Pressure-induced phase-transition and improvement of the microdielectric properties in yttrium-doped SrZrO3

In this study, the effect of pressure on undoped and 5% yttrium-doped SrZrO3 (SZY0 and SZY5) were conducted from the ambient condition to {\sim}25\ \text{GPa} with a diamond anvil cell. The comparison of the high-pressure Raman spectra of SZY0 and SZY5 indicate that SZY0 displays a rigid structure without any structural modification, whereas for SZY5 a structural transition at {\sim}15\ \text{GPa} is revealed. Some characteristic physical parameters such as bulk conductivities, grain boundary conductivities, Warburg diffusion coefficient, transference number and bulk relaxation frequency were determined by the high-pressure impedance spectroscopy data. An obvious discontinuous inflexion point (at {\sim}13\ \text{GPa}) for SZY5 sample is observable which was also verified the phase-transition of the Raman spectroscopy results. A mixed conduction mechanism for both SZY0 and SZY5 are coexisting for both SZY0 and SZY5 in a wide pressure range. The pressure-induced phase-transition of SZY5 would result in an inversion of conduction mechanism that is characterized by the dominant charge carriers transformation from electron to ion. The Maxwell-Wagner relaxation arising at the interfaces of grain and grain boundary indicates that Y-doping and pressure could make the ions diffusion much easier through the boundaries and finally enhance the dielectric performance of the sample. It is suggested that pressure could be a useful tool to manipulate the microstructure and dielectric performance of polycrystal through altering the grain boundary distribution.