SOLID STATE PHASE RELATIONSHIPS in the SODIUM-POTASSIUM-ANTIMONY TERNARY SYSTEM by Carlos A, Villachica
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SOLID STATE PHASE RELATIONSHIPS IN THE SODIUM-POTASSIUM-ANTIMONY TERNARY SYSTEM By Carlos A, Villachica ProQuest Number: 10781568 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10781568 Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 T—1081 A thesis respectfully submitted to the Faculty and the Board of Trustees of the Colorado School of Mines in partial fulfillment of the requirements for the degree of Master of Science in Metallurgical Engi* neering,, Signed: f t ' CarVos. A. Vi llachica Golden, Colorado Date: May 12, 1966 Approved: Fa u T C Hero Id" Thesis Advisor iC A M / - M a ^ j l a a / A. W. SchlSriften Head of Department Golden, Colorado Date: May 12, 1966 i i T-1081 ABSTRACT The solid state phase relationships of the ternary sodium-potassium- antimony system have been studied by standard X-ray d iffraction proce dures, using pointer samples enclosed in pyrex capillary tubes. The in i tial mixtures were prepared in a specially conditioned "dry box" under dry nitrogen atmosphere. All compositions were heat treated in a Lindberg tube furnace under a protective atmosphere of purified argon gas. A set of binary alloys was prepared to check the phase relationships established by previous investigators on the two binary alloy series, Na-Sb and K-Sb. The Na-Sb alloy series was found to be well established, and the present study agrees with the work done by Mathewson(l); but in the K-Sb alloy series two more compounds were found which had been over looked by Parravano (2 ). The results Indicated that these two compounds have the formulas KSb2 and K5Sb<,« Based on the binary compounds involved in this study, a series of ternary alloys was prepared to determine the Alkemade triangles. When this study was begun, the author did not have knowledge of the existence of the compound Na2KSb previously discovered by Sommer (3) to aid in i i i T-1081 determining the Alkemade lines* A new ternary compound having a com position corresponding to the formula K2NaSb was found. Unlimited solid s o lu b ility was discovered in the fie ld between K2NaSb and K3Sb in the pseudo-binary section drawn through Na3Sb, Na2 KSb, K2NaSb and K3Sb. Consequently, this gave two two-phase regions inside of the diagram, bounded by the triangles K5Sb^-K3Sb-NaK2Sb and K3Sb-NaK2Sb-K, respectively. Since no other visib le solid s o lu b ilitie s were found, they may be con sidered negligibly small. The isothermal section of this ternary phase diagram a t room temperature showed the presence of twelve Alkemade t r i angles. The melting temperatures of the new phases found in this study were determined by thermal analysis techniques, Na2KSb melts congruently at 667°C; NaK2Sb melts congruently at 618°C; KsSb^ melts incongruently at 509°C; and KSb2 melts congruently at 409°C, iv T-1081 TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS—......................................................................... v ii LIST OF TABLES..................................................................................................... v iii LIST OF APPENDICES................................................................. ix ACKNOWLEDGMENTS ....................................................................................... - x INTRODUCTION-------------------------------------------------- 1 LITERATURE SURVEY---------------------------------------- 4 Binary Sodium-Potassiurn System— — —— —— — —— — — 4 Binary Sodium-Antimony System— — —————— —— ——— 4 Binary Potassium-Antimony System—— — ------- ————— 7 Ternary Sodium-Potassi um-Antimony System—— —— — — — 9 EXPERIMENTAL APPARATUS AND PROCEDURE --------------------------------------- 10 Experimental Apparatus— ——— — — — — — — 10 Dry Box—— ------- — — ------------— — —— — — — — 11 Gas Purification Train— — —— — ——————— 13 Alloy Heat Treatment Furnace Unit— — — 17 Melting Temperature Determination System—— ———— 19 X-ray Diffraction Unit— ——— — — ------- —— —— 19 v T-1081 Page Experimental Procedure™ 22 Preparation of the Alloys for Phase Relationship Determinati on——— ———— ———————————— 22 Preparation of Alloy Specimens for X-ray Diffraction Analysis-------------------- ———--------- • 26 Melting Temperature Determinations Procedure——— —— 27 EXPERIMENTAL RESULTS AND DISCUSSION........................................................... 29 Binary Sodium-Potassi urn System ——----------- —--------------------- 29 Binary Sodium-Antimony System-— ------—————— — ——— 30 Binary Pot as si um-Antimony System-— — - — —— ----------- 34 Discussion of the New Phases Found in the K-Sb System— 36 Ternary Sodium-Pot as si urn-Antimony System— — — ———— 38 Melting Temperature Determinations of the New Phases Found in this Study— — — —— —————— — 45 SUMMARY AND CONCLUSIONS ....................................................................... 48 APPENDIX.............................................................................- ................................. 51 LITERATURE CITED................................. - ............................................................. 74 vi T-1081 LIST OF ILLUSTRATIONS Figure Page 1, Potassium-Sodium Equilibrium Diagram— ———— ------- 5 2, Sodium-Antimony Equilibrium Diagram— --------------------- -— — 6 3« Potassi um-Antimony Equilibrium Diagram— ------------—— 8 4. Photograph of Dry Box— — ———— ------------------ 12 5. Photograph of Gas Purification Train and Heat Treatment Furnace— - —— -------------------------------------—— 15 6. Diagram of Argon Purification Train— — — --------- 16 7* Diagram of Heat Treatment Furnace Unit— — — — — — . 18 80 Photograph of Melting Temperature Determination System 20 9. Diagram of Apparatus fo r Melting Temperature Determination and Ice-Water Cold Junction for Thermocouple — — 21 10* Isothermal Section of Na-K-Sb System at Room Temperature— 42 v ii T-1081 LIST OF TABLES Table Page I* Alloy Compositions Prepared 1n the Binary Sod1um-Antimony System-——— —— —— — —— —— — —— ——— —— 31 2* Alloy Compositions Prepared in the Binary Potassium- Antimony System————— ——— ——— — —— ——— 34 3, Alloy Compositions Prepared in the Ternary Sodium- Potassi um-Antimony System———— —— — — ------ 38 v ii i T-1081 LIST OF APPENDICES Appendix Page I* Purity of Materials---------------------------------------------------------------------51 I I . Oxygen Partial Pressures 1n Argon Gas During Purification 52 III, X-Ray Powder Diffraction Data— —— — —— — — --------- 55 IV, Characteristics of Intermetallic Compounds Involved in This Study-------------- — ------- — -----------— — — — — — 70 V. Thermodynamics of Alkali Metal-Antimony System—— ——— 71 1 x T-1081 ACKNOWLEDGMENTS The author wishes to express his particular Indebtedness to Dr. Paul G. Herold, Research Professor of Ceramic and Metallurgical Engineering, for his continuous in terest and guidance throughout this study. The author also wishes to express his appreciation to the Colorado School of Mines Foundation, Incorporated, for providing a research assistanceship in connection with this investigation. Grateful acknowledgment 1s extended to Cerro de Pasco Corporation for granting the author a one-year scholarship, followed by a continued leave of absence in order that this study could be completed. X T-1081 INTRODUCTION The properties of intermetal lie compounds formed by a lk a li metals and elements of the V-A group of the periodic system, have been studied for various reasons. Zintl and co-workers (4) investigated these com pounds to clarify their crystal chemistry, and in particular to deter mine the boundary at which the transition of the type of bonding of alloys from m etallic to ionic takes place. In 1936 Gorlich (5) discovered the excellent photoemissivity of Cs3Sb. Since then, many semi-conducting photoemissive materials have been found. These materials have the characteristic of being interme- t a llic compounds of a lk a li metals with metals of the IVth, Vth, or Vlth group of the periodic system. In a ll compounds containing a single a lk a li metal, the threshold wavelength increases with the atomic number of the a lk a li metal involved, so that the cesium compound is always the most sensitive to visible radiation. The Sb-Cs cathode is outstanding among these materials because i t has high photosensitivity, is simple to produce, and has been the sub ject of numerous experimental studies aimed at a better understanding of the photoelectric mechanism. T-1081 2 The excellent performance of the Sb-Cs photocathode indicated that the material should have a well-defined chemical composition* Quantita tive studies by Sommer (6 ) suggested the stoichiometric formula Cs 3Sb. Jack and Wachtel (7) determined the crystal structure of Cs3Sb and found it had a partially ordered structure based upon the B32 sodium thallide type* They also attempted to correlate the photoelectric properties of the compound with the crystal structure* Although cesium is superior to other a lk ali metals in a ll types of cathodes, Sommer (3) found that the combination of two or more alkali metals with