Differential thermal analysis and solution growth of intermetallic compounds

Abstract

To obtain single crystals by solution growth, an exposed primary solidification surface in the appropriate, but often unknown, equilibrium alloy phase diagram is required. Furthermore, an appropriate crucible material is needed, necessary to hold the molten alloy during growth, without being attacked by it. Recently, we have used the comparison of realistic simulations with experimental differential thermal analysis (DTA) curves to address both these problems. We have found: (1) complex DTA curves can be interpreted to determine an appropriate heat treatment and starting composition for solution growth, without having to determine the underlying phase diagrams in detail. (2) DTA can facilitate identification of appropriate crucible materials. DTA can thus be used to make the procedure to obtain single crystals of a desired phase by solution growth more efficient. We will use some of the systems for which we have recently obtained single-crystalline samples using the combination of DTA and solution growth as examples. These systems are TbAl, Pr 7 Ni 2 Si 5 , and YMn 4 Al 8 .

Single crystal study of the layered heavy fermion compounds Ce2PdIn8, Ce3PdIn11, Ce2PtIn8 and Ce3PtIn11

“…Differential thermal analysis (DTA) has proven to be very helpful tool for determining the growth conditions for solution growth method of single crystals [18]. We performed differential scanning calorimetry (DSC) and DTA study of Ce-Pd-In system utilizing a SETSYS Evolution 24 instrument (SETARAM Instrumentation).…”

Determination of stoichiometry and site disorder in the complex intermetallics

“…Theoretical stoichiometric composition of Pr 6 Ni 2 Si 3 alloy was made by arc-melting and single crystals of Pr 6 Ni 2 Si 3 were grown by solution growth method [8]. Assuming no Si would occupy the Ni 2(a) site (0,0,1/4), compositions of Pr 6 Ni 1.57 Si 3 and Pr 6 Ni 1.76 Si 3 were obtained from powder and single crystal X-ray diffraction refinements, respectively.…”

“…The composition analysis of individual phase was done by energy-dispersive spectroscopy (EDS) on JEOL 7830F Scanning Auger Microprobe. An uncertainty better than ±0.5% was obtained by using single crystals of Ni-Pr-Si ternary compounds [8] as standards and through the removal of the innate oxide layer on the sample surface by ion sputtering. Thermal analyses were carried out in a Perkin-Elmer differential thermal analysis (DTA 7) allowing a maximum temperature of about 1500 • C. Thermocouples were calibrated at the transition temperature of high purity K 2 SO 4 and the melting point of Au.…”

Small sealed Ta crucible for thermal analysis of volatile metallic samples

“…It is particularly helpful in the solution growth of single crystals. 1 For a typical commercial, small-sample DTA, in this case a PerkinElmer Pyris DTA 7, the standard crucible is an open Al 2 O 3 crucible ͑PerkinElmer͒. This presents two problems, one of stability and one of volatility.…”

“…This crucible is the standard Ta crucible that we have used before. 1,3,4 A similar crucible can be made by mounting the tubing in a lathe and spinning one end closed, but this requires a skilled machinist and can thin the walls and leave a small hole at the tip.…”