Hydrogen-substituted garnet-type oxide, manufacturing method of sintered body and manufacturing method of hydrogen-substituted garnet-type oxide
11292729 · 2022-04-05
Assignee
Inventors
Cpc classification
C04B2235/656
CHEMISTRY; METALLURGY
C04B35/62645
CHEMISTRY; METALLURGY
C01G25/006
CHEMISTRY; METALLURGY
C04B2235/3217
CHEMISTRY; METALLURGY
C04B2235/3251
CHEMISTRY; METALLURGY
C04B2235/3208
CHEMISTRY; METALLURGY
Y02E60/10
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C04B2235/3227
CHEMISTRY; METALLURGY
C01G33/006
CHEMISTRY; METALLURGY
C01P2002/72
CHEMISTRY; METALLURGY
C04B2235/3203
CHEMISTRY; METALLURGY
International classification
Abstract
There is provided a hydrogen-substituted garnet-type oxide containing at least Li, H, La and Zr and has an amount of hydrogen a (moll unit) per one unit of a garnet-type oxide in a range of ≤1.85.
Claims
1. A hydrogen-substituted garnet-type oxide, containing at least Li, H, La and Zr and having an amount of hydrogen a (mol/unit) per one unit of a garnet-type oxide in a range of 0<a≤1.85, and the hydrogen-substituted garnet-type oxide being expressed by an elemental composition:
(Li.sub.7-a-3b+c-d, H.sub.a, M.sub.b)(La.sub.3-c, A.sub.c)(Zr.sub.2-d, T.sub.d)O.sub.12 where M denotes one or more elements out of Al, Ga and Fe; A denotes one or more elements out of Ca and Sr; and T denotes one or more elements out of Nb and Ta, wherein the amount of hydrogen a (mol/unit) per one unit of the garnet-type oxide is in the range of 0<a≤1.85, 0≤b≤0.22, 0.05≤c≤1.0, and 0≤d≤0.6.
2. The hydrogen-substituted garnet-type oxide according to claim 1, wherein the element M is Al, the element A is Ca and the element T is Nb.
3. The hydrogen-substituted garnet-type oxide according to claim 1, wherein the amount of hydrogen a (mol/unit) is in a range of 0.5≤a.
4. A manufacturing method of a sintered body including a garnet-type oxide, the manufacturing method of the sintered body comprising; a molding process of mixing a hydrogen-substituted garnet-type oxide with a Li compound having an equivalent amount of Li to an amount of hydrogen included in the hydrogen-substituted garnet-type oxide to obtain a mixture and molding the mixture to form a molded body; and a sintering process of sintering the molded body in a temperature range of not lower than 800° C. and not higher than 1200° C., so as to provide a sintered body including a garnet-type oxide that has a half-height width of not larger than 0.17 degrees with regard to 421-diffraction having a peak in a 2θ range of not smaller than 30.5 degrees and not larger than 31.0 degrees in X-ray diffraction analysis; wherein the hydrogen-substituted garnet-type oxide contains at least Li, H, La and Zr and has an amount of hydrogen a (mol/unit) per one unit of a garnet-type oxide in a range of 0<a≤1.85, and the hydrogen-substituted garnet-type oxide is expressed by an elemental composition:
(Li.sub.7-a-3b-c-d, H.sub.a, M.sub.b)(La.sub.3-c, A.sub.c)(Zr.sub.2-d, T.sub.d)O.sub.12 where M denotes one or more elements out of Al, Ga and Fe, A denotes one or more elements out of Ca and Sr, and T denotes one or more elements out of Nb and Ta, wherein the amount of hydrogen a (mol/ unit) per one unit of the garnet-type oxide is in the range of 0<a≤1.85, 0≤b≤0.22, 0.05≤c≤1.0, and 0≤d≤0.6.
5. The manufacturing method of the sintered body according to claim 4, wherein the sintered body includes the garnet-type oxide and has the half-height width of 421-diffraction in a range of not smaller than 0.08 degrees and not larger than 0.16 degrees.
6. The manufacturing method of the sintered body according to claim 4, wherein the sintered body has a relative density of not lower than 90%.
7. The manufacturing method of the sintered body according to claim 4, wherein the sintered body has a conductivity of not lower than 1.0×10.sup.−4 (S/cm) at 25° C.
8. A manufacturing method of a hydrogen-substituted garnet-type oxide, comprising: a firing process including at least a first process that uses and mixes a raw material including at least a Li compound, a La compound and a Zr compound and fires the mixed raw material in a temperature range of not lower than 650° C. and not higher than 900° C. to obtain a fired powdery substance; and a second process that adds and mixes, as appropriate, a Li compound to and with the obtained fired powdery substance to obtain a mixture and fires the mixture in a temperature range of not lower than 650° C. and not higher than 900° C. to obtain a fired powdery substance; and a hydrogen substitution process of causing the fired powdery substance obtained by the firing process to be immersed in a hydrogen-containing liquid for substitution of Li with H, so as to obtain the hydrogen-substituted garnet-type oxide according to claim 1.
9. The hydrogen-substituted garnet-type oxide according to claim 1, wherein the amount of hydrogen a (mol/unit) per one unit of the garnet-type oxide is in the range of 0.7≤a≤1.202.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1)
(2)
(3)
(4)
(5)
DESCRIPTION OF EMBODIMENTS
(6) The hydrogen-substituted garnet-type oxide The hydrogen-substituted garnet-type oxide according to the aspects of the present disclosure includes at least Li, H, La and Zr and has an amount of hydrogen a (mol/unit) per one unit of a garnet-type oxide in a range of 0<a≤1.85. One unit herein denotes one structural unit (1 mol) of Li.sub.7La.sub.3Zr.sub.2O.sub.12. This hydrogen-substituted garnet-type oxide is used as a raw material of a sintered body that is a dense body comprised of a garnet-type oxide. The hydrogen-substituted garnet-type oxide may be expressed by an elemental composition (Li.sub.7-a-3b+c-d, H.sub.a, M.sub.b)(La.sub.3-c, A.sub.c)(Zr.sub.2-d, T.sub.d)O.sub.12 (where M denotes one or more elements out of Al, Ga and Fe, A denotes one or more elements out of Ca and Sr and T denotes one or more elements out of Nb and Ta. The amount of hydrogen a (mol/unit) per one unit of the garnet-type oxide is in the range of 0<a≤1.85, 0≤b≤0.22, 0≤c≤1.0, and0≤d≤0.6). This amount of hydrogen a is preferably equal to or larger than 0.5 (mol/unit) and is more preferably equal to or larger than 0.7 (mol/unit). This amount of hydrogen a is also preferably equal to or smaller than 1.6 (mol/unit) and is more preferably equal to or smaller than 1.5 (mol/unit). The amount of hydrogen a in this range enhances the sinterability and thereby further enhances the relative density. In the hydrogen-substituted garnet-type oxide, the element M is preferably Al, the element A is preferably Ca, and the element T is preferably Nb.
(7) The Manufacturing Method of the Hydrogen-Substituted Garnet-Type Oxide
(8) A manufacturing method of the hydrogen-substituted garnet-type oxide according to another aspect of the present disclosure may include, for example, a firing process of mixing a raw material and firing the mixed raw material to obtain a fired powdery substance and a hydrogen substitution process of causing the obtained fired powdery substance to be subjected to hydrogen substitution.
(9) The firing process may include at least a first process that uses and mixes a raw material including at least a Li compound, a La compound and a Zr compound and fires the mixed raw material in a temperature range of not lower than 650° C. and not higher than 900° C. to obtain a fired powdery substance; and a second process that adds and mixes, as appropriate, a Li compound to and with the obtained fired powdery substance to obtain a mixture and fires the mixture in a temperature range of not lower than 650° C. and not higher than 900° C. to obtain a fired powdery substance. This firing process may further include a plurality of additional processes as needed basis, for example, a third process and a fourth process of further adding and mixing the Li compound to and with the fired powdery substance and firing the mixture. The Li compound included in this raw material may be, for example, lithium hydroxide, lithium carbonate or lithium oxide. Similarly, each of the La compound and the Zr compound may be provided in the form of a hydroxide, a carbonate or an oxide. The raw material may further include, for example, an added compound containing one or more elements out of Al, Ga and Fe, an added compound containing one or more elements out of Ca and Sr, and an added compound containing one or more elements out of Nb and Ta. Each of these added compounds may also be provided in the form of a hydroxide, a carbonate or or an oxide. The respective compounds of the raw material may be mixed, such as to provide a product that is expressed by an elemental composition (Li.sub.7-3b+c−d, M.sub.b)(La.sub.3-cA.sub.c)(Zr.sub.2-dT.sub.d)O.sub.12 (where M denotes one or more elements out of Al, Ga and Fe; A denotes one or more elements out of Ca and Sr; and T denotes one or more elements out of Nb and Ta, wherein 0≤b≤0.22, 0≤c≤1.0, and 0≤d≤0.6).
(10) The raw material is preferably mixed by a crushing/ mixing technique using, for example, a ball mill or a planetary mill. A more preferable technique of mixing is wet mixing in a solvent such as an alcohol. The firing process may be performed in the atmosphere. The firing temperature is preferably not lower than 650° C. to suppress the unreacted raw material from being left and is preferably not higher than 900° C. to further suppress the particles from coarsening due to a start of liquid phase sintering. This firing temperature is more preferably in a range of not lower than 700° C. and not higher than 800° C. The firing time is preferably in a range of not shorter than 12 hours and not longer than 72 hours and is more preferably in a range of not shorter than 16 hours and not longer than 48 hours. The firing time of not shorter than 12 hours further suppresses the unreacted raw material from being left. The firing time of not longer than 72 hours further reduces the energy consumption.
(11) The hydrogen substitution process causes the fired powdery substance obtained by the firing process to be immersed in a hydrogen-containing liquid, so as to substitute Li with H and provide the hydrogen-substituted garnet-type oxide described above. The hydrogen-containing liquid may be, for example, an acid solution or water. It is more preferable to use water as the hydrogen-containing liquid. A container used in the hydrogen substitution process is preferably a container having alkali resistance, for example, a container made of polytetrafluoroethylene. This is because hydrogen substitution produces LiOH. In this process, the immersion time in the immersion process of the fired powdery substance may be in a range of not shorter than 3 minutes and not longer than 30 minutes. The substitution amount of hydrogen a is adjustable by regulating this immersion time. The hydrogen substitution process may use, for example, an ultrasonic vibrator. Using the ultrasonic vibrator accelerates hydrogen substitution and shortens the time required for hydrogen substitution. The substitution amount of hydrogen a is adjustable by selecting one of a plurality of procedures of the hydrogen substitution process, i.e., a short time process without using the ultrasonic vibrator, a short time process with using the ultrasonic vibrator, a long time process without using the ultrasonic vibrator and a long time process with using the ultrasonic vibrator. The hydrogen substitution process may dry the obtained hydrogen-substituted garnet-type oxide after this immersion process and additionally perform another immersion process, in order to further increase the amount of hydrogen a. A preferable technique employed to collect the powder after the immersion process is filtration under reduced pressure by using, for example, a membrane filter. This effectively shortens the drying time. The collected powder may be dried by using a dryer. The powder of the hydrogen-substituted garnet-type oxide is obtained by the procedure described above.
(12) The Manufacturing Method of the Sintered Body
(13) A manufacturing method of a sintered body according to another aspect of the present disclosure is a manufacturing method of a sintered body including a garnet-type oxide and includes a molding process and a sintering process. The molding process mixes the hydrogen-substituted garnet-type oxide described above with a Li compound having an equivalent amount of Li to an amount of hydrogen included in the hydrogen-substituted garnet-type oxide to obtain a mixture and molds the mixture to form a molded body. Mixing an “equivalent amount” of Li herein means adding an identical molar amount of Li, but a slight difference in amount to be added is acceptable. Like the raw material of the hydrogen-substituted garnet-type oxide described above, the raw material may be mixed, such as to provide a product that is expressed by an elemental composition (Li.sub.7-3b+c-d, M.sub.b)(La.sub.3-cA.sub.c)(Zr.sub.2-dT.sub.d)O.sub.12 (where M denotes one or more elements out of Al, Ga and Fe; A denotes one or more elements out of Ca and Sr; and T denotes one or more elements out of Nb and Ta, wherein 0≤b≤0.22, 0≤c≤1.0, and0≤d≤0.6). The raw material may further include, for example, an added compound containing one or more elements out of Al, Ga and Fe, an added compound containing one or more elements out of Ca and Sr, and an added compound containing one or more elements out of Nb and Ta, in addition to the hydrogen-substituted garnet-type oxide. A die or a mold may be used in the molding process. The amount of pressurization in the molding process may be set appropriately according to the shape and the size of the molded body and may be, for example, in a range of not lower than 1 MPa and not higher than 100 MPa or in a range of not lower than 5 MPa and not higher than 20 MPa. The shape of the molded body is not specifically limited, but the molded body may have any shape.
(14) The sintering process sinters the molded body formed by the molding process in a temperature range of not lower than 800° C. and not higher than 1200° C., so as to provide a sintered body including a garnet-type oxide that has a half-height width of not larger than 0.17 degrees with regard to 421-diffraction having a peak in a 2θ range of not smaller than 30.5 degrees and not larger than 31.0 degrees in X-ray diffraction analysis. The sintering process may be performed in the atmosphere. A pressure sintering technique (for example, HIP) may be employed for the sintering process, but the sintering process performed in the atmosphere is simpler and thereby more preferable. The firing temperature of not lower than 800° C. achieves sintering. The firing temperature of not higher than 1200° C. is preferable, since this temperature range effectively suppresses vaporization and release of Li and the like. The melting point of the garnet-type oxide is 1300° C., so that the temperature of higher than 1300° C. is undesirable.
(15) The Sintered Body
(16) The sintered body obtained by the manufacturing method described above may be expressed by an elemental composition (Li.sub.7-3b+c-d, M.sub.b)(La.sub.3-cA.sub.c)(Zr.sub.2-dT.sub.d)O.sub.12 (where M denotes one or more elements out of Al, Ga and Fe; A denotes one or more elements out of Ca and Sr; and T denotes one or more elements out of Nb and Ta, wherein 0≤b≤0.22, 0≤c≤1.0, and0≤d≤0.6). The sintered body may include hydrogen, but it is more preferable that the sintered body does not include hydrogen. This sintered body preferably has a half-height width in a range of not smaller than 0.08 degrees and not larger than 0.16 degrees with regard to 421-diffraction in X-ray diffraction analysis. The sintered body having the half-height width in this range has the further enhanced sinterability and the further increased conductivity.
(17) This sintered body preferably has a relative density of not lower than 90%. The higher relative density is more preferable. Furthermore, this sintered body preferably has a conductivity of not lower than 1.0×10.sup.−4 (S/cm) at ambient temperature (25° C.). The higher conductivity is more preferable. With regard to the garnet-type oxide containing Li, La and Zr, the electrical conductivity indicates the ion conductivity. This sintered body has ion conductivity and may thus be applied for, for example, solid electrolytes and separators.
(18)
(19) The hydrogen-substituted garnet-type oxide, the manufacturing method of the sintered body and the manufacturing method of the hydrogen-substituted garnet-type oxide described above in detail effectively enhance the sinterability and increase the conductivity. Such advantageous effects may be attributed to the following reasons. For example, when the raw material used is a hydrogen-substituted garnet-type oxide with part of Li substituted by hydrogen, densification of the sintered body is accelerated by taking advantage of element diffusion by insertion and release of hydrogen. Hydrogen substitution improves the sinterability and increases the relative density of the garnet-type oxide. Increasing the substitution amount of hydrogen, on the other hand, reduces the crystallinity and accordingly reduces the ion conductivity. The above aspects of the present disclosure optimize the crystallinity, the upper limit of the substitution amount of hydrogen and the like, based on the finding that there are correlations of the ion conductivity and the crystallinity with the substitution amount of hydrogen. Such optimization provides the high conductivity even at the decreased sintering temperature.
(20) The present disclosure is not limited to the aspects or the embodiments described above but may be implemented by any of various other aspects within the scope of the present disclosure.
EXAMPLES
(21) The following describes concrete examples of manufacturing the garnet-type oxide according to the present disclosure as Experimental Examples. Experimental Examples 1, 13, 16, 18, 19 and 21 to 26 are comparative examples, and Experimental Examples 2 to 12, 14, 15, 17 and 20 are examples according to the present disclosure.
(22) Preparation of Hydrogen-Substituted Garnet-Type Oxide
(23) (Li.sub.6.8)(La.sub.2.95Ca.sub.0.05)(Zr.sub.1.75Nb.sub.0.25)O.sub.12 (LLZ-CN) without including hydrogen was prepared in the form of solid electrolyte particles. Starting materials used were LiOH(H.sub.2O) (manufactured by Sigma-Aldrich), La(OH).sub.3 (manufactured by Kojundo Chemical Laboratory Co., Ltd.), Ca(OH).sub.2 (manufactured by Kojundo Chemical Laboratory Co., Ltd.), ZrO.sub.2 (manufactured by Kojundo Chemical Laboratory Co., Ltd.) and Nb.sub.2O.sub.5 (manufactured by Kojundo Chemical Laboratory Co., Ltd.) These starting materials were weighed to achieve a stoichiometric ratio, were mixed and were pulverized. A vessel made of zirconia and a ball made of zirconia were used for mixing and pulverization. The starting materials were mixed and pulverized in ethanol at 180 rpm for one hour and subsequently at 300 rpm for one hour by using a planetary ball mill P-6 (manufactured by Fritsch) and were further mixed and pulverized at 700 rpm for one hour by using a premium line P-7 (manufactured by Fritsch). The pulverized substance obtained after the pulverization was dried at 80° C. by a dryer. The obtained powdery substance was placed in an Au crucible and was preliminarily fired in the atmosphere at 700° C. for 48 hours. After preliminary firing, LiOH(H.sub.2O) was added to the preliminary fired powdery substance to be 10 at % excess relative to Li in the composition with a view to compensating for the loss of Li in the sintering process. The resulting mixture was then mixed and pulverized again under the same conditions as those described above and was preliminary fired again (at 700° C. for 10 hours). It was then confirmed that unreacted raw material did not remain in the powdery substance preliminarily fired twice as described above by XRD identification of a crystalline phase. The obtained powder of LLZ-CN was immersed in water for exchange between Li and H. The conditions of immersion for exchange between Li and H were: LLZ-CN was immersed in water at a ratio of 3 g of LLZ-CN to 50 mL of water and stood still at ambient temperature (around 25° C.) for 3 to 30 minutes. The substitution amount of H is controllable by regulating this standing time. For example, the substitution amount a of H was about 0.9 (mol/unit) by standing for about 3 minutes and was about 1.6 (mol/unit) by standing for about 30 minutes. When it was required to increase the the substitution amount a of H to be equal to or larger than 1.6 (mol/unit), the substitution amount a of H was increased by performing substitution again after collection of the hydrogen-substituted LLZ. The H-substituted product was collected by filtration under reduced pressure by using a membrane filter having a recovery particle size of 300 nm. A hydrogen-substituted garnet-type oxide (LLZ-HCN) was obtained by drying the collected product at 80° C. by a dryer. The powdery substance without hydrogen substitution was specified as Experimental Example 1, and the products with the increasing substitution amounts of hydrogen were used as the raw materials (hydrogen-substituted garnet-type oxides) of sintered bodies of Experimental Examples 2 to 26.
(24) Determination of H Amount
(25) The amount of hydrogen a in each of the hydrogen-substituted garnet-type oxides prepared as described above was determined by a procedure described below. The procedure loaded the H-substituted powder in a TG-DTA mass spectrometer (manufactured by Rigaku Corporation), specified a temperature range of vaporization and release of H.sub.2O (molecular weight of 18) by mass spectrometry, and determined an amount of mass decrease in the specified temperature range by thermogravimetry (TG).
(26) The specified temperature range was a range of about 350 to 450° C. The amount of hydrogen atoms (the amount of hydrogen a) included in one unit of LLZ-HCN was calculated from the mass and the molecular weight of LLZ-CN, the mass of vaporized and released water and the molecular weight of water.
(27) Production of Sintered Body
(28) LiOH(H.sub.2O) having an equivalent molar amount of Li to a molar amount of H included in LLZ-HCN prepared as described above was weighed and was dry blended with the LLZ-HCN powder. This powdery mixture was pressurized in a mold at 10 MPa for about 2 minutes, so that a molded product was obtained in the form of a pellet. The molded product in the form of a pellet was sintered in a temperature range of not lower than 800° C. and lower than 1300° C.
(29) X-Ray Diffraction Analysis
(30) The obtained sintered body was measured by X-ray diffraction analysis. An XRD apparatus smart-Lab (manufactured by Rigaku Corporation) was used for this measurement. The measurement was performed in a 20 range of 10 to 80 degrees at every 0.01-degree step by using a Cu X-ray tube. A half-height width of a diffraction peak was calculated by using analysis software manufactured by Rigaku Corporation. A function, Pearson-VII, was used for the calculation. The half-height width of a 421-diffraction peak, i.e., the maximum diffraction peak of the garnet-type oxide, was calculated.
(31) Measurement of Conductivity
(32) Au electrodes were welded to respective faces of the pellet of the sintered body produced as described above. Au paste (manufactured by Tanaka Kikinzoku Kogyo K.K) was used for the measurement. The welding temperature was 750° C., and the welding time was 30 minutes. An AC impedance analyzer 42941A (manufactured by Agilent Technologies) was used for measurement of the conductivity.
(33) Results of Discussion
(34) Table 1 summarizes the amount of hydrogen a (mol/ unit) in each of the hydrogen-substituted garnet-type oxides used as the raw materials of the sintered bodies, the half-height width (degrees) of a 421-diffraction peak of each of the sintered bodies, the conductivity (s/cm) at 25° C., the relative density (% by volume) of each of the sintered bodies.
(35) As shown in
(36) The hydrogen-substituted garnet-type oxide, the manufacturing method of the sintered body and the manufacturing method of the hydrogen-substituted garnet-type oxide of the present disclosure are not limited to the aspects or the embodiments described above but may be implemented by any of various other aspects within the scope of the present disclosure.
(37) TABLE-US-00001 TABLE 1 Industrial Applicability The aspects of the present disclosure are applicable in the technical field using substances conducting Li ion, for example, in the technical field of battery industries. SUBSTITUTION HALF-HEIGHT WIDTH OF RELATIVE AMOUNT OF H a.sup.1) 421-DIFFRACTION CONDUCTIVITY DENSITY (mol/unit) PEAK (°) (S/cm) (%) EXPERIMENTAL EX 1 0 0.093 1.52 × 10.sup.−4 75.5 EXPERIMENTAL EX 2 0.7 0.113 5.75 × 10.sup.−4 EXPERIMENTAL EX 3 0.913 0.115 3.80 × 10.sup.−4 93.5 EXPERIMENTAL EX 4 1.002 0.167 8.70 × 10.sup.−5 EXPERIMENTAL EX 5 1.013 0.123 4.27 × 10.sup.−4 EXPERIMENTAL EX 6 1.039 0.129 3.60 × 10.sup.−4 EXPERIMENTAL EX 7 1.045 0.113 3.81 × 10.sup.−4 93.8 EXPERIMENTAL EX 8 1.148 0.153 2.76 × 10.sup.−4 EXPERIMENTAL EX 9 1.202 0.123 4.69 × 10.sup.−4 92.5 EXPERIMENTAL EX 10 1.491 0.166 7.30 × 10.sup.−5 EXPERIMENTAL EX 11 1.494 0.141 2.72 × 10.sup.−4 EXPERIMENTAL EX 12 1.556 0.153 2.67 × 10.sup.−4 EXPERIMENTAL EX 13 1.603 0.255 2.32 × 10.sup.−5 EXPERIMENTAL EX 14 1.604 0.162 6.17 × 10.sup.−5 EXPERIMENTAL EX 15 1.654 0.169 4.93 × 10.sup.−5 EXPERIMENTAL EX 16 1.680 0.177 6.32 × 10.sup.−5 EXPERIMENTAL EX 17 1.711 0.143 2.69 × 10.sup.−4 91.4 EXPERIMENTAL EX 18 1.722 0.198 2.90 × 10.sup.−5 EXPERIMENTAL EX 19 1.764 0.190 1.16 × 10.sup.−5 EXPERIMENTAL EX 20 1.829 0.150 2.15 × 10.sup.−4 EXPERIMENTAL EX 21 1.866 0.192 5.04 × 10.sup.−5 91.3 EXPERIMENTAL EX 22 2.118 0.203 3.23 × 10.sup.−5 91.2 EXPERIMENTAL EX 23 2.129 0.173 4.88 × 10.sup.−5 EXPERIMENTAL EX 24 2.130 0.203 7.79 × 10.sup.−5 EXPERIMENTAL EX 25 2.327 0.173 4.88 × 10.sup.−5 EXPERIMENTAL EX 26 2.773 0.232 4.11 × 10.sup.−5 90.5 .sup.1)a value of (Li.sub.7−a−3b+c−d, H.sub.a, M.sub.b) (La.sub.3−c, A.sub.c) (Zr.sub.2−d, T.sub.d) O.sub.12