Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides

Summary

The synthesis of high quality bulk and thin film (Mg_0.25(1-x)Co_xNi_0.25(1-x)Cu_0.25(1-x)Zn_0.25(1-x))O and (Mg_0.25(1-x)Co_0.25(1-x)Ni_0.25(1-x)Cu_xZn_0.25(1-x))O entropy-stabilized oxides is presented.

Abstract

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg_0.25(1-x)Co_xNi_0.25(1-x)Cu_0.25(1-x)Zn_0.25(1-x))O (Co variant) and (Mg_0.25(1-x)Co_0.25(1-x)Ni_0.25(1-x)Cu_xZn_0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg_0.25(1-x)Co_xNi_0.25(1-x)Cu_0.25(1-x)Zn_0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg_0.25(1-x)Co_0.25(1-x)Ni_0.25(1-x)Cu_xZn_0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.

Introduction

Since the discovery of high-entropy metal alloys in 2004, high-entropy materials have attracted significant interest due to the properties such as increased hardness^1,2,3, toughness^4,5, and corrosion resistance^3,6. Recently, high-entropy oxides^7,8 and borides⁹ have been discovered, opening up a large playground for material enthusiasts. Oxides, in particular, can demonstrate use....

Protocol

Caution: Wear necessary personal protective equipment (PPE) including close-toed shoes, full length pants, safety glasses, particulate filtration mask, lab coat, and gloves as oxide powders pose a risk for skin contact irritation and eye contact irritation. Consult all relevant material safety data sheets before beginning for additional PPE requirements. Synthesis should be done with the use of engineering controls such as a fume hood.

1. Bulk Synthesis of Entropy-stabilized Oxides

1. Mass Calculation of Constituent Oxide Powders
   1. Estimate the total desired mass of the target by multiplying the desired v....

Results

X-ray diffraction (XRD) spectra were taken of both the prepared (Mg_0.25(1-x)Co_xNi_0.25(1-x)Cu_0.25(1-x)Zn_0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg_0.25(1-x)Co_0.25(1-x)Ni_0.25(1-x)Cu_xZn_0.25(1-x))O (x = 0.11, 0.27) bulk ceramics (Figure 4a) and deposited thin films (Figure 4b). These data show that the samples are single phase.......

Discussion

We have described and shown a protocol for the synthesis of bulk and high-quality, single crystalline films of (Mg_0.25(1-x)Co_xNi_0.25(1-x)Cu_0.25(1-x)Zn_0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg_0.25(1-x)Co_0.25(1-x)Ni_0.25(1-x)Cu_xZn_0.25(1-x))O (x = 0.11, 0.27) entropy-stabilized oxides. We expect these synthesis techniques to be applicable to a wide range of entropy-stabilized oxide compositions as more are discovere.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
MAGNESIUM OXIDE 99.95%	Fisher	AA1468422
COBALT(II) OXIDE, 99.995%	Fisher	AA4435414
NICKEL(II) OXIDE 99.998%	Fisher	AA1081914
COPPER(II) OXIDE 99.995%	Fisher	AA1070014
ZINC OXIDE 99.99%	Fisher	AA8781230
TRICHLROETHLENE SEMICNDTR 9	Fisher	AA39744K7
ACETONE SEMICNDTR GRD 99.5%	Fisher	AA19392K7
2-PROPANOL ACS 99.5%	Fisher	A416S4
Mineral oil, pure	Acros Organics	AC415080010
alumina crucible	MTI Corporation	eq-ca-l50w40h20
ZIRCONIA (YSZ) GRINDING MEDIA	Inframat Advanced Materials	4039GM-S010
SiC paper 320/600/800/1200	South Bay Technology	SDA08032-25
MgO (100) substrate, 5x5x0.5 mm, 1SP	MTI Corporation	MGa050505S1
OXYGEN COMPRESSED ULTRA HIGH PURITY GRADE, 99.999%	Cryogenic Gases	OXYUHP
NITROGEN COMPRESSED EXTRA DRY GRADE	Cryogenic Gases	NITEX