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This article reviews the research progress of measurement techniques and materials on the mechanocaloric effect over the past few decades. Mechanocaloric materials can be divided into elastocaloric and barocaloric materials depending on the applied uniaxial stress or hydrostatic pressure. Elastocaloric materials include non-magnetic shape memory alloys, polymers, and rare-earth compounds. Barocaloric materials include magnetic shape memory alloys, ferroelectric ceramics, superionic conductors, and oxyfluorides. The mechanocaloric effects of these classes of materials are systematically compared in terms of the isothermal entropy change and adiabatic temperature change. In addition to the thermal effects, other characteristics closely related to the application of mechanocaloric materials are also summarized. Finally, perspectives for further development of mechanocaloric materials in the solid-state cooling area are discussed. [ABSTRACT FROM AUTHOR]

Since the discoveries of polymeric nitrogen, named cg-N (2004), LP-N (2014), HLP-N (2019), another polymorph named black phosphorus nitrogen (BP-N) was synthesized at high-pressure-high-temperature conditions. The narrow existing pressure region and similar synthesized pressure of BP-N compared with cg-N indicate that the stable energy and enthalpy of formation of these two structures are close to each other, which was confirmed by our theoretical calculation. In order to obtain the pressure region of BP-N phase, pure N2 and TiN/Pb + N2 precursors were used for laser-heating high pressure experiments in diamond anvil cell (DAC), and the phase identity was examined by Raman and XRD mapping. BP-N can be synthesized in the pressure range of 130 GPa to 140 GPa with the assistance of heating absorber. With the decrease of the pressure, BP-N can be quenched to ∼ 40 GPa. The synthesizing pressure–temperature and the stable pressure region of BP-N are important for further exploration of BP-N and its kinetic and thermal dynamic relationship with other polymeric nitrogen, especially cg-N. [ABSTRACT FROM AUTHOR]