No abstract

Impedance spectroscopy (IS) was used to measure electrical responses of various plasma‐sprayed yttria‐stabilized zirconia (YSZ) materials. Coupled with X‐ray diffraction, scanning electron microscopy, and microindentation, the effects of heat treatment on microstructure, phase composition, and mechanical properties were investigated. Results showed electrical responses for YSZ grains and grain boundaries varied with size and position of silver electrodes used. YSZ heat treated at 950°C showed micro‐crack closure: at 1150°C, microstructural and phase changes, and at 1450°C, formation of a resistive monoclinic phase. The aim was to develop that IS as a non‐destructive tool for thermal barrier coatings; results suggest IS can monitor microstructural and phase changes in YSZ under certain conditions.

High-throughput synthesis of the ferroelectric solid solution Pb(Zr1−xTix)O3 (PZT) on single Pt∕Ti∕SiO2∕Si substrates was demonstrated using a modified molecular beam epitaxy (MBE) system. The PZT films exhibited a phase transition from rhombohehdral to tetragonal symmetry as a function of Zr:Ti ratio, across the substrate diagonal. This was consistent with the presence of a morphotropic phase boundary at Zr:Ti ratio of 0.64:0.36, different from the value of 0.53:0.47 observed for bulk ceramics. All points on the films exhibited ferroelectric hysteresis. Results demonstrate the feasibility of high-throughput MBE for deposition of complex ferroelectric oxides, and pave the way for further materials discovery.

Synthesis of Pb(Zr 1-x Ti x )O 3 (PZT) on a single substrate using a high-throughput molecular-beam epitaxy technique was demonstrated. In situ synthesis of crystalline PZT at elevated substrate temperatures could not be achieved, as reevaporation of Pb (PbO) occurred and the partial pressure of O 2 was insufficient to prevent formation of a PbPt x phase during deposition. Instead, ex situ postdeposition annealing was performed on PZT deposited at room temperature. Dense single phase PZT was prepared with a compositional range of 0.1 > x > 0.9, for film thicknesses up to 800 nm. Transmission electron microscopy revealed the grain size increased from 50 nm to $0.5 mm with increasing Zr-concentration and became more columnar. Raman, x-ray diffraction, and scanning electron microscopy/energy dispersive spectroscopy results revealed a morphotropic phase boundary between rhombohedral and tetragonal phases occurred at x $0.4 rather than at x = 0.47 in bulk ceramics. This was attributed to clamping arising from mismatch in thermal expansion between the film and substrate.