Method of manufacturing a clathrate compound
The present invention comprises new materials, material structures, and processes of fabrication of such that may be used in technologies involving the conversion of light to electricity and/or heat to electricity, and in optoelectronics technologies. The present invention provide for the fabrication of a clathrate compound comprising a type II clathrate lattice with atoms of silicon and germanium as a main framework forming lattice spacings within the framework, wherein the clathrate lattice follows the general formula Si 136−y Ge y , where y indicates the number of Ge atoms present in the main framework and 136−y indicates the number of Si atoms present in the main framework, and wherein y>0.
1. A method of synthesizing a clathrate compound 1, the method comprising the steps of:
a) forming an intermediate Zintl compound in a nitrogen gas atmosphere;
b) grinding the intermediate Zintl compound to a fine powder in an inert atmosphere;
c) heating the ground intermediate Zintl compound through a first temperature of approximately 360° C. at a rate of approximately several hundred ° C/min; and
d) heating the intermediate Zintl compound to a second temperature for a predetermined second duration of time to form a clathrate compound comprising a type II clathrate lattice with atoms of silicon and germanium as a main framework forming lattice spacings within the framework, wherein the clathrate lattice follows the general formula Si136−yGey, where y indicates the number of Ge atoms present in the main framework and 136−y indicates the number of Si atoms present in the main framework, and wherein y>0, wherein the second temperature determines the composition of the clathrate compound and the second duration of time determines a guest atom content within the lattice spacings of the clathrate compound.
2. The method of claim 1 , wherein the intermediate Zintl compounds are selected from the group consisting of NaSi, NaGe, NaSn, KSi, KGe, KSn, RbSi, RbGe, RbSn, CsSi, CsGe, CsSn, BaSi 2 , BaGe 2 , BaSn 2 , SrSi 2 , SrGe 2 , SrSn 2 , Na 1-x K x Si 2 , Na 1-x K x Ge 2 , Na 1-x K x Sn 2 , Na 1-x Rb x Si 2 , Na 1-x Rb x Ge 2 , Na 1-x Rb x Sn 2 , Na 1-x Cs x Si 2 , Na 1-x Cs x Ge 2 , Na 1-x Cs x Sn 2 , K 1-x Rb x Si 2 , K 1-x Rb x Ge 2 , K 1-x Rb x Sn 2 , K 1-x Cs x Si 2 , K 1-x Cs x Ge 2 , K 1-x Cs x Sn 2 , Rb 1-x Cs x Ge 2 , Rb 1-x Cs x Sn 2 , NaSi 1-y Ge y ,KSi 1-y G y , RbSi 1-y Ge y , KSi 1-y G y , RbSi 1-y Ge y , CsSi 1-y Ge y , Na 1-x Rb x Si 1-y Ge y , Na 1-x Cs x Si 1-y Ge y , K 1-x Cs x Si 1-y Ge y , and Rb 1-x Cs x Si 1-y Ge y (0<x, y<1), or any variation, combination, mixture, alloy, or solid solution of any of these compounds.
3. The method of claim 1 , wherein the intermediate Zintl compounds are formed by a reaction of appropriate high purity elements in the proper mole ratios for a predetermined time in a crucible, sealed in a steel canister under high purity nitrogen gas at a predetermined pressure.
4. The method of claim 1 , wherein the intermediate Zintl compound is NaSi, the first temperature is obtained by inserting the tube containing the compound into a tube furnace preheated to 800° C., but removing the tube before decomposition of the clathrate begins, at approximately 450° C. under vacuum, resulting in a clathrate compound of the form Na 24 Si 136 .
5. The method of claim 1 , wherein the intermediate Zintl compound is NaSi, and the second temperature is between about 360° C. and 425° C.