Phase transformation and conductivity in nanocrystal PbS under pressure

Abstract

The grain-size effect on the phase transition induced by pressure in PbS was studied by in situ high-pressure electrical resistance and synchrotron radiation x-ray powder diffraction measurements. The mean transition pressure of the B1-to-B16 phase transformation was found to be 6.3±1.3 GPa in 8±1 nm PbS while it is 3.1±0.7 GPa for 10 μm PbS. The resistivity of the B16 PbS phase decreases exponentially with pressure in both samples at ambient temperature. They follow R∝exp(−CP), where C=−0.64 GPa−1 for 10 μm PbS and C=−0.34 GPa−1 for 8±1 nm PbS. These results are discussed in terms of a decrease of energy band gap with increasing pressure.

The high-pressure ?/? phase transition in lead sulphide (PbS)

“…Two different structure types were proposed, viz. the GeS structure type (B16) with the space group Pbnm [7,8,12,13] and the closely related, but higher symmetric CrB structure type (B33) with the symmetry Cmcm [10,11]. A definitive decision between these two possibilities has not been possible until now on the basis of the experimental data available.…”

“…First structural studies under high pressure were performed using X-ray film methods [8]. Later, the compression behaviour of PbS was studied by means of highpressure energy dispersive X-ray powder diffraction (HP-EDX) up to 35 GPa [9,10,11,12,13].…”

Novel Pressure-Induced Structural Transformations of Inorganic Nanowires

“…For other nanostructured materials such as oxides, sulfides or elements, transition pressure shifts have been found to go in both directions. The majority of these nanomaterials (e.g., CdSe (Tolbert & Alivisatos, 1994;Tolbert & Alivisatos, 1995), ZnS (Jiang et al, 1999) and PbS (Jiang & Gerward, 2000)) exhibit higher transition pressures than bulk materials do and their transition pressures also increase with decreasing nanocrystal size (Tolbert & Alivisatos, 1995). However, other nanocrystal oxides, such as -Fe 2 O 3 (Jiang et al, 1998) and CeO 2 (Rekhi et al, 2001), have reduced transition pressures.…”

Investigation of Structural Phase Transition of PbS

“…The ab initio electronic study of pressure induced structural phase transition of lead sulphide has been carried out by Bencherif et al [8]. Phase transformation and conductivity in nanocrystal PbS under pressure have been investigated by Jiang et al [9]. Zhang et al investigated the elastic properties of PbS [10].…”

“…The structural high pressure behaviour of lead chalcogenides has paid considerable interest from both theoretical and experimental works [3][4][5][6][7][8][9][10]. Among these lead chalcogenides the lead sulphide PbS is useful as detector in infrared radiation.…”