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By S. Y. Mostowy, P. W. M. Shibley

"When Texas Gulf Sulphur Company discovered the Kidd Creek ore body in 1964, a crash program began almost immediately for the design and construction of a modern concentrator. It was necessary to mill two distinct ore types; one containing copper and zinc, the other lead, silver and zinc minerals. The final concentrator design was to handle 9,000 tons of ore daily in three circuits. One circuit was to treat copper-zinc and another lead-zinc ore exclusively on a permanent basis. A central circuit was designed with adequate flexibility to treat either of the above ore types in accordance with planned mining schedules. Ecstall Mining Limited, a wholly owned subsidiary, now operates the mine and concentrator complexes for Texas Gulf. The mine is located 15 miles north of Timmins and the concentrator 15 miles to the north-east along Highway 101. The ore is hauled from the mine to the concentrator over a 17-mile railroad. Initial milling operations began in November, 1966.1 - ABSTRACTThis paper deals with bulk reagent handling at the Kidd Creek concentrator. The reagent section at Kidd Creek has operated excellently since milling began in 1966. The bulk handling techniques are satisfactory. They have contributed substantially to good working conditions, economical practices and metallurgical efficiencies. The bulk handling features described should be considered in existing and proposed concentrators."

Jan 1, 1970

By M. J. Pool, with Appendix by Larry Kaufman, R. W. Krenzer

Thermodynmic properties of the Cu-Mn system have been deterrrzined in the temperature range 973" to 1273°K by measuring the vapor pressure of manganese in equilibrium with alloys of compositions varying from 0.13 to 0.91 rnole fraction manganese using the Knudsen effusion technique. Activities of manganese calculated from the measured vapor pressures show large positive deviations. Calculated heats and entropies of mixing are positive with a maximum occurring at approximately 0. 7 mole fraction manganese. ThE investigation of thermodynamic properties of binary systems involving transition metals is of considerable interest at the present time. The incomplete subvalency electron levels of transition metals lead to unusual behavior in some alloys, and considerable information can be obtained by determining the thermodynamic characteristics of these systems and relating the thermodynamic behavior to observed physical properties. The Cu-Mn system, shown in Fig. 1,' provides an example of an alloy system in which the determination of the equilibrium phase diagram and various physical properties has received considerable attention, but very little work has been done on measurement of the thermodynamic properties. Elemental copper and manganese have comparable electronegatives, atomic sizes, and cohesive energies, but differ in crystal structure. They form a continuous series of solid solutions only at high temperatures and the structure varies in a continuous manner from fcc at the copper-rich end to fct at the manganese-rich end.' The purpose of this investigation was to measure the vapor pressure of manganese over a series of Cu-Mn alloys and from these values determine the thermodynamic properties of the binary system. Vapor pressure measurements were made in the temperature range 973" to 1273"K, remaining within the solid-solution region for each alloy studied. EXPERIMENTAL PROCEDURE The relative thermodynamic properties of solid Cu-Mn alloys were determined from vapor pressure measurements by means of the Knudsen effusion tech- nique. Several discussions of the theory can be found in the literature. In the case of copper and manganese, it is assumed that manganese is the only component subliming, so the vapor pressure of manganese over the various alloys can be determined directly by measuring the weight loss of the effusion cell. This is a valid assumption since the vapor pressure of manganese is about four orders of magnitude higher than the vapor pressure of copper in the temperature region of interest. The vapor pressure of manganese over the alloys at any given temperature is then related to the weight loss of the effusion cell per unit area per unit time. An upper limit of 1.5 x 10"s has been measured for the ratio of polyatomic to monoatomic molecules for manganese vapor in equilibrium with solid manganese at 1180°K, so it was assumed that manganese vapor is monoatomic. The effusion cells, fabricated from high-purity alumina, are 26 mm high, 18 mm OD, and have a wall thickness of 1 mm. Three different sized holes of 2.03, 2.54, and 3.18 mm diam were drilled in the lids from the inside face to minimize chipping, and the lids were then slip-cast onto the cells to provide a gas-tight seal. Alumina was selected for this particular application both because of its resistance to thermal shock and reaction with manganese vapor. In the ideal case, the orifice of the effusion cell should have a knife edge so that effusion through the orifice

Jan 1, 1970

By W. C. Clarke

An empirical study of the nature of the embrittle-ment which occurs in martensitic and semiaustenitic precipitation hardening stainless steels upon exposure at temperatures of from about 550" to 875°F has been undertaken. This work was aimed at determining cazusation and means of controlling this phenomenon. A commercial copper bearing precipitation hardening alloy was used as a basic material for study. The effect of heat treatment variables was studied as was the effect of variations in analysis. It is concluded from the evidence that martensitic and semiaustenitic precipitation hardening stainless steels are subject to 885°F ernbrittlement similar to that observed in the straight chromium stainless steels. A characteristic of precipitation hardening stainless steels which has limited their use in certain applications is that they embrittle when held at temperatures in the range of from about 550" to 900°F. This is true to a more or less degree in all currently available alloys, either the basically martensitic type or the semiaustenitic type. The rate of embrittlement varies markedly with exposure temperature, being low at 550" to 600°F and in-creasing as the temperature increases. In spite of this embrittlement, these alloys with their unique combination of high mechanical strength, reasonable toughness, and good corrosion resistance are used in many hundreds of applications. Nevertheless, there are potential applications where the embrittle-ment described is a limiting factor. The purpose of this investigation was to study the embrittlement of these alloys and to find a way to control or eliminate it. GUIDELINES USED IN PRESENT WORK The work reported in this paper is based on a study of 17-4 PH*, a very widely used alloy. It has been used *Trademark of Armco Steel Corp., licensor. in pressurized water and boiling water atomic reactors operating at about 550°F for a number of years. As the life of such equipment is extended or operating temperatures are raised, the possibility of embrit-tlement becomes of increasing concern to materials engineers. Much investigation work was done with respect to the use of 17-4 PH at 550°F. K. C. Antony' states "Such estimation" (of an activation energy for the diffusion of chromium in iron) "would indicate W. C. CLARKE, Jr. is Senior Research Engineer, Advanced Materials Division, Armco Steel Corp., Baltimore. Md. This manuscript is based on a talk presented at the symposium on New Developments in Stainless Steel, sponsored by the IMD Corrosion Resistant Metals Committee, Detroit, Mich., October 14-15, 1968. significant secondary aging is improbable at temperatures less than 700°F within normal component service life". This statement is modified however by the recognition of the accelerating tendencies of applied stress and internal stress as well as the possible effect of irradiation. In this investigation of 17-4 PH, the H 1100 (1900°F-1 hr oil quench or air cool + 1100°F-4 hr-air cool) condition was used, partly because this condition is normally used in atomic reactors. As shown later, the precipitation hardening temperature has no real bearing on the rate of embrittlement. An exposure temperature of 800°F was selected since embrittlement at 800°F is rapid, permitting development of relative data in time periods of 400 to 500 hr. For those not familiar, a nominal present day analysis of 17-4 PH is: C Mn P S SiCrNiCuCbN 0.04 0.30 0.015 0.015 0.60 16.00 4.30 3.25 0.23 0.030 TYPICAL BEHAVIOR OF 17-4 PH Figs. 1 and 2 show the behavior of a commercial heat of 17-4 PH under the conditions defined. Characteristically, 800°F exposure causes a rapid drop in Charpy V-notch impact strength. Tensile and yield strengths gradually increase and a gradual loss of elongation and reduction of area occur, accompanied by an increase in hardness. Notched tensile strength increases to 125 hr exposure and then sharply decreases after exposure for 500 hr. The notched vs un-notched tensile ratio remains virtually constant to exposure for 125 hr (1.67 to 1.56) but drops to 1.15 after 500 hr. Tensile ductility is not alarmingly affected even after much longer exposure times than these. For example, samples aged at 1100°F for 1 hr exposed at 800°F for 4000 hr showed a drop in elonga-tion of from 13 to 11 pct and in reduction of area of from 58 to 37 pct. Notched impact is the property SmIgth KSI 3JJ[/__________^UTS-Nrteh 260 ;/- 240 —^ 200 UTS-Smooth________._, o ioo mo Sob" m Too Hours Exposure Fig. 1—Effect of exposure at 800°F for various times on notched tensile strength and smooth tensile and 0.2 pct yield strength of 17-4 PH in the H 1100 condition.

Jan 1, 1970

By Sanders GJ

Coals from the Southern Coalfield of New South Wales treated in the Port Kembla coal preparation plants of Australian Iron and Steel Pty Ltd differ substantially in their characteristics. Knowledge of, performance not only enables comparison and promotes better control, but also provides the means for predicting results. Evaluation of performance of cleaning equipment has been made in terms of probable error (Ep.) Results for Baum jigs, a Chance cone, heavy medium cyclones and water washing cyclones are examined. The efficiency factors derived from the probable error are applied to the float and sink analysis, mathematically simulating operating conditions. This method is applied to the Balgownie seam. The Balgownie seam lies between the Bulli and Wongawilli seams in the Coal measures of the South Coast and mining on a large scale began recently in the Bulli area. It is known locally as the Four Foot seam and exhibits er difficult washability characteristics, due to a comparatively high middlings content. These properties and the tively high inherent ash make careful selection of cleaning equipment essential for optimum recovery. The prediction technique is used to determine the possible results when this coal is cleaned in the Port Kembla plants. Predicted values are compared with results from full scale trial washings demonstrating the validity and accuracy of the technique. Applications of result forecasting are listed.

Jan 1, 1970

By Marcel Vallee, Fernand Dubuc

"The St-Honoré carbonatite complex, located 8 miles north of Chicoutimi, Quebec, was discovered in September 1967 as abnormal radioactivity was detected in the course of SOQUEM's aerial surveys. The complex, covered by a shallow layer of Trenton limestone, has been explored by aeromagnetic, ground gravimetric and magnetic surveys, and 12,013 feet of diamond drilling. Its age, from potassium-argon dating, is 650 million years. The carbonatite is approximately kidney-shaped and has a surface area of 6 square miles, 20 per cent of which is explored. It shows a central core of coarse-grained massive dolomitic carbonatite and an outer ring of foliated dolomitic carbonatite.The exploration work to date has resulted in the discovery, in the foliated carbonatite, of an incompletely drilled niobium (columbium) zone of pyrochlore-bearing carbonatite, at least 1,000 by 800 feet in size. This zone contains 5,000 tons per vertical foot grading 0.86 per cent Nb205 or at least 15,000 tons per vertical foot grading 0.66 per cent Nb205 or 45,000 tons grading 0.48 per cent Nb20s. The pyrochlore contains an average of 64 per cent Nb,Os. The central core contains a zone of rare-earth-bearing carbonatite (as monazite), grading up to 4.5 per cent rare-earth oxide, 3,500 ppm zinc and 290 ppm molybdenum. Stocks of nepheline syenite and magnetite diorite accompany the carbonatite. The total analysis and trace-element contents of typical rocks are presented."

Jan 1, 1970

By Norman Yarborough

Much has been written about the energy fuels including their standing with respect to reserves, their delivered Btu costs, their potential in the electrical generating market and their capabilities to meet a burgeoning demand. Yet, when all factors are placed in their proper perspective, the spiraling electrical energy market alone should guarantee each fuel a better than average market for the foreseeable future. In fact, a study made by the U.S. Federal Power Commission on the spare capacity utilities have on hand indicated that 39 of the 181 major utility systems had less than 10% reserves on hand at the end of 1969. Fuel supplies are critically low in some areas, especially in the Southeast, South Central and Midwest areas of the U.S. In other systems equipment shortages resulting from faulty equipment or delays in getting new equipment deliveries causes power failures during peak loads. In addition, lack of labor curtails the erection of some new facilities and prevents many other facilities from operating at capacity.

Jan 1, 1970

By H. B. Muller

Single stage autogenous grinding of run-of-mine ore was selected by Broken Hill South Ltd., parent Company of Cobar Mines Pty. Ltd. for the concentrator to treat 60,000 tons per four weekly period of copper and complex copper-lead-zinc sulphide ores from the C.S.A. Mine at Cobar, Australia. Ore is mined by mechanised horizontal cut-and-fill stoping and is prepared for grinding by crushing under- ground in a 60 in. x 48 in. jaw-crusher set at 5 in. closed side setting. The ore is reduced to 80% minus 76 microns in two parallel sections each of one 22 ft. dim. x 7 ft. long autogenous grinding mill, powered by a 1,250 H.P. motor, operating in closed circuit with a single stage 20 in. dim. cyclone. Broken Hill South's original concept of the concentrator required the maximum use of reliable instrumentation, centralised control, and the minimum of manning. To achieve this objective the control room, housing the process recorders, alarms, closed circuit television monitors and all the control equipment, overlooks the grinding and flotation sections, and the whole plant is serviced by a public address system. The grinding units and associated equipment are located in the open and are serviced with the aid of a mobile crane and a mobile hydraulically-operated liner lifting device.

Jan 1, 1970

By Fun-Den Wang

A new approach for evaluating pit slope stability by the limiting equilibrium method has been developed by the Bureau of Mines. The finite element method of plane strain analysis is used to find the stress field of the pit slope structure. This stress field is then used to find the normal and shear stresses along a potential failure surface. The normal stresses are used with the Coulomb equation to calculate the shear resistance. The shear stresses are integrated to determine the total driving force. The factor of safety is evaluated from the ratio of the resisting force to the driving force along a failure surface, and is found to be affected by the elastic material properties, modulus of elasticity, and Poisson's ratio.

Jan 1, 1970

By R. R. Hart, B. C. Wonsiewicz, G. Y. Chin

In recent years there has been increased miniaturization of electromechanical devices to keep pace with current trends toward smaller electronic components. A major problem facing the designer, however, is the higher stresses encountered by the material as a result of shorter springs. Hence an improvement in the elastic limit, as approximated by the 0.01 pct offset yield strength, would be highly desirable. An increase of 25 pct in the yield strength, for example, will permit a 20 pct reduction in both the length and thickness of a cantilever-type spring while maintaining the same compliance. One technique of improving the yield strength that has received little commercial attention is crystal-lographic texture strengthening.1,2 Texture strengthening is expected to be most beneficial in materials of hcp structure, but considerable gain can also be expected in cubic materials. A wire with a (111) fiber texture, for example, is expected to be 20 pct stronger than randomly oriented material, and 50 pct stronger than wire with a (100) fiber texture.293 For sheet specimens with a {110}(112) texture, characteristic of many heavily rolled fcc alloys, the (111) transverse direction is expected to be the maximum yield strength direction, about 20 pct higher than that in the (112) rolling direction.' In addition, the (111) direction is the direction of maximum modulus of elasticity for most cubic alloys. A large value of the elastic modulus could be desirable in designs where stiffer springs are required. To test the above idea, a 0.090 in. (-2.3 mm) thick commercial grade A (5 pct Sn) phosphor bronze sheet, a widely-used material for relay springs, was rolled from the spring-tempered condition (60.5 pct reduction) to various additional reductions up to a total reduction of 95 pct. Subsequently, additional material was obtained with a total thickness reduction of 97.3 pct Standard tensile specimens were prepared from the sheet material with the tensile axis parallel to and at 90 deg to the rolling direction. Tests were run on an Instron testing machine at a strain rate of about 0.050 min-l. Textures were determined by the use of the reflection pole-figure technique. Data were obtained using nickel-filtered CuKa radiation and with the aid of a Siemens pole figure goniometer. The X-ray pole figure studies show an incrzasing development of the texture toward the {110}(112) ideal

Jan 1, 1970

AN intermetallic compound, Ni3A1, has an ordered fcc structure of type Ll2, and shows peculiar dependence of the yield stress upon temperature; i.e., the yield stress increases by a factor of six upon raising the temperature from 77" to 900K1, 2 This compound is technologically important, since many nickel-base superalloys owe their high-temperature strength to the peculiar yield stress behavior of Ni3Al. The only study of the elastic behavior of this compound was made by Davies and Stoloff,1 who determined Young's modulus of poly crystalline Ni3A1 between 300" and 730°K. The determination of single-crystal elastic constants of Ni3A1 is therefore of interest in connection with dislocation dynamics and is reported in this paper. A single-crystal specimen, 1 by 1 by 3 cm, was cut from an ingot generously supplied by Dr. B. H. Kear of Pratt & Whitney Aircraft. Following initial machining with a Servomet and a surface grinder, the specimen was etched and annealed at 1100°C for 5 hr in vacuum followed by furnace cooling. Two parallel faces were oriented normal to within ±l deg of a [I101 crystallographic axis by the back-reflection Laue technique. The parallel faces were hand-lapped, etched, and polished by the usual metallographic procedures. Final thickness along the [I101 axis was (0.9325 * 0.0005) cm. Chemical analysis gave an average composition of 87.35 pct Ni. Total impurity content is esimated to be no more than 0.1 pct. The elastic constants were calculated from measurements of ultrasonic waves which were propagated along the [110] axis. A longitudinal wave and two shear waves whose displacements are aligned along the [ 110], [li~], and [001] directions, respectively, are necessary in order to completely specify the three elastic constants. Two 3/6-in. quartz transducers were bonded to the parallel faces of the sample with ~ac-seal.3 Although this bond was sensitive to thermal shock, it performed satisfactorily over the entire temperature range for both longitudinal and shear wave propagation. A frequency of 5 mHz was employed in the method of Williams and Lamb4 in order to measure the absolute value of the ultrasonic velocity. The pulse-overlap technique of Mcskimin5 was also used at this frequency in order to determine the shift in the ultrasonic velocity

Jan 1, 1970

By Bruce A. Kennedy

The place of the young engineer in the mining industry has been the subject of a large number of keynote addresses, magazine articles, and papers in the past year. One of the best of these was the keynote address given by Mr. J. C. Kinnear, Jr. at the Fifth Annual Intermountain Minerals Conference in Vail. Colorado. Mr. Kinnear presented as part of his address the statistics of a Canadian survey Instigated to find out why young engineers and geologists are leaving the mining industry. The results of the survey showed four main reasons for leaving: 1) insufficient money 2) slow promotion 3) lack of association with senior engineers, as well as insufficient opportunity to keep abreast of technological development 4) geographic isolation

Jan 1, 1970

By Freeman Bishop

The Bureau of Mines is working on a long-term program to completely revolutionize mining-to create a mine-systems technology that integrates the need to recover minerals at low cost under safe and healthful working conditions while protecting the environment. Everyone should be brought into the planning process preceding each new mining development, the Interior Department urges, and Assistant Secretary Hollis M. Dole seems determined to push this kind of systems approach with everything he can move.

Jan 1, 1970

By L. C. Headley

A series of exploratory tests was conducted to determine the effects of steady electric fields on fluid flow and streaming potential in narrow passages and porous media, the effects of steady electric fields on fluid interfaces, and the influence of internal voltages on fluid flow in a porous porcelain sample. Voltages greater than about 5 kilovolts were found to influence liquid droplets emanating from a capillary tube. Solutions of polyethylene oxide and polyacrylamide in water exhibited widely different behavior than that of other liquids tested. Liquid-liquid displacement tests in porous samples to determine the influence of high voltage applied to the displacing liquid on flow rates and recovery gave no significant differences. No consistently measurable effects were noted, either on flow rate or streaming potential, when an electric field was applied transverse to the direction of flow in porous media and in narrow rectangular or cylindrical channels. Experimental values of formation factor and streaming potential for a porous porcelain sample agreed qualitatively with those calculated from electrokinetic theory for ultrafine capillaries. However, the agreement for the electroviscous effect was not good.

Jan 1, 1970

By J. J. Barakso, C. Tarnocai

This paper outlines a method of testing for the mercury content of rocks, soils and plants. Techniques of sample collecting are described and the analytical procedures outlined. Examples are given of mercury determinations in two known mineralized areas in British Columbia - Copper Mountain Mines and Pacific Nickel Mines.

Jan 1, 1970

By J. E. Zeilinger

This Bureau of Mines report describes the preparation characteristics of three samples collected from the Kidney seam, in the Northern Field of the anthracite region. Removal of the sink 1.70 specific gravity material from the samples collected would result in greatly reduced ash contents at yields in excess of 90 percent. The Kidney seam, in the locations sampled, proved to be a low-ash anthracite containing an unusually high percentage of float 1.45 specific gravity material.

Jan 1, 1970

Jan 1, 1970

By A. G. Guy

In a special type of electrodiffusion experiment the entire specimen is at constant temperature. The vacancies are then created at one end of the specimen and flow to the other end where they are destroyed. The energy required to operate the corresponding sources and sinks results in a super saturation of vacancies at one end of the specimen and an under -saturation at the other end. This gradient in vacancy concentration produces a chemical-diffusion flux, J(D), of vacancies in addition to the flux, J(E), caused by the electric current. Using the experimental data of Ch. Herzig,5 it is shown that a super saturation of 1 pct can cause J(D) to be about 25 pct of J(E), and thus account for the anomalous behavior of short specimens. THERE are advantages in a phenomenological treatment as contrasted to an atomistic one. For example, there are many reactions involving the element copper that are quantitatively and usefully understood from a phenomenological viewpoint, even though electron theory is not yet able to predict whether copper should be fcc or cph.' Similarly, the lack of a complete atomic theory of vacancies need not prevent the development of a treatment based on thermodynamics and chemical kinetics. In the following discussion, models will be used for the vacancies and for the mechanisms by which they move or are created or destroyed, but the phenomenological treatments are not dependent on the details of these models. The important product of a phenomenological analysis is an equation that describes the relation among the measurable quantities determining the behavior of the system. Based on such an equation, experiments can be performed to study these quantities in detail. Eventually atomic theory will supply an adequate theoretical base for the phenomena in question. A chemical species whose chemical potential was invariant during reactions in binary and ternary systems of varying composition would indeed be an anomaly. Yet this is the role that has frequently been assigned to the vacancies in pure metals, in dilute solutions, and even in ordinary alloys. The weight of available evidence supports the view that supersatu-rations of vacancies are on the order of 1 pct in usual diffusion processes.' Although it may seem strange that such a small deviation from equilibrium could significantly affect the thermodynamic properties of the vacancies, it is well known that the driving force for an ordinary chemical reaction is the departure of the components from their equilibrium state. Similarly, the reaction of vacancies that results in the formation of pores in various types of diffusion3 can reasonably be attributed to the supersaturation of vacancies. In the present paper, it will be shown that small degrees of supersaturation can significantly affect the kinetics of the diffusion process itself. ISOTHERMAL ELECTRODIFFUSION Two different experimental techniques are convenient for studying the behavior of vacancies in a pure metal in the presence of an electric field. Gilder and Lazarus4 studied self-electrodiffusion in a gold specimen in which only the central portion was at high temperatures. In this case the significant vacancy sources operate inside the specimen in the presence of a temperature gradient. In the laboratory of Th. Heumann a method has been devised for studying self-electrodiffusion at constant temperature.5 In principle, there is then no effect of thermodiffusion. It will now be shown why in this case the significant ATungsten disks \^^ ^^ ^Gold disks^^ ^^"T>.... "TTZA ? Up Iy'7 markers ///// ////// initial plane p I y/y/y of joining \I 7//// V7//A_________I_________V//// -I 0 +I Distance from center of specimen (a) -— Direction of flow of electrons —Direction of flw of vacancies %yy} Matano I z~irkendall /%W, vy/A inlerfacej "interface ///// -} HfiK- +/ 0 Distance from center of specimen (6) Fig. 1—-Schematic illustration of the essential features of isothermal self-electrodiffusion. (a) Initial condition of specimen. (b) Condition of specimen after electrodiffusion.

Jan 1, 1970

By I. D. Shah

The Bureau of Mines investigated the sequence of principal chemical reactions taking place during the roasting of covellite (CuS). Practically all covellite is converted to digenite (Cul.SS) before oxidation to Cu20 begins. Part of the Cu2O is then converted to CuO, which in turn forms CuS04 through CuO?CuS04 as an intermediary. CuS04 and CuO'CuS04 decompose at 600° to 700° C to yield CuO and S03 (g) as final products. An overall mechanism is proposed for chemical reactions occurring at different interfaces of partially oxidized CuS pellets.

Jan 1, 1970

By Fathi Habashi

THE CHOICE of a precipitant for a certain metal ion depends, beside the economic factor. on the following factors: 1) The precipitant should be specific as far as possible so that pure precipitates can be obtained

Jan 1, 1970

By E. Miller, N. Chou, K. Komarek

The solid solubilities of the compounds PbS, PbSe, and PbTe have been determined by equilibrating single crystals with two phase alloys. The solubilities were determined by measuring the Hall coefficient of the equilibrated samples. The observed maximum deviations from stoichiometry on the lead rich and the chalcogen-rich side of the phase fields were: at. pct excess Pb at pct excess S at 850°C; PbSe--4 x 10'" at. pct excess Pb at at. pct excess at 800°C; and PbTe-2.8 x 10 4 at. pct excess Pb at 780°C, 10"1 at. pct excess Te at 720°C. The previously developed theory of retrograde solubility has been expanded to include intrinsic disorder in the compounds, and the experimental results are in agreement with the theory. THE solid solubility limits of intermetallic semiconducting compounds are of considerable interest, since many of these compounds have potential use as thermoelements in thermoelectric devices, as infrared detectors, or in semiconductor devices. The solidus curves of a significant number of these compounds have been reported to be retrograde with the maximum solid solubility occurring between the eu-tectic and the maximum melting temperatures. In a previous paper,' equations were derived which permit calculation of the maximum solid solubility of an AB compound exhibiting retrograde solubility. Derivation of these equations was based on the assumption that the compound is a nondegenerate semiconductor at the temperature under consideration, that the defects were unassociated, and that the vibrational contribution to the entropy of the compound could be evaluated by the Einstein approximation. It was shown that at the temperature of the maximum solid solubility The entropy term ASS is composed of the entropy of formation of the solid stoichiometric compound (AS$)*, and the entropy due to deviations from stoichiometric composition which is the sum of a con-figurational term (aS*), a vibrational term (AS,), and an electronic term (AS,). In the previous paper the positional entropy was evaluated considering the con- N. CHOU, Member AIME, formerly Graduate Student, New York University, N. Y., is with IBM, Yorktown Heights, N. Y. K. L. KOMAREK, Member AIME, formerly with New York University, is Professor, Department of Inorganic Chemistry, University of Vienna, Vienna, Austria. E. MI LLER, Member AIME, formerly with New York University, is Associate Professor of Mechanical Engineering, California State College at Long Beach, Calif. The paper is based on a thesis submitted by N. CHOU to the Graduate Division, School of Engineering and Science, New York University, in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Materials Science. tributions from defects arising from deviations from stoichiometric composition. The derivation is generalized in the appendix to include intrinsic disorder. The electronic entropy term is also recalculated in the appendix. Of the various semiconducting compounds, the solidus curves of Pbs,' and ~b~e,~ have been most extensively studied. The solidus of PbSe has also been determined, but the temperature of maximum solubility has not been accurately established.5129 The present investigation was undertaken to compare the experimental solid solubility data for these systems with the values predicted theoretically. Since the temperature and composition of the maximum solubility of PbSe has not been accurately determined, experimental emphasis was placed on determining the solidus curves for PbSe in the region of maximum solubility, although experiments were also performed on PbS and PbTe at several temperatures. X-ray diffraction studies were also made on carefully prepared powder samples of PbSe to determine the variation of lattice parameter with composition. EXPERIMENTAL PROCEDURE The procedure of Brebrick and Allgaier was employed for determining the solidus data. Monocrystal-

Jan 1, 1970