METHOD OF PREPARATION OF A GARNET-TYPE INORGANIC MATERIAL

Abstract

The present invention relates to a method of preparation of a garnet-type inorganic material. It also relates to the garnet-type inorganic material itself. The process comprises the following steps: (1) bringing an aqueous solution S comprising (i) a salt of zirconium, (ii) a salt of lanthanum and (iii) a salt of the element A or a precursor of an oxide of element A into contact with an aqueous solution of a basic compound, as a result of which a precipitate suspended in the reaction medium is obtained; (2) stirring the reaction medium obtained at the end of step (1) for at least 30 min; (3) bringing the precipitate obtained at the end of step (2) into contact with an additive selected in the group consisting of: anionic surfactants; nonionic surfactants; polyethylene glycols; carboxylic acids and their salts; and surfactants of the carboxymethylated fatty alcohol ethoxylate type; (4) calcining in air the precipitate recovered at the end of the previous step at a temperature which is at least 400° C.; (5) bringing into contact the product obtained at the end of step (4) with a salt of lithium; (6) calcining in air the product obtained at the end of step (5) at a temperature between 700° C. and 1100° C.; 20 the inorganic compound M comprising or consisting essentially of a garnet oxide or garnet-type oxide containing, as constituent elements, the elements Li, La, Zr and at least one element A selected in the group consisting of Al, Ga, Nb, Fe, W, Ta, or a mixture thereof.

Claims

1-35. (canceled)

36. An inorganic material M comprising a garnet oxide or garnet-type oxide containing, as constituent elements, the elements Li, La, Zr and at least one element A selected from the group consisting of Al, Ga, Nb, Fe, W, Ta, and a mixture thereof, the oxide being described by formula (I):
[Li.sub.x1La.sub.3Zr.sub.zA.sub.wO.sub.12]  (I) wherein: x1, z and w are positive real numbers; 1.20<z≤2.10; 0<w≤0.80; and x1 is derived from the electroneutrality of the oxide; and exhibiting: a ratio R50 higher than 50%, R50 being defined by:
R50(%)=(D50−D.sub.US50)/D50×100 wherein D50 and D.sub.US50 are the median diameters of distributions in volume of the diameters of a dispersion of the particles of the inorganic material M in N-methyl-2-pyrrolidone (NMP), obtained with a laser diffractometer, D.sub.US50 being measured after a treatment under ultrasound which consists of inserting an ultrasonic probe into a dispersion of 100 mg of the inorganic material M in 160 mL of NMP and in submitting the dispersion to sonication under a power of 140±10 W for 22 minutes. and/or a ratio R90 higher than 50%, R90 being defined by:
R90(%)=(D90−D.sub.US90)/D90×100 wherein D90 and D.sub.US90 correspond to the diameters of the particles for which 90% of the particles have a diameter which is less than D90 and are determined from distributions in volume of the diameters of a dispersion of the particles of the inorganic material M in N-methyl-2-pyrrolidone (NMP), obtained with a laser diffractometer, D.sub.US90 being measured after a treatment under ultrasound which consists of inserting an ultrasonic probe into a dispersion of 100 mg of the inorganic material M in 160 mL of NMP and in submitting the dispersion to sonication under a power of 140±10 W for 22 minutes.

37. An inorganic material M comprising a garnet oxide or garnet-type oxide containing, as constituent elements, the elements Li, La, Zr and at least one element A selected from the group consisting of Al, Ga, Nb, Fe, W, Ta, and a mixture thereof, the oxide being described by formula (I):
[Li.sub.x1La.sub.3Zr.sub.zA.sub.wO.sub.12]  (I) wherein: x1, z and w are positive real numbers; 1.20<z≤2.10; 0<w≤0.80; x1 is derived from the electroneutrality of the oxide; and exhibiting: a ratio R50 higher than 50%, R50 being defined by:
R50(%)=(D50−D.sub.us50)/D50×100 wherein D50 and D.sub.US50 are the median diameters of distributions in volume of the diameters of a dispersion of the particles of the inorganic material M in N-methyl-2-pyrrolidone (NMP), obtained with a laser diffractometer, D.sub.US50 being measured after a treatment under ultrasound which consists of inserting an ultrasonic probe into a dispersion of 100 mg of the inorganic material M in 160 mL of NMP and in submitting the dispersion to sonication under a power of 140±10 W for 22 minutes.

38. The inorganic material M according to claim 36 wherein the relative composition of the cations in the inorganic material M corresponds to formula:
Li.sub.x1La.sub.3Zr.sub.zA.sub.w  (II) wherein: w, x and z are positive real numbers; 1.20<z≤2.10; 0<w≤0.80; and 4.00≤x≤10.5.

39. The inorganic material M according to claim 36 wherein the relative composition of the cations in the inorganic material M corresponds to formula:
Li.sub.xLa.sub.3Zr.sub.zA1.sub.w1A2.sub.w2  (IIa) wherein: A1 is selected from the group consisting of Al, Ga, Fe or a combination thereof; A2 is selected from the group consisting of Nb, Ta or a combination thereof; w1, w2, x and z are positive real numbers; 1.20<z≤2.10; 0<w1≤0.20; 0.10<w2≤0.80; w1 and w2 being such that w=w1+w2 and w≤0.80; and 5.60≤x≤10.35.

40. The inorganic material M according to claim 36 wherein the relative composition of the cations in the inorganic material M corresponds to formula:
Li.sub.xLa.sub.3Zr.sub.zA1.sub.w1A2.sub.w2  (IIb) wherein: A1 is selected from the group consisting of Al, Ga, Fe or a combination thereof; A2 is W; w1, w2, x and z are positive real numbers; 1.20<z≤2.10; 0<w1≤0.20; 0.10<w2≤0.80; w1 and w2 being such that w=w1+w2 and w≤0.80; and 4.80≤x≤10.20.

41. The inorganic material M according to claim 36 wherein Zr is partly replaced by Hf in the oxide.

42. The inorganic material M according to claim 36 wherein the primary particles of the inorganic material M exhibit a d50 between 0.5 μm and 7.0 μm.

43. The inorganic material M according to claim 36 wherein the particles of the inorganic material M exhibt a D50 between 10.0 and 50.0 μm.

44. A process of preparation of the inorganic material M of claim 36, the process comprising the following steps: (1) bringing an aqueous solution S comprising (i) a salt of zirconium, (ii) a salt of lanthanum and (iii) a salt of the element A or a precursor of an oxide of element A into contact with an aqueous solution of a basic compound, as a result of which a precipitate suspended in the reaction medium is obtained; (2) stirring the reaction medium obtained at the end of step (1) for at least 30 min; (3) bringing the precipitate obtained at the end of step (2) into contact with an additive selected from the group consisting of: anionic surfactants; nonionic surfactants; polyethylene glycols; carboxylic acids and their salts; and surfactants of the carboxymethylated fatty alcohol ethoxylate type; (4) calcining in air the precipitate recovered at the end of the previous step at a temperature which is at least 400° C.; (5) bringing into contact the product obtained at the end of step (4) with a salt of lithium; (6) calcining in air the product obtained at the end of step (5) at a temperature between 700° C. and 1100° C.; the inorganic compound M comprising or consisting essentially of a garnet oxide or garnet-type oxide containing, as constituent elements, the elements Li, La, Zr and at least one element A selected in the group consisting of Al, Ga, Nb, Fe, W, Ta, or a mixture thereof.

45. The process according to claim 44 wherein the salt of zirconium is selected from the group of zirconium nitrate and zirconium chloride.

46. The process according to claim 44 wherein in step (2), the reaction medium is stirred for at least 30 minutes and the temperature of the reaction medium is between 50° C. and 200° C.

47. The process according to claim 44 wherein the additive is a carboxylic acid or a salt thereof.

48. The process according to claim 44 wherein the temperature of calcination in step (4) is between 400° C. and 800° C.

49. The process according to claim 44 wherein the bringing into contact of step (5) consists of impregnating the product obtained at the end of the step (4) with an aqueous solution of a salt of lithium or in mixing together the product obtained at the end of step (4) and the salt of lithium, both being in the powder form.

50. The process according to claim 44 wherein in step (6), the product obtained at the end of step (5) is first calcined in air at a temperature between 700° C. and 900° C. and then calcined in air at a temperature between 900° C. and 1100° C.

51. An inorganic material M obtainable by the process according to claim 44.

52. A composition (C) comprising: (i) the inorganic material M of claim 36; (ii) at least one electro-active compound (EAC); (iii) optionally at least one lithium ion-conducting material (LiCM) other than the inorganic material M; (iv) optionally at least one electro-conductive material (ECM); (v) optionally a lithium salt (LIS); and (vi) optionally at least one polymeric binding material (P).

53. An electrode (E) comprising: a metal substrate; directly adhered onto said metal substrate, at least one layer L made of a composition (Cof claim 52.

54. A separator (SP) comprising: the inorganic material M claim 36; optionally at least one polymeric binding material (P); optionally at least one metal salt, notably a lithium salt; and optionally at least one plasticizer.

55. Lithium ion battery comprising the inorganic material M of of claim 36.

Description

EXAMPLES

X-Ray Diffraction

[0164] The XRD diffractograms of the powders were acquired on a XRD goniometer in the Bragg Brentano geometry, with a Cu X Ray tube (Cu Kalpha wavelength of 1.5406 Å). The setup may be used in different optical configurations, i.e. with variable or fixed divergence slits, or Soller slits. A filtering device on the primary side may also be used, like a monochromator or a Bragg Brentano HD optics from Panalytical. If variable divergence slits are used, the typical illuminated area is 10 mm×10 mm. The sample holder is loaded on a spinner, rotation speed is typically 60 rpm during the acquisition. Tube settings were operating at 40 kV/30 mA for variable slits acquisition and at 45 kV/40 mA for fixed slits acquisition with incident Bragg Brentano HD optics. Acquisition step was 0.017° per step. Angular range is typically 5° to 90° in two theta or larger. Total acquisition time was typically 30 min or longer.

[0165] Rietveld refinements were performed using the pseudo-Voigt profile function of Thompson et al. (P. Thompson, D. E. Cox, J. B. Hastings, J. Appl. Cryst., 20 (1987), pp. 79-83). The cubic LLZO phase was indexed with the I a −3 d space group and reported atomic position and occupancy. The sample zero-shift, unit-cell parameters, scale factor, as well as isotropic size and micro-constraint broadening were refined in the model. The instrumental resolution function (IRF) was obtained from a well crystallized LaB.sub.6 sample.

[0166] For b/a determination, the intensities are determined on the diffractograms relative to a baseline taken over the 2θ angle range between 5.0° and 90.0°. The baseline is determined automatically using the software for analyzing the data of the diffractogram.

Determination of d50

[0167] As outlined before, d50 is obtained with a statistical analysis performed on a distribution (in number) of the diameters d of the primary particles, these diameters being determined from at least one photograph obtained by SEM (Scanning Electronic Microscopy). The scanning electron microscope must be properly aligned and adjusted according to the guidelines provided by the manufacturer. Moreover, a certified reference material may be used to check that the measured diameters are in agreement with the reality. From the cumulative particle size distribution of the diameters d, d50 is determined.

Determination of D10, D50, D90

[0168] These parameters were obtained by laser diffraction using a Malvern Mastersizer 3000. The samples are dispersed in NMP. The Mie theory is used to analyze the raw data. The following parameters were used: [0169] for the inorganic material M: refraction index of 2.15 and absorption index of 0.01; [0170] for NMP: refraction index of 1.46.
Determination of D.sub.US50 and D.sub.US90

[0171] These parameters were obtained by laser diffraction under the same conditions as disclosed above after treatment under ultrasound. The treatment under ultrasound consists in inserting an ultrasonic probe into a dispersion of 100 mg of the inorganic material M in 160 mL of NMP and in submitting the dispersion to sonication under a power of 140±10 W for 22 minutes. Use was made of an external ultrasound probe (750 W generator—Synetude Lab 750) adjusted to deliver 140±10 W. An ice bath was used to make sure that the suspension does not heat upper than 45° C. during the measurement.

[0172] The external ultrasonic probe was directly connected to the laser diffractometer so that it was possible to determine D50 and D90 over time (one measurement every 13 s, 100 measurements for the whole analysis of defragmentation of the particles). It was observed that for the inorganic materials M of the invention that D50 and D90 decreased over time and reached a plateau.

[0173] The process of the invention makes it possible to obtain other inorganic materials M of various compositions. See the examples 1-6 below.

Example 1: Preparation of an Inorganic Material M According to the Invention

[0174] The precursor is prepared with the process of the invention. A solution S is prepared by mixing 387.2 g of distilled water, 95 g of a solution of La(NO.sub.3).sub.3 (C=472.5 g/L, density d=1.7111), 69.8 g of a solution of ZrO(NO.sub.3).sub.2 (C=268.1 g/L, d=1.415), 4.03 g of Al(NO.sub.3).sub.3 previously dissolved in 8 g distilled water. Solution S is fed drop by drop in 1 hour into a tank reactor (volume of 1 L) stirred at 400 rpm and comprising 429.5 g of distilled water and 63.4 g of concentrated ammonia (28.0 wt %). The amount of ammonia used corresponds to an excess of 40% (molar ratio r=1.40). A white precipitate is formed.

[0175] After the addition, the mixture is drained from the reactor and transferred into a sealed pressurized tank (autoclave) where it is heated for 4 hours at 150° C. with a heating ramp of 2.5° C./min under stirring (150 tours/min). The mixture is then left to cool down to room temperature under stirring and is drained from the autoclave.

[0176] An organic additive (lauric acid, 40 wt % based on the final expected weight of the inorganic material) is added to the precipitate under stirring (400 tours/min). At the end of the addition, stirring is maintained for 30 minutes. The mixture is then filtrated and washed with basic water (volume of basic water: 1 L; pH around 9).

[0177] The cake is then calcined in air at 500° C. for 4 hours. The temperature of calcination of 500° C. is reached with a heating ramp of 4° C./min. The Al-doped precursor is then ground in a mortar to obtain an homogeneous product.

[0178] To obtain 5 g of the inorganic material M, 5.54 g of the Al-doped precursor are weighed (corresponding to 90.3% of oxides). A solution of lithium nitrate is prepared (3.26 g of LiNO.sub.3 dissolved in 2.0 g water). This corresponds to an excess of Li of 10.0%. The Al-doped precursor is impregnated with the aqueous solution of LiNO.sub.3 by adding dropwise the solution onto the precursor which is being stirred with a spatula. A humid cake is obtained at the end of this step. The cake is dried for 2 hours at 120° C. in a preheated stove, then ground in a mortar. The powder is then calcined in air at 900° C. for 6 h in a covered crucible made of alumina, the temperature of calcination being reached with a heating ramp of 5° C./min. The powder obtained after the calcination is then ground in a mortar. The powder is then calcined in air a second time at 1000° C. for 6 h with a heating ramp of 5° C./min and a cooling ramp of 2° C./min in a covered crucible made of alumina. The powder is ground in a mortar.

[0179] The relative composition of the cations in the inorganic material M obtained after the impregnation and calcination corresponds to Li.sub.6.44Al.sub.0.22La.sub.3Zr.sub.1.99 (determined by ICP).

Example 2: preparation of an inorganic material M according to the invention

[0180] The exact same process as described in example 1 was performed except that in step (6), only one calcination step at 800° C. for 6 h was applied. The temperature of 800° C. is reached after a heating ramp of 5° C./min.

Example 3: preparation of an inorganic material M according to the invention

[0181] The same process as described in example 1 was performed except that Ga(NO.sub.3).sub.3 was used instead of Al(NO.sub.3).sub.3 in the solution S. The relative composition of the cations in the inorganic material M obtained after the impregnation and calcination corresponds to Li.sub.6.80Al.sub.0.05Ga.sub.0.19La.sub.3Zr.sub.1.94 (determined by ICP).

Example 4: Preparation of an Inorganic Material M According to the Invention

[0182] The same process as described in example 1 was performed except that a mixture of Al(NO.sub.3).sub.3 and Ga(NO.sub.3).sub.3 was used in the solution S. The relative composition of the cations in the inorganic material M obtained after the impregnation and calcination corresponds to Li.sub.6.65Al.sub.0.13Ga.sub.0.10La.sub.3Zr.sub.1.94 (determined by ICP).

Example 5: Preparation of an Inorganic Material M According to the Invention

[0183] The precursor is prepared with the process of the invention. A solution S is prepared by mixing 393.4 g of distilled water, 95.66 g of La(NO.sub.3).sub.3 (C=472.5 g/L, density d=1.7111), 52.78 g of ZrO(NO.sub.3).sub.2 (C=268.1 g/L, d=1.415), 18.73 g of ammonium niobium oxalate represented by formula C.sub.6H.sub.4NNbO.sub.12. Solution S is fed drop by drop in 1 hour into a tank reactor (volume of 1 L) stirred at 400 rpm and comprising 428.4 g of distilled water and 64.4 g of concentrated ammonia (28.0 wt %). The amount of ammonia used corresponds to an excess of 40% (molar ratio r=1.40). A white precipitate is formed.

[0184] After the addition, the mixture is heated for 4 hours at 98° C. in the reactor under stirring (400 tours/min). The mixture is then left to cool down to room temperature overnight under stirring.

[0185] An organic additive (lauric acid, 40% of the final oxide weight expected) is added to the precipitate under stirring (400 tours/min). At the end of the addition, the stirring continues for 30 minutes. The mixture is then filtrated and washed with basic water (volume of basic water: 1 L; pH around 9).

[0186] The cake is then calcined in air at 500° C. for 4 hours. The temperature of calcination of 500° C. is reached with a heating ramp of 4° C./min. The Nb doped precursor is then ground in a mortar to obtain an homogeneous product.

[0187] To obtain 5 g of the inorganic material M, 5.58 g of the Nb doped precursor are weighed (corresponding to 89.7% of oxides). A solution of lithium nitrate is prepared (3.06 g of LiNO.sub.3 dissolved in 2.9 g water). This corresponds to an excess of Li of 10.0%. The Nb doped precursor is impregnated with the aqueous solution of LiNO.sub.3 by adding dropwise the solution onto the precursor which is being stirred with a spatula. A humid cake is obtained at the end of this step. The cake is dried for 2 hours at 110° C. in a preheated stove, then ground in a mortar. The powder is then calcined in air at 900° C. for 6 h in a covered crucible made of alumina, the temperature of calcination being reached with a heating ramp of 5° C./min. The powder is then ground in a mortar. The powder is then calcined in air a second time at 1000° C. for 6 h with a heating ramp of 5° C./min and a cooling ramp of 2° C./min in a covered crucible made of alumina. The powder is ground in a mortar. The relative composition of the cations in the inorganic material M obtained after the impregnation and calcination corresponds to Li.sub.7.00Al.sub.0.03Nb.sub.0.57La.sub.3Zr.sub.1.45 (determined by ICP).

Example 6: Preparation of an Inorganic Material M According to the Invention

[0188] The precursor is prepared with the process of the invention. A solution S is prepared by mixing 395 g of distilled water, 94.24 g of La(NO.sub.3).sub.3 (C=472.5 g/L, density d=1.7111), 69.26 g of ZrO(NO.sub.3).sub.2 (C=268.1 g/L, d=1.415), 4.39 g of Fe(NO.sub.3).sub.3. Solution S is fed drop by drop in 1 hour into a tank reactor (volume of 1 L) stirred at 400 rpm and comprising 433.8 g of distilled water and 66.2 g of concentrated ammonia (28.0 wt %). The amount of ammonia used corresponds to an excess of 40% (molar ratio r=1.40). A white precipitate is formed.

[0189] After the addition, the mixture is drained from the reactor and transferred into a sealed pressurized tank (autoclave) where it is heated for 4 hours at 150° C. with a heating ramp of 2.5° C./min under stirring (150 tours/min). The mixture is then left to cool down to room temperature under stirring and is drained from the autoclave.

[0190] An organic additive (lauric acid, 40% of the final oxide weight expected) is added to the precipitate under stirring (400 tours/min). At the end of the addition, the stirring continues for 30 minutes. The mixture is then filtrated and washed with basic water (volume of basic water: 1 L; pH around 9).

[0191] The cake is then calcined in air at 500° C. for 4 hours. The temperature of calcination of 500° C. is reached with a heating ramp of 4° C./min. The Fe doped precursor is then ground in a mortar to obtain an homogeneous product.

[0192] To obtain 5 g of the inorganic material M, 5.62 g of the Fe doped precursor are weighed (corresponding to 89.0% of oxides). A solution of lithium nitrate is prepared (2.96 g of LiN dissolved in 4.4 g water). This corresponds to an excess of Li of 10.0%. The Fe doped precursor is impregnated with the aqueous solution of LiN by adding dropwise the solution onto the precursor which is being stirred with a spatula. A humid cake is obtained at the end of this step. The cake is dried for 2 hours at 120° C. in a preheated stove, then ground in a mortar. The powder is then calcined in air at 900° C. for 6 h in a covered crucible made of alumina, the temperature of calcination being reached with a heating ramp of 5° C./min. The powder is then ground in a mortar. The powder is then calcined in air a second time at 1000° C. for 6 h with a heating ramp of 5° C./min and a cooling ramp of 2° C./min in a covered crucible made of alumina. The powder is ground in a mortar.

[0193] The relative composition of the cations in the inorganic material M obtained after the impregnation and calcination corresponds to Li.sub.6.91Al.sub.0.05Fe.sub.0.21La.sub.3Zr.sub.1.97 (determined by ICP).

Comparative Example C1: Preparation of an Inorganic Material by a Conventional Solid State Technique

[0194] The inorganic material was prepared by a conventional solid state technique. For this purpose 10.44 g Li.sub.2CO.sub.3, 9.80 g ZrO.sub.2, 19.40 g La.sub.2O.sub.3 and 0.41 g Al.sub.2O.sub.3 are mixed together using a 3D shaker with balls made of ZrO.sub.2—Y.sub.2O.sub.3 (diameter=1 cm) during 2 h. The powder/ball/air ratio is ⅓/⅓/⅓ in volume. 19.5 g of the obtained mixture is added into an alumina crucible with an alumina cover and calcined in air during 12 h at 900° C. with a heating ramp of 5° C./min and a cooling ramp of 2° C./min. The calcined powder is mixed for 2 h in the 3D shaker using the same balls in the same proportions as already disclosed. The mixture is then calcined in air at 1000° C. for 12 h with a heating ramp of 5° C./min and a cooling ramp of 2° C./min, before being mixed again for 2 h in the 3D shaker with the same balls. Finally a last calcination step at 1100° C. for 12 h with a heating ramp of 5° C./min and a cooling ramp of 2° C./min is performed before grinding to obtain the final product.

Comparative Example C2: Preparation of an Inorganic Material without Lauric Acid

[0195] The recipe used corresponds to the one described in example 1 but without any lauric acid.

TABLE-US-00001 TABLE I XRD amount d50 Laser diffraction in NMP Composition of cubic ratio (μm) D10 D50 D90 D.sub.US50 D.sub.US90 R50 R90 garnet oxide of the cations phase b/a by SEM (μm) (%) 1 Li.sub.6.38Al.sub.0.22La.sub.3Zr.sub.1.99O.sub.12 Li.sub.6.44Al.sub.0.22 >95% 0.012 2.4 12.9 35.4 67.2 7.7 15.9 78% 76% La.sub.3Zr.sub.1.99 2 Li.sub.6.55Al.sub.0.23La.sub.3Zr.sub.1.94O.sub.12 Li.sub.6.83Al.sub.0.23 0.104 0.6 7.4 30.7 111.0 3.4 14.4 89% 87% La.sub.3Zr.sub.1.94 3 Li.sub.6.52Al.sub.0.05Ga.sub.0.19La.sub.3 Li.sub.6.80Al.sub.0.05 >95% Zr.sub.1.94O.sub.12 Ga.sub.0.19La.sub.3Zr.sub.1.94 4 Li.sub.6.55Al.sub.0.13Ga.sub.0.10La.sub.3 Li.sub.6.65Al.sub.0.13 >95% 5.71 16.8 48.9 3.81 8.9 77% 82% Zr.sub.1.94 Ga.sub.0.10La.sub.3Zr.sub.1.94 5 Li.sub.6.26Al.sub.0.03Nb.sub.0.57La.sub.3 Li.sub.7.00Al.sub.0.03  95% 0.060 8.14 24.2 72.5 5.67 13.9 77% 81% Zr.sub.1.45 Nb.sub.0.57La.sub.3Zr.sub.1.45 6 Li.sub.6.34Al.sub.0.05Fe.sub.0.21La.sub.3Zr.sub.1.97 Li.sub.6.91Al.sub.0.05 >95% 0.002 14.5 34.3 138 6.03 14.2 82% 90% Fe.sub.0.21La.sub.3Zr.sub.1.97 C1 Li.sub.6.12Al.sub.0.24La.sub.3Zr.sub.2.04 Li.sub.6.46Al.sub.0.24 >95% 6.1 10.9 22.6 38.9 17.5 19.4 23% 12% La.sub.3Zr.sub.2.04 C2 Li.sub.6.40Al.sub.0.20La.sub.3Zr.sub.2.00 Li.sub.6.79Al.sub.0.20  63% La.sub.3Zr.sub.2.00