Minli Shi

Mechanical properties anisotropy of PZNT93/7 single crystal

The mechanical properties of 93%Pb(Zn1/3Nb2/3)O3–7%PbTiO3 (PZNT93/7) single crystal were evaluated by microindentation and nanoindentation techniques. The (1 1 1) facet of the crystal exhibited excellent combination mechanical properties (Vickers microhardness Hv, fracture toughness Kc and elastic modulus Er) than those of (0 0 1) facet. The Hv on (1 1 1) and (0 0 1) facets were 3.71 GPa and 3.00 GPa, respectively. In-plane fracture toughness anisotropy was observed on both the (1 1 1) and (0 0 1) facets, the Kc value was low in the direction parallel to the domain wall but large in the direction perpendicular to it. The Er of (0 0 1) and (1 1 1) facets was independent of the load, Er(1 1 1) was measured to be about 130 GPa and Er(0 0 1) was about 110 GPa. The above results implied that (0 0 1) PZNT crystals would face a more severe challenge in device application due to their weaker combination mechanical properties but outstanding piezoelectric properties than those of (1 1 1) PZNT crystals.

Phase transitions and optical properties in 〈001〉 (1−x)PbZn1/3Nb2/3O3−xPbTiO3 single crystals

The effect of a constant electric field (0 < E < 5 kV/cm) on the optical properties of PbZn1/3Nb2/3O3−xPbTiO3 (PZN-xPT) crystals with x = 7 and 9% has been analyzed. It has been shown that, at temperatures close to the temperature of the transition from the rhombohedral [R(X)] phase to the tetragonal (T) phase, two induced phase transitions are observed in the electric field, which are associated with the appearance of new intermediate phases Ma and Mc [R(X)-Ma-Mc-T]. Correlation between these two transitions and the PbTiO3 content x has been found. The E-T phase diagrams have been obtained. The Mc phase in PZN-9PT crystals is found to remain the ground state after the removal of the electric field, whereas the Mc phase in PZN-7PT crystals is metastable and is transformed into the Ma phase after the removal of the electric field.

Optical properties of (1 - x)PbZn1/3Nb2/3O3-xPbTiO3 single crystals

The temperature dependence of the optical transmission and small-angle light scattering with and without applied constant electric field was studied in relaxor single crystals of 0.91PbZn1/3Nb2/3O3-0.09PbTiO3 (PZN-PT 91/9) and 0.93PbZn1/3Nb2/3O3-0.07PbTiO3 (PZN-PT 93/7) solid solutions in the region of two phase transitions: (i) from cubic paraelectric to tetragonal ferroelectric phase at T=Tc and (ii) from tetragonal ferroelectric to rhombohedral ferroelectric phase at T=Trt. In the absence of external electric field, only the phase transition at Tc proceeds in both PZN-PT 91/9 and PZN-PT 93/7 crystals according to a percolation mechanism and is accompanied by the appearance of a sharp maximum in the small-angle light scattering intensity curve. In PZN-PT 93/7 crystals, the application of a relatively weak electric field induces an additional percolation type phase transition at Trt.