Bulk Modulus and Structural Phase Transitions of Wurtzite CoO Nanocrystals

Abstract

High-pressure behaviors of wurtzite-type hexagonal CoO nanocrystals were investigated by in situ highpressure synchrotron radiation X-ray diffraction measurements up to 57.4 GPa at ambient temperature. It is found that bulk modulus of the hexagonal CoO phase is about 115 GPa at zero pressure. During compression, the hexagonal CoO phase transfers into rocksalt-type cubic phase in the pressure range of 0.8-6.9 GPa. The volume collapse accompanied by the transition was estimated to be about 20%. This is irreversibly phase transformation; that is, the cubic CoO phase remains after pressure release. Based on the data of peak width vs pressure, a cubic-to-rhombohedral phase transition was detected for the nanocrystalline cubic CoO phase with the transition pressure of about 36 GPa, lower than 43 GPa for bulk cubic CoO phase. The bulk modulus of the nanocrystalline cubic CoO phase of about 258 GPa is larger than 180 GPa for the corresponding bulk cubic CoO phase.

Study of semiconducting nanomaterials under pressure

“…6a. The estimated relative volume collapse for B4 → B1 transition is 20.15% (at P T 06.93 GPa) which is quite close to the experimental value of 20% [15]. The pressure dependence of bulk modulus in ground and high pressure phases has been depicted in Fig.…”

“…The pressure induced structural phase transition has been observed experimentally in some semiconducting nanomaterials : ZnO (nanorods), ZnS (2.8, 5, 10 and 25.3 nm), ZnSe (nanoribbons), GaN (2-8 nm), CdSe (4.2 nm), CoO (50 nm), CeO 2 (9-15 nm), SnO 2 (3, 8, 14 nm), SiC (20,30,50, and 130 nm), c-BC 2 N (5-8 nm) and β-Ga 2 O 3 (14.8 ±1.9 nm), using in-situ energy dispersive X-ray diffraction at room temperature [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The high pressure behavior of two samples of ZnO nanorods with different grain sizes (sample A : diameter 150 nm, length 12000 nm and sample B : diameter 10 nm, length 230 nm) have been studied and compared with their corresponding bulk phase by Xiang et al [6].…”

“…The B4 to B1 structural phase transition from has been studied in both nano (0.2-0.8 nm) and bulk phases of wide band gap semiconductor GaN [13,14]. It is observed by in-situ synchrotron radiation X-ray diffraction that CoO (50 nm) nanocrystal stabilizes in B4 phase at ambient conditions and transforms to B1 phase under pressure [15]. The effect of size on stability of CdSe nanocrystal (4.2 nm) under high pressures has been investigated by X-ray diffraction and optical absorption techniques [16].…”

Facile synthesis, characterization and electrochemical properties of cuspate deltoid CoO crystallites

“…Risbud et al [11] used the thermolytic decomposition of Co(acac) 2 in refluxing benzyl ether to obtain CoO with fcc-Co phase while decomposition of Co(acac) 3 (acac = acetylacetonate) in oleylamine was also applied to synthesize wurtzite CoO [12]. Moreover, different CoO nanocrystals, such as nanoparticles [13][14][15][16], nanorod [17], nanoplatelet [18] have also been reported. However, to our best knowledge, there is no report on the preparation of pure cuspate deltoid CoO crystallites by decomposition of Co 3 O 4 under molten salt atmosphere.…”

Chemical Approach to a New Crystal Structure: Phase Control of Manganese Oxide on a Carbon Sphere Template

“…It might be underestimated because there is no consideration given to stress. [34] Alivisatos et al reported that the domain size of crystalline CdSe decreases as the system undergoes subsequent transition. [35] A similar result was observed during our hexagonal to cubic transformation.…”