
 in the winter in cold areas or the temperature rises to as high as
 +130.degree. C. or so in the summer right after engine startup. Recently,
 there has been a trend toward reduction of the number of wire harnesses
 used for connecting electronic apparatuses and the equipment they control.
 Electronic apparatuses are also being mounted outside of the vehicles in
 some cases. Therefore, the environment is becoming increasingly severe for
 electronic apparatuses. Accordingly, the capacitors used for these
 electronic apparatuses have to have smooth temperature characteristics in
 a broad temperature range.
 As tempetature-compensating capacitor materials superior in temperature
 characteristics, (Sr, Ca)(Ti, Zr)O.sub.3 based, Ca(Ti, Zr)O.sub.3 based,
 Nd.sub.2 O.sub.3 --2TiO.sub.2 based, La.sub.2 O.sub.3 --2TiO.sub.2 based,
 and other materials are generally known, but these compositions have
 extremely low specific dielectric constants (generally less than 100), so
 it is substantially impossible to produce a capacitor having a large
 capacity.
 As a dielectric ceramic composition having a high dielectric constant and a
 smooth capacity-temperature characteristic, a composition comprised of
 BaTiO.sub.3 as a main component plus Nb.sub.2 O.sub.5 --Co.sub.3 O.sub.4,
 MgO--Y, rare earth elements (Dy, Ho, etc.), Bi.sub.2 O.sub.3 --TiO.sub.2,
 etc. is known. Looking at the temperature characteristic of a dielectric
 ceramic composition comprising BaTiO.sub.3 as a main component, since the
 Curie temperature of pure BaTiO.sub.3 is close to about 130.degree. C., it
 is extremely difficult to satisfy the R characteristic of the
 capacity-temperature characteristic (.DELTA.C=.+-.15% or less) in the
 region higher in temperature than that. Therefore, a BaTiO.sub.3 based
 high dielectric constant material can only satisfy the X7R characteristic
 of the EIA standard (-55 to 125.degree. C., .DELTA.C=.+-.15% or less). If
 only satisfying the X7R characteristic, the material is not good enough
 for an electronic apparatus of an automobile which is used in the
 above-mentioned harsh environments. An electronic apparatus requires a
 dielectric ceramic composition satisfying the X8R characteristic of the
 EIA standard (-55 to 150.degree. C., .DELTA.C=.+-.15% or less).
 To satisfy the X8R characteristic in a dielectric ceramic composition
 comprised of BaTiO.sub.3 as a main component, it has been proposed to
 shift the Curie temperature to the high temperature side by replacing the
 Ba in the BaTiO.sub.3 with Bi, Pb, etc. (Japanese Unexamined Patent
 Publication (Kokai) Nos. 10-25157 and 9-40465). Further, it has also been
 proposed to satisfy the X8R characteristic by selecting a BaTiO.sub.3
 +CaZrO.sub.3 +ZnO+Nb.sub.2 O.sub.5 based composition (Japanese Unexamined
 Patent Publication (Kokai) No. 4-295048, No. 4-292458, No. 4-292459, No.
 5-109319, and No. 6-243721). In each of these compositions as well,
 however, since the easily vaporized and diffusing Pb, Bi, and Zn are used,
 sintering in air or another oxidizing atmosphere becomes a prerequisite.
 Therefore, there are the problems that it is not possible to use an
 inexpensive base metal such as Ni for the internal electrodes of the
 capacitor and it is necessary to use Pd, Au, Ag, or another high priced
 precious metal.
 SUMMARY OF THE INVENTION
 The object of the present invention is to provide a dielectric ceramic
 composition having a high specific dielectric constant, having a
 capacity-temperature characteristic satisfying the X8R characteristic of
 the EIA standard (-55 to 150.degree. C., .DELTA.C=.+-.15% or less),
 enabling sintering in a reducing atmosphere, having a small change in the
 capacity under a direct current electric field along with time, and
 further having a long lifetime of the insulation resistance and, further,
 to provide a multi-layer ceramic capacitor or other electronic device
 using this dielectric ceramic composition.
 To achieve the above object, the dielectric ceramic composition according
 to the first aspect of the present invention is a dielectric ceramic
 composition comprising at least:
 a main component of BaTiO.sub.3,
 a first subcomponent including at least one compound selected from MgO,
 CaO, BaO, SrO and Cr.sub.2 O.sub.3,
 a second subcomponent of (Ba, Ca).sub.x SiO.sub.2+x (where, x=0.8 to 1.2),
 a third subcomponent including at least one compound selected from V.sub.2
 O.sub.5, MoO.sub.3, and WO.sub.3, and
 a fourth subcomponent including an oxide of R1 (where R1 is at least one
 element selected from Sc, Er, Tm, Yb, and Lu), wherein
 the ratios of the subcomponents to 100 moles of the main component of
 BaTiO.sub.3 are:
 first subcomponent: 0.1 to 3 moles,.
 second subcomponent: 2 to 10 moles,
 third subcomponent: 0.01 to 0.5 mole, and
 fourth subcomponent: 0.5 to 7 moles (where the number of moles of the
 fourth subcomponent is the ratio of R1 alone).
 Note that the ratios of Ba and Ca in the second subcomponent can be any
 ratios and a subcomponent containing just one of Ba and Ca is also
 possible. Preferably, the dielectric ceramic composition according to the
 present invention further comprises as a fifth subcomponent an oxide of R2
 (where R2 is at least one element selected from Y, Dy, Ho, Th, Gd and Eu),
 where the content of the fifth subcomponent being not more than 9 moles
 with respect to 100 moles of the main component of BaTiO.sub.3 (where the
 number of moles of the fifth subcomponent is the ratio of R2 alone).
 Further, preferably, the total content of the fourth subcomponent and the
 fifth subcomponent is not more than 13 moles with respect to 100 moles of
 the main component of BaTiO.sub.3 (where the numbers of moles of the
 fourth subcomponent and fifth subcomponent are the ratios of R1 and R2
 alone), more preferably not more than 10 moles.
 Further, preferably, the dielectric ceramic composition according to the
 present invention further comprises as a sixth subcomponent MnO, the
 content of the sixth subcomponent being not more than 0.5 mole with
 respect to 100 moles of the main component of BaTiO.sub.3.
 The dielectric ceramic composition according to a second aspect of the
 present invention is a dielectric ceramic composition containing
 BaTiO.sub.3 as a main component, wherein
 X-ray diffraction using Cu-K.alpha.-rays reveals a pseudo cubic peak
 including a (002) peak and (200) peak in the range of 2.theta.=44 to
 46.degree., the half-width of the pseudo cubic peak is at least
 0.3.degree., and, when the intensity of the (002) peak is I(002) and the
 intensity of the (200) peak is I(200), I(002) .gtoreq.I(200).
 The dielectric ceramic composition according to a third aspect of the
 present invention is a dielectric ceramic composition containing
 BaTiO.sub.3 as a main component, wherein
 when the value of the heat flow difference per unit time (dq/dt) measured
 by DSC (differential scan calorimetry) differentiated by temperature is
 DDSC, the temperature difference between the pair of peaks present at the
 two sides of the Curie temperature in a graph of the relationship between
 temperature and the DDSC is at least 4.1.degree. C.
 If the peak in the graph showing the relationship between the temperature
 and ethe DDSC is not clear enough, the dielectric ceramic composition
 wherein the half-width in the graph showing the relationship between the
 temperature and the DSC is at least 4.1.degree. C. corresponds to the
 dielectric ceramic composition according to the third aspect of the
 present invention. The half-width is defined to be a temperature
 difference between the two points sandwiching the peak, wherein a line
 linking the two points and extending in parallel to a base line of the
 endothermic peak in the graph showing the relationship between the
 temperature and the DSC has the half width of the base line.
 An electronic device according to the present invention is not particularly
 limited so long as it is an electronic device having a dielectric layer.
 For example, it is a multi-layer ceramic capacitor device having a
 capacitor device body comprised of the dielectric layers and internal
 electrode layers alternately stacked. In the present invention, the
 dielectric layer is comprised of any of the above dielectric compositions.
 The electroconductive material included in the internal electrode layer is
 not particularly limited, but for example is Ni or an Ni alloy.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Multi-layer Ceramic Capacitor
 As shown in FIG. 1, the multi-layer ceramic capacitor according to one
 embodiment of the present invention has a capacitor device body 10 of a
 configuration of dielectric layers 2 and internal electrode layers 3
 stacked alternately. At the two ends of the capacitor device body 10 are
 formed a pair of external electrodes 4 conductive with the internal
 electrode layers 3 alternately arranged inside the device body 10. The
 shape of the capacitor device body 10 is not particularly limited, but
 normally is made a parallelepiped. Further, the dimensions are not
 particularly limited and may be made suitable dimensions in accordance
 with the application. Usually, however, they are (0.6 to 5.6 mm)
 .times.(0.3 to 5.0 mm) .times.(0.3 to 1.9 mm).
 The internal electrode layers 3 are stacked so that end faces thereof
 alternately protrude out to the surfaces of the two opposing ends of the
 capacitor device body 10. The pair of external electrodes 4 are formed at
 the two ends of the capacitor device body 10 and are connected to the
 exposed end faces of the alternately arranged internal electrode layers 3.
 Dielectric Layers 2
 Each of the dielectric layers 2 contains the dielectric ceramic composition
 of the present invention.
 The dielectric ceramic composition of the present invention is comprised of
 a dielectric ceramic composition comprising at least:
 a main component of BaTiO.sub.3,
 a first subcomponent including at least one compound selected from MgO,
 CaO, BaO, SrO and Cr.sub.2 O.sub.3,
 a second subcomponent of (Ba, Ca).sub.x Sio.sub.2+x (where, x=0.8 to 1.2),
 a third subcomponent including at least one compound selected from V.sub.2
 O.sub.5, MoO.sub.3, and WO.sub.3, and
 a fourth subcomponent including an oxide of R1 (where R1 is at least one
 element selected from Sc, Er, Tm, Yb, and Lu).
 The ratios of the subcomponents to the main component of BaTiO.sub.3 are,
 with respect to 100 moles of the BaTiO.sub.3 :
 first subcomponent: 0.1 to 3 moles,
 second subcomponent: 2 to 10 moles,
 third subcomponent: 0.01 to 0.5 mole, and
 fourth subcomponent: 0.5 to 7 moles, preferably
 first subcomponent: 0.5 to 2.5 moles,
 second subcomponent: 2.0 to 5.0 moles,
 third subcomponent: 0.1 to 0.4 mole, and
 fourth subcomponent: 0.5 to 5.0 moles,
 Note that the ratio of the fourth subcomponent is not the molar ratio of
 the R1 oxide, but the molar ratio of R1 alone. That is, when for example
 using an oxide of Yb as the fourth subcomponent, a ratio of the fourth
 subcomponent of 1 mole does not mean the ratio of the Yb.sub.2 O.sub.3 is
 1 mole, but the ratio of Yb is 1 mole.
 In this specification, the oxides constituting the main component and the
 subcomponents are expressed by stoichiochemical compositions, but the
 oxidized state of the oxides may also deviate from the stoichiochemical
 compositions. The ratios of the subcomponents, however, are found by
 conversion from the amounts of the metals contained in the oxides
 constituting the subcomponents to the oxides of the above stoichiochemical
 compositions.
 The reasons for limiting the contents of the above subcomponents are as
 follows.
 If the content of the first subcomponent (MgO, CaO, BaO, SrO, and Cr.sub.2
 O.sub.3) is too small, the rate of change of the capacity-temperature
 characteristic ends up becoming large. On the other hand, if the content
 is too large, the sinterability deteriorates. Note that the ratios of the
 oxides in the first subcomponent may be any ratios.
 The BaO and the CaO in the second subcomponent [(Ba, Ca).sub.x SiO.sub.2+x
 ] are also contained in the first subcomponent, but the composite oxide
 (Ba, Ca).sub.x SiO.sub.2+x has a low melting point, so it has good
 reactivity with the main component. Therefore, in the present invention,
 the BaO and/or CaO are also added as the above composite oxide. If the
 content of the second subcomponent is too small, the capacity-temperature
 characteristic becomes poor and the IR (insulation resistance) falls. On
 the other hand, if the content is too great, the IR lifetime becomes
 insufficient and, further, the dielectric constant ends up falling
 rapidly. The x in the (Ba, Ca).sub.x SiO.sub.2+x is preferably 0.8 to 1.2,
 more preferably 0.9 to 1.1. If x is too small, that is, if the SiO.sub.2
 is too great, the main component of BaTiO.sub.3 will be reacted with and
 the dielectric property will end up deteriorating. On the other hand, if x
 is too large, the melting point will become high and the sinterability
 will be deteriorated, so this is not preferable. Note that the ratios of
 Ba and Ca in the second subcomponent are any ratios. A subcomponent
 containing just one is also possible.
 The third subcomponent (V.sub.2 O.sub.5, MoO.sub.3, and WO.sub.3) exhibits
 the effect of smoothing the capacity-temperature characteristic above the
 Curie temperature and the effect of improving the IR lifetime. If the
 content of the third subcomponent is too small, these effects become
 insufficient. On the other hand, if the content is too great, the IR
 remarkably falls. Note that the ratios of the oxides in the third
 subcomponent may be any ratios.
 The fourth subcomponent (R1 oxide) exhibits the effect of shifting the
 Curie temperature to the high temperature side and the effect of smoothing
 the capacity-temperature characteristic. If the content of the fourth
 subcomponent is too small, these effects become insufficient and the
 capacity-temperature characteristic ends up deteriorating. On the other
 hand, if the content is too large, the sinterability tends to deteriorate.
 Among the fourth subcomponents, a Yb oxide is preferred since it has a
 high effect on improvement of the characteristic and further is
 inexpensive in cost.
 The dielectric ceramic composition of the present invention preferably, in
 accordance with need, contains as a fifth subcomponent an R2 oxide (where,
 R2 is at least one element selected from Y, Dy, Ho, Tb, Gd and Eu). The
 fifth subcomponent (R2 oxide) exhibits the effect of improvement of the IR
 and the IR lifetime and has little adverse effect on the
 capacity-temperature characteristic. If the content of the R2 oxide is too
 large, however, the sinterability tends to deteriorate. Among the fifth
 subcomponents, a Y oxide is preferred since it has a high effect on
 improvement of the characteristic and further is inexpensive in cost.
 The total content of the fourth subcomponent and the fifth subcomponent is
 preferably not more than 13 moles, more preferably not more than 10 moles,
 with respect to 100 moles of the main component of BaTiO.sub.3 (where the
 numbers of moles of the fourth subcomponent and the fifth subcomponent are
 ratios of R1 and R2 alone). This is to keep the sinterability good.
 Further, the dielectric ceramic composition of the present invention may
 contain as a sixth subcomponent MnO. This sixth subcomponent exhibits the
 effect of promotion of sintering, the effect of an increase of the IR, and
 an effect of improvement of the IR lifetime. To sufficiently obtain these
 effects, the ratio of the sixth subcomponent with respect to 100 moles of
 the BaTiO.sub.3 is preferably at least 0.01 mole. If the content of the
 sixth subcomponent is too large, there is an adverse effect on the
 capacity-temperature characteristic, so the content is preferably made not
 more than 0.5 mole.
 Further, the dielectric ceramic composition of the present invention may
 also contain Al.sub.2 O.sub.3 in addition to the above oxides. Al.sub.2
 O.sub.3 does not have much of an effect on the capacity-temperature
 characteristic and exhibits the effect of improvement of the
 sinterability, IR, and IR lifetime. If the content of the Al.sub.2 O.sub.3
 is too large, however, the sinterability deteriorates and the IR falls, so
 the Al.sub.2 O.sub.3 is preferably included in an amount of not more than
 1 mole with respect to 100 moles of the BaTiO.sub.3, more preferably not
 more than 1 mole of the dielectric ceramic composition as a whole.
 Note that when at least one element of Sr, Zr, and Sn replaces the Ba or Ti
 in the main component constituting the perovskite structure, the Curie
 temperature shifts to the low temperature side, so the
 capacity-temperature characteristic above 125.degree. C. deteriorates.
 Therefore, it is preferable not to use a BaTiO.sub.3 containing these
 elements for example, [(Ba, Sr)TiO.sub.3 ] as a main component. There is
 however no particular problem with a level contained as an impurity (less
 than 0.1 mol% of the dielectric ceramic composition as a whole).
 The average grain size of the dielectric ceramic composition of the present
 invention is not particularly limited and may be suitably determined in
 accordance with the thickness of the dielectric layers etc. from the range
 of for example 0.1 to 3.0 ,.mu.m. The capacity-temperature characteristic
 deteriorates the thinner the dielectric layers are and tends to
 deteriorate the smaller the average grain is in size. Therefore, the
 dielectric ceramic composition of the present invention is particular
 effective when having to make the average grain size small, specifically,
 when the average grain size is 0.1 to 0.5 .mu.m. Further, if the average
 grain size is made small, the IR lifetime becomes longer and further the
 change in the capacity under a direct current electric field over time
 becomes smaller, so it is preferable that the average grain size be small
 as explained above from this viewpoint as well.
 The Curie temperature of the dielectric ceramic composition of the present
 invention (phase transition temperature from strong dielectric to ordinary
 dielectric) may be changed by selecting the composition, but to satisfy
 the X8R characteristic, it is, preferably made at least 120.degree. C.,
 more preferably at least 123.degree. C. Note that the Curie temperature
 may be measured using DSC (differential scan calorimetry).
 The thickness of the dielectric layers comprised of the dielectric ceramic
 composition of the present invention is normally not more than 40.mu.m,
 particularly not more than 30.mu.m, per layer. The lower limit of the
 thickness is normally about 2.mu.m. The dielectric ceramic composition of
 the present invention is effective for the improvement of the
 capacity-temperature characteristic of a multi-layer ceramic capacitor
 having such thinned dielectric layers. Note that the number of the
 dielectric layers stacked is normally 2 to 300 or so.
 The multi-layer ceramic capacitor using the dielectric ceramic composition
 of the present invention is suitable for use as an electronic device for
 equipment used at over 80.degree. C., in particular in an environment of
 125 to 150.degree. C. Further, in this temperature range, the temperature
 characteristic of the capacity satisfies the R characteristic of the EIA
 standard and also satisfies the X8R characteristic. It is also possible to
 simultaneously satisfy the B characteristic of the EIAJ standard [rate of
 change of capacity of within .+-.10% at -25 to 85.degree. C. (reference
 temperature 20.degree. C.)] and the X7R characteristic of the EIA standard
 (-55 to 125 .degree. C., .DELTA.C=.+-.15% or less).
 In a multi-layer ceramic capacitor, the dielectric layers are normally
 subjected to an alternating current electric field of from 0.02V/.mu.m, in
 particular from 0.2.mu.m, further from 0.5V/.mu.m, to generally not more
 than 5V/.mu.m and a direct current electric field of not more than
 5V/.mu.m superposed over this, but the temperature characteristic of the
 capacity is extremely stable even when such electric fields are applied.
 The dielectric ceramic composition of the present invention includes a
 dielectric ceramic composition having BaTiO.sub.3 as its main component
 which satisfies the following condition in X-ray diffraction using
 Cu-K.alpha. rays. The conditions are that a (002) peak and (200) peak be
 observed overlappingly in the range of 2.theta.=44 to 46.degree. as a
 pseudo cubic peak, that the half width of the pseudo cubic peak be at
 least 0.3.degree., and, when the intensity of the (002) peak is I(002) and
 the intensity of the (200) peak is I(200), I(002).gtoreq.I(200). By
 satisfying these conditions, the capacity-temperature characteristic is
 improved and the X8R characteristic can be satisfied.
 Note that the measurement conditions in the X-ray diffraction are not
 particularly limited, but the following measurement conditions are
 normally used to obtain a resolution of a degree enabling the half width
 to be discerned.
 Scan width: not more than 0.05.degree.
 Scan rate: not more than 0.1.degree. /minute
 X-ray detection conditions
 Parallel slits: not more than 1.degree.
 Dispersion slits: not more than 1.degree.
 Light receiving slits: not more than 0.3 mm
 The dielectric ceramic composition containing the above first to fourth
 subcomponents as essential components can satisfy the above conditions in
 X-ray diffraction, but even other compositions of dielectric ceramic
 compositions can satisfy the above conditions in X-ray diffraction by
 suitably controlling the composition and the manufacturing conditions.
 Further, the present invention includes a dielectric ceramic composition
 containing BaTiO.sub.3 as a main component which exhibits the following
 characteristics in DSC (differential scan calorimetry). DSC is a method
 for measurement finding the relationship between the temperature and the
 heat flow difference (dq/dt) per unit time and is used for measurement of
 the Curie temperature etc. The value of the heat flow difference
 differentiated by the temperature (hereinafter referred to as the DDSC)
 becomes 0 in the Curie temperature. Graphing the relationship between the
 temperature and DDSC, there is a plus DDSC peak at the low temperature
 side of the Curie temperature and a minus DDSC peak at the high
 temperature side. This dielectric ceramic composition having the
 characteristic of a distance between these two peaks (temperature
 difference) of at least 4.1 .degree. C., preferably at least 6.degree. C.,
 becomes excellent in the temperature characteristic of the capacity and
 can satisfy the X8R characteristic.
 A dielectric ceramic composition containing the above first to fourth
 subcomponents as essential components can satisfy the above characteristic
 in DSC, but even other compositions of dielectric ceramic compositions can
 satisfy the above characteristic in DSC by suitably controlling the
 composition and the manufacturing conditions.
 Internal Electrode Layers 3
 The electroconductive material contained in the internal electrode layers 3
 is not particularly limited, but a base metal may be used since the
 material constituting the dielectric layers 2 has a resistance to
 reduction. As the base metal used as the electroconductive material, Ni or
 an Ni alloy is preferable. As the Ni alloy, an alloy of at least one type
 of element selected from Mn, Cr, Co, and Al with Ni is preferable. The
 content of the Ni in the alloy is preferably not less than 95 wt%.
 Note that the Ni or Ni alloy may contain P and other various types of trace
 components in amounts of not more than 0.1 wt% or so.
 The thickness of the internal electrode layer may be suitably determined in
 accordance with the application etc., but is usually 0.5 to 5 .mu.m, in
 particular 0.5 to 2.5 .mu.m or so is preferable.
 External Electrodes 4
 The electroconductive material contained in the external electrodes 4 is
 not particularly limited, but in the present invention an inexpensive Ni,
 Cu, or alloys of the same may be used.
 The thickness of the external electrodes may be suitably determined in
 accordance with the application etc., but is usually 10 to 50 .mu.m or so.
 Method of Manufacturing Multi-Layer Ceramic Capacitor
 The multi-layer ceramic capacitor using the dielectric ceramic composition
 of the present invention, like the conventional multi-layer ceramic
 capacitor, is produced by preparing a green chip using the usual printing
 method or sheet method which uses pastes, sintering the green chip, then
 printing or transferring and sintering the external electrodes. The method
 of manufacture will be explained in detail below.
 The dielectric layer paste may be an organic-based paint comprised of a
 mixture of a dielectric ingredient and an organic vehicle and may also be
 a water-based paint.
 For the dielectric ingredient, use may be made of the above-mentioned
 oxides or mixtures thereor or composite oxides, but it is also possible to
 suitably select and mix for use various compounds forming the above oxides
 or composite oxides by sintering, for example, carbonates, oxalates,
 nitrates, hydroxides, and organic metal compounds. The content quantity of
 the compounds in the dielectric ingredient may be suitably determined so
 as to give the above-mentioned composition of the dielectric ceramic
 composition after sintering.
 The dielectric ingredient is normally used as a powder of an average
 particle size of 0.1 to 3 .mu.m.
 The organic vehicle is comprised of a binder dissolved in an organic
 solvent. The binder used for the organic vehicle is not particularly
 limited, but may be suitably selected from ethyl cellulose, polyvinyl
 butyral, and other ordinary types of binders. Further, the organic solvent
 used is also not particularly limited and may be suitably selected from
 terpineol, butyl carbitol, acetone, toluene, and other organic solvents in
 accordance with the printing method, sheet method, or other method of use.
 Further, when using a water-based paint as the dielectric layer paste, it
 is sufficient to knead a water-based vehicle comprised of a water-based
 binder or dispersant etc. dissolved in water together with the dielectric
 layer ingredient. The water-based binder used for the water-based vehicle
 is not particularly limited. For example, a polyvinyl alcohol, cellulose,
 water-based acrylic resin, etc. may be used.
 The internal electrode layer paste is prepared by kneading the
 electroconductive material comprised of the above various types of
 dielectric metals and alloys or various types of oxides forming the above
 electroconductive materials after sintering, an organic metal compound,
 resinate, etc. together with the above organic vehicle.
 The external electrode paste may be prepared in the same way as the above
 internal electrode layer paste.
 The content of the organic vehicle in the above pastes is not particularly
 limited and may fall within the usual content, for example, the binder may
 be contained in an amount of 1 to 5 wt% Or so and the solvent 10 to 50 wt%
 or so. Further, the pastes may include, in accordance with need, various
 types of additives selected from dispersants, plasticizers, dielectrics,
 insulators, etc. The total content of these is preferably not more than 10
 wt%.
 When using a printing method, the dielectric layer paste and the internal
 electrode layer paste are successively printed on the PET or other
 substrate. The result is then cut into a predetermined shape, then the
 pastes are peeled off from the substrate to form a green chip.
 Further, when using a sheet method, a dielectric layer paste is used to
 form a green sheet, the internal electrode layer paste is printed on top
 of this, then these are stacked to form a green chip.
 Before sintering, the green chip is processed to remove the binder. This
 processing for removing the binder may be performed under ordinary
 conditions, but when using Ni or an Ni alloy or other base metal for the
 electroconductive material of the internal electrode layer, this is
 preferably performed under the following conditions:
 Rate of temperature rise: 5 to 300.degree. C./hour, in particular 10 to
 100.degree. C./hour
 Holding temperature: 180 to 400.degree. C., in particular 200 to
 300.degree. C.
 Temperature holding time: 0.5 to 24 hours, in particular 5 to 20 hours
 Atmosphere: in the air
 The atmosphere when sintering the green chip may be suitably determined in
 accordance with the type of the electroconductive material in the internal
 electrode layer paste, but when using Ni or an Ni alloy or other base
 metal as the electroconductive material, the oxygen partial pressure in
 the sintering atmosphere is preferably made 10.sup.-8 to 10.sup.-15
 atmospheres. If the oxygen partial pressure is less than this range, the
 electroconductive material of the internal electrode layers becomes
 abnormally sintered and ends up breaking in the middle in some cases.
 Further, if the oxygen partial pressure is more than the above range, the
 internal electrode layers tend to oxidize.
 Further, the holding temperature at the time of sintering is preferably
 1100 to 1400.degree. C., more preferably 1200 to 1360.degree. C., still
 more preferably 1200 to 1320.degree. C. If the holding temperature is less
 than the above range, the densification becomes insufficient, while if
 over that range, there is a tendency toward breaking of the electrodes due
 to abnormal sintering of the internal electrode layers, deterioration of
 the capacity-temperature characteristic due to dispersion of the material
 comprising the internal electrode layers, and reduction of the dielectric
 ceramic composition.
 The various conditions other than the above conditions are preferably
 selected from the following ranges:
 Rate of temperature rise: 50 to 500.degree. C./hour, in particular 200 to
 300.degree. C./hour
 Temperature holding time: 0.5 to 8 hours, in particular 1 to 3 hours
 Cooling rate: 50 to 500.degree. C./hour, in particular 200 to 300.degree.
 C./hour
 Note that the sintering atmosphere is preferably a reducing atmosphere. As
 the atmospheric gas, for example, it is preferable to use a wet mixed gas
 of N.sub.2 and H.sub.2.
 When sintering in a reducing atmosphere, the capacitor device body is
 preferably annealed. The annealing process is for reoxidizing the
 dielectric layer. Since this enables the IR lifetime to be remarkably
 prolonged, the reliability is improved.
 The oxygen partial pressure in the annealing atmosphere is preferably not
 less than 10.sup.-9 atmospheres, in particular 10.sup.-6 to 10.sup.-9
 atmospheres. If the oxygen partial pressure is less than the above range,
 reoxidation of the dielectric layer is difficult, while if over that
 range, the internal electrode layers tend to oxide.
 The holding temperature at the time of annealing is preferably not more
 than 1100.degree. C., in particular 500 to 1100.degree. C. If the holding
 temperature is less than the above range, the oxidation of the dielectric
 layers becomes insufficient, so the IR tends to become low and the IR
 lifetime short. On the other hand, when the holding temperature exceeds
 the above range, not only do the internal electrode layers oxidize and the
 capacity fall, but also the internal electrode layers end up reacting with
 the dielectric material resulting in a tendency toward deterioration of
 the capacity-temperature characteristic, a fall in the IR, and a fall in
 the IR lifetime. Note that the annealing may be comprised of only a
 temperature raising process and temperature reducing process. That is, the
 temperature holding time may also be made zero. In this case, the holding
 temperature is synonomous with the maximum temperature.
 The various conditions other than the above conditions are preferably
 determined from the following ranges:
 Temperature holding time: 0 to 20 hours, in particular 6 to 10 hours
 Cooling rate: 50 to 500.degree. C./hour, in particular 100 to 300.degree.
 C./hour
 Note that for the atmospheric gas, wet N.sub.2 gas etc. may be used.
 In the processing for removing the binder, the sintering, and the
 annealing, for example, a wetter etc. may be used to wet the N.sub.2 gas
 or mixed gas. In this case, the temperature of the water is preferably 5
 to 75.degree. C.
 The processing for removing the binder, sintering, and annealing may be
 performed consecutively or independently. When preferably performing these
 consecutively, after processing to remove the binder, the atmosphere is
 changed without cooling, then the temperature is raised to the holding
 temperature for sintering, the sintering performed, then the chip is
 cooled, the atmosphere is changed when the holding temperature of the
 annealing is reached, and then annealing is performed. On the other hand,
 when performing these independently, at the time of sintering, preferably
 the temperature is raised to the holding temperature at the time of the
 processing for removing the binder in an N.sub.2 gas or wet N.sub.2 gas
 atmosphere, then the atmosphere is changed and the temperature is further
 raised. Preferably, the chip is cooled to the holding temperature of the
 annealing, then the atmosphere changed again to an N.sub.2 gas or wet
 N.sub.2 gas atmosphere and the cooling continued. Further, at the time of
 annealing, the temperature may be raised to the holding temperature in an
 N.sub.2 gas atmosphere, then the atmosphere changed or the entire
 annealing process may be performed in a wet N.sub.2 gas atmosphere.
 The thus obtained capacitor device body is, for example, end polished using
 barrel polishing or sandblasting etc., then printed or transferred with an
 external electrode paste and sintered to form the external electrodes 4.
 The sintering conditions of the external electrode paste are for example
 preferably 600 to 800.degree. C. for 10 minutes to 1 hour or so in a wet
 mixed gas of N.sub.2 and H.sub.2. Further, in accordance with need, the
 surfaces of the external electrodes 4 may be formed with a covering layer
 using plating technique etc.
 The thus produced multi-layer ceramic capacitor of the present invention is
 mounted by soldering it onto a printed circuit board for use in various
 types of electronic equipment.
 Note that the present invention is not limited to the above embodiments and
 may be modified in various ways within the scope of the invention.
 For example, in the above embodiments, illustration was made of a
 multi-layer ceramic capacitor as the electronic device according to the
 present invention, but the electronic device according to the present
 invention is not limited to a multi-layer ceramic capacitor and may be any
 device having a dielectric layer comprised of a dielectric ceramic
 composition of the above composition.
 [EXAMPLES ]
 Below, the present invention will be explained with reference to more
 detailed examples, but the present invention is not limited to these
 examples.
 EXAMPLE 1
 Samples of multi-layer ceramic capacitors were fabricated by the procedure
 explained below.
 First, the following pastes were prepared.
 Dielectric Layer Paste
 Ingredients of the main component and ingredients of the subcomponents with
 particle sizes of 0.1 to 1 .mu.m were prepared. A carbonate was used for
 the ingredients of MgO and MnO and an oxide was used for the other
 ingredients. Further, (Ba.sub.0.6 Ca.sub.0.4)SiO.sub.3 was used for the
 ingredient of the second subcomponent. Note that (Ba.sub.0.6
 Ca.sub.0.4)SiO.sub.3 was produced by wet mixing BaCO.sub.3, CaCO.sub.3,
 and SiO.sub.2 using a ball mill for 16 hours, drying the mixture,
 sintering it at 1150.degree. C. in air, then wet pulverizing it using a
 ball mill for 100 hours.
 These ingredients were blended to give compositions after sintering shown
 in the following Table 1 to Table 4. These were wet-mixed using a ball
 mill, then dried.
 100 parts by weight of the dried ingredient of the dielectric, 4.8 parts by
 weight of acrylic resin, 40 parts by weight of methylene chloride, 20
 parts by weight of ethyl acetate, 6 parts by weight of mineral spirits,
 and 4 parts by weight of acetone were mixed using a ball mill to make a
 paste.
 Internal Electrode Layer Paste
 100 parts by weight of Ni particles of an average particle size of 0.2 to
 0.8 .mu.m, 40 parts by weight of an organic vehicle (8 parts by weight of
 an ethyl cellulose resin dissolved in 92 parts by weight of butyl
 carbitol), and 10 parts by weight of butyl carbitol were kneaded using a
 triple-roll to make a paste.
 External Electrode Paste
 100 parts by weight of Cu particles of an average particle size of 0.5
 .mu.m, 35 parts by weight of an organic vehicle (8 parts by weight of an
 ethyl cellulose resin dissolved in 92 parts by weight of butyl carbitol),
 and 7 parts by weight of butyl carbitol were kneaded together to make a
 paste.
 Preparation of Green Chip
 The above dielectric layer paste was used to form a green sheet on a PET
 film. An internal electrode paste was printed on this, then the sheet was
 peeled from the PET film. Next, the green sheets and protective green
 sheets (ones without the internal electrode layer paste printed on it)
 were stacked and pressed to obtain a green chip.
 Sintering
 First, the green chip was cut to a predetermined size and was processed to
 remove the binder, sintered, and annealed under the following conditions,
 then formed with external electrodes to obtain the multi-layer ceramic
 capacitor of the configuration shown in FIG. 1.
 Conditions for Processing to Remove Binder
 Rate of temperature rise: 15.degree. C./hour
 Holding temperature: 280.degree. C.
 Temperature holding time: 8 hours
 Atmosphere: in the air
 Sintering Conditions
 Rate of temperature rise: 200.degree. C./hour
 Holding temperature: temperature shown in Table 1 to Table 4
 Temperature holding time: 2 hours
 Cooling rate: 300.degree. C./hour
 Atmospheric gas: wet N.sub.2 +H.sub.2 mixed gas
 Oxygen partial pressure: 10.sup.-11 atmospheres
 Annealing Conditions
 Holding temperature: 900.degree. C.
 Temperature holding time: 9 hours
 cooling rate: 300.degree. C./hour
 Atmospheric gas: wet N.sub.2 gas
 Oxygen partial pressure: 10.sup.-7 atmospheres
 Note that for the wetting of the atmospheric gas at the time of sintering
 and annealing, a wetter with a water temperature of 35.degree. C. was
 used.
 External Electrodes
 The external electrodes were formed by polishing the end faces of the
 sintered body by sandblasting, then transferring the external electrode
 paste to the end faces and sintering them there in a wet N.sub.2 +H.sub.2
 atmosphere at 800.degree. C. for 10 minutes.
 The thus obtained samples had a size of 3.2 mm .times.1.6 mm .times.0.6 mm,
 had four dielectric layers sandwiched between internal electrode layers,
 and had a thickness of 10 .mu.m. The thickness of each internal electrode
 layer was 2.0 .mu.m.
 Further, for comparison, samples not containing the fourth subcomponent and
 samples containing other rare earth elements instead of the rate earth
 elements of the fourth subcomponent were also prepared. The other rare
 earth elements are listed in the columns of the fourth subcomponent in the
 tables.
 Disk-shaped samples were also prepared in addition to the samples of the
 capacitors. These disk-shaped samples were of the same compositions of the
 samples of the above capacitors and were sintered under the same
 conditions. In-Ga electrodes of diameters of 5 mm were coated on the two
 surfaces of the samples.
 The samples were evaluated as to the following characteristics.
 Relative Dielectric Constant (.di-elect cons..sub.r) and Dielectric Loss
 (tan.delta.)
 The capacity and tan.delta.of the disk-shaped samples were measured at
 25.degree. C. by an LCR meter under conditions of 1 kHz and 1 Vrms.
 Further, the relative dielectric constant was calculated from the
 capacity, electrode dimensions, and thickness of the samples. The results
 are shown in the tables.
 Insulation Resistance (R25)
 The specific resistance at 25.degree. C. was measured for the disk-shaped
 samples. The specific resistance was measured by an insulator resistance
 meter (R8340A(50V-1 minute value) made by Advantest Co.). The results are
 shown in the tables.
 Temperature Characteristic of Capacity
 The capacity of samples of capacitors having a thickness of the dielectric
 layers of 10 .mu.m was measured in a temperature range of -55 to
 160.degree. C. to investigate if the X8R characteristic was satisfied.
 Samples which satisfied it are shown in the tables by "O" and samples not
 satisfying them by "X". Further, samples containing Yb were selected as
 examples of the present invention, while samples containing Y and samples
 not containing a rare earth element were selected as comparative examples.
 The capacity-temperature characteristics of these samples at -55.degree.
 C. to 160.degree. C. are shown in FIG. 2. FIG. 2 also shows the short
 scope satisfying the X8R characteristic. Note that for the measurement, an
 LCR meter was used and the measurement voltage was made 1V.
 X-Ray Diffraction
 Disk-shaped samples were measured by a powder X-ray (Cu--K.alpha.--ray)
 diffraction apapratus between 2.theta.=44 to 46.degree. under the
 following conditions to measure the half width of the pseudo cubic peak
 comprised of the (002) peak and (200) peak superposed. The samples with a
 half width of not less than 0.3.degree. were indicated in the tables as
 "O" and samples with ones less than 0.3.degree. as "X". Further, the
 intensity I(002) of the (002) peak and the intensity I(200) of the (200)
 peak were measured to investigate if I(002).gtoreq.I(200) was satisfied.
 Samples which satisfied it were indicated in the tables as "O" and those
 not satisfying it as "X". Note that the measurement was conducted at room
 temperature.
 X-ray generation conditions: 40 kV-40 mA
 Scan width: 0.01.degree.
 Scan rate: 0.05.degree. /minute
 X-ray detection conditions
 Parallel slits: 0.5.degree.
 Dispersion slits: 0.5.degree.
 Light receiving slits: 0.15 mm
 Note that when finding the half width, the data was divided into that for
 the K.alpha.1rays and that for the K.alpha.2 rays and the data for the
 K.alpha.1 rays used. The X-ray diffraction charts of the samples
 containing Tm and containing Y among those sample, shown in the tables are
 shown in FIG. 3 and FIG. 4. Note that these figures show also compositions
 not containing rare earth elements.
 IR Lifetime under Direct Current Electric Field
 Samples of capacitors having the compositions shown in Table 1 to Table 4
 and having a thickness of the dielectric layers of 10 .mu.m were subjected
 to acceleration tests at 200.degree. C. under a field of 10 V/.mu.m. The
 time until the insulation resistance fell below 1 M.OMEGA. was made the
 lifetime. The results are shown in Table 1 to Table 4. Note that a sample
 having a composition not containing the fourth subcomponent was also
 measured. The results are shown in Table 2.
 TABLE 1
 2.sup.nd Subcomponent: (Ba.sub.0.6,Ca.sub.0.4)SiO.sub.3,
 3rd Subcomponent: V.sub.2 O.sub.5, 6th Subcomponent: MnO
 Subcomponents Sinter
 X-ray dif. IR
 Comp. 1st 2nd 3rd 4th 6th temp.
 tan .delta. R25 X8R Half Int. life
 No. Type (mol) (mol) (mol) Type (mol) (mol)
 (.degree. C.) .epsilon. r (%) (.OMEGA. cm) char. width ratio (hr)
 101 (Comp.E) MgO 2.06 3.0 0.01 -- --* 0.374 1280 2912
 0.68 7.64 .times. 10.sup.12 x x x 1.1
 102 (Comp.E) MgO 2.06 3.0 0.01 Er 0.20* 0.374 1280
 3038 0.70 7.05 .times. 10.sup.12 x x x 16.5
 103 (Comp.E) MgO 2.06 3.0 0.01 Tm 0.20* 0.374 1280
 3086 0.70 7.04 .times. 10.sup.12 x x x 10.3
 104 (Comp.E) MgO 2.06 3.0 0.01 Yb 0.20* 0.374 1280
 3080 0.69 7.90 .times. 10.sup.12 x x x 6.2
 105 (Comp.E) MgO 2.06 3.0 0.01 Lu 0.20* 0.374 1280
 3044 0.63 8.63 .times. 10.sup.12 x x x 0.5
 106 MgO 2.06 3.0 0.01 Er 1.00 0.374 1280
 2592 0.53 1.44 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 33.5
 107 MgO 2.06 3.0 0.01 Tm 1.00 0.374 1280
 2544 0.48 1.48 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 21.3
 108 MgO 2.06 3.0 0.01 Yb 1.00 0.374 1280
 2458 0.52 1.48 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 8.0
 109 MgO 2.06 3.0 0.01 Lu 1.00 0.374 1280
 2569 0.51 1.57 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 4.0
 110 MgO 2.06 3.0 0.01 Sc 1.00 0.374 1280
 3068 0.49 8.07 .times. 10.sup.12 .smallcircle. .smallcircle.
 .smallcircle. 2.0
 111 MgO 2.06 3.0 0.01 Er 2.00 0.374 1280
 2431 0.51 1.15 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 42.0
 112 MgO 2.06 3.0 0.01 Tm 2.00 0.374 1280
 2500 0.48 1.34 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 31.5
 113 MgO 2.06 3.0 0.01 Yb 2.00 0.374 1280
 2455 0.49 1.55 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 10.0
 114 MgO 2.06 3.0 0.01 Lu 2.00 0.374 1280
 2479 0.49 1.08 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 4.9
 115 MgO 2.06 3.0 0.01 Sc 2.00 0.375 1340
 2201 1.40 2.55 .times. 10.sup.11 .smallcircle. .smallcircle.
 .smallcircle. 3.5
 116 MgO 2.06 3.0 0.01 Er 3.00 0.374 1280
 2355 0.54 1.61 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 83.0
 117 MgO 2.06 3.0 0.01 Tm 3.00 0.374 1280
 2192 0.47 2.41 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 38.0
 118 MgO 2.06 3.0 0.01 Yb 3.00 0.374 1280
 2149 0.46 2.16 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 9.4
 119 MgO 2.06 3.0 0.01 Lu 3.00 0.374 1280
 2088 0.46 3.15 .times. 10.sup.13 .smallcircle. .smallcircle.
 .smallcircle. 3.5
 120 MgO 2.06 3.0 0.01 Sc 3.00 3.000 1340
 2078 1.43 4.83 .times. 10.sup.11 .smallcircle. .smallcircle.
 .smallcircle. 3.0
 TABLE 2
 2.sup.nd Subcomponent: (Ba.sub.0.6,Ca.sub.0.4)SiO.sub.3,
 3.sup.rd Subcomponent: V.sub.2 O.sub.5, 6.sup.th Subcomponent: MnO
 Subcomponents Sinter
 X-ray dif. IR
 Comp. 1st 2nd 3rd 4th 6th temp.
 tan .delta. R25 X8R Half Int. life
 No. Type (mol) (mol) (mol) Type (mol) (mol) (.degree.
 C.) .epsilon. r (%) (.OMEGA. cm) char. width ratio (hr)
 101 (Comp.E) MgO 2.06 3.0 0.01 --* -- 0.374 1280 2912
 0.68 7.64 .times. 10.sup.12 x x x 0.35
 201 (Comp.E) MgO 2.06 3.0 0.01 Y* 4.26 0.374 1280 2481
 0.61 2.10 .times. 10.sup.13 x x x 240.92
 202 (Comp.E) MgO 2.06 3.0 0.01 La* 4.26 0.374 1280 --
 -- Semicond. x x x --
 203 (Comp.E) MgO 2.06 3.0 0.01 Ce* 4.26 0.374 1280 --
 -- Semicond. x x x --
 204 (Comp.E) MgO 2.06 3.0 0.01 Pr* 4.26 0.374 1280 --
 -- Semicond. x x x --
 205 (Comp.E) MgO 2.06 3.0 0.01 Sm* 4.26 0.374 1280 --
 -- Semicond. x x x --
 206 (Comp.E) MgO 2.06 3.0 0.01 Eu* 4.26 0.374 1280 2161
 1.83 3.82 .times. 10.sup.10 x x x 0
 207 (Comp.E) MgO 2.06 3.0 0.01 Gd* 4.26 0.374 1280 --
 -- 1.62 .times. 10.sup.5 x x x --