Structural and electronic phase transitions in Zr1.03Se2 at high pressure

We have carried out a detailed high pressure investigation using x-ray diffraction, Raman spectroscopy, and low temperature resistivity measurements on 1T ZrSe2 having an excess of 3 at.% Zr. A careful x-ray diffraction data analysis shows that the sample undergoes a gradual structural transition to a monoclinic structure, with a mixed phase in the pressure range of 5.9 GPa to 14.8 GPa. We observe a minimum in the c/a ratio as well as in the full width at half maximum of the A(1g) Raman mode at the same pressure in the parent 1T phase, which indicates an electronic phase transition. The sample shows a metallic characteristic in its low temperature resistivity data at ambient pressure, which persist until about 5.1 GPa and can be related to the presence of slight excess Zr. At and above 7.3 GPa, the sample shows a metal to semiconductor transition with the opening of a very small band gap, which increases with pressure. The low temperature resistivity data show an upturn, which flattens with the increase in pressure. The phenomenological analysis of the low temperature resistivity data indicates the presence of the Kondo effect in the sample, which may be due to the excess Zr.