The etching characteristics of congruent ${\text{LiNbO}}_3$ single crystals including doped ${\text{LiNbO}}_3$ and proton-changed ${\text{LiNbO}}_3$ have been studied in reactive ion etching (RIE) and inductively coupled plasma (ICP) etching tools, using different recipes of gas mixtures. The effects of parameters including working pressure, RIE power, and ICP power are investigated and analyzed by measurement of etching depth, selectivity, uniformity, etched surface state, and sidewall profile by means of focused ion beam etching, energy-dispersive x-ray analysis, secondary ion mass spectroscopy, scanning electron microscopy, and surface profilometry. The effects of a sample carrier wafer coating have also been investigated. Optimized processes with high etching rates, good mask selectivity, and a near-vertical profile have been achieved. Ridge waveguides on proton-exchanged ${\text{LiNbO}}_3$ have been fabricated and optically measured.

The fracture and fatigue characteristics of several cemented carbide grades are investigated as a function of their microstructure. In doing so, the influence of binder chemical nature and content (Co and 76 wt.% Co-24 wt.% Ni), as well as carbide grain size on hardness, flexural strength, fracture toughness and fatigue crack growth (FCG) behavior is evaluated. Mechanical testing is combined with a detailed inspection of crack-microstructure interaction, by means of scanning electron microscopy, in order to evaluate crack-path tortuosity and to discern fracture and fatigue micromechanisms within the metallic binder. Results show that CoNi-base hardmetals exhibit slightly lower hardness but higher toughness values than Co-base grades. Meanwhile, flexural strength is found to be rather independent of the binder chemical nature. Regarding FCG behavior, experimental results indicate that: (1) FCG threshold (K-th) values for coarse-grained grades are higher than those measured for the medium-grained ones; and (2) fatigue sensitivity levels exhibited by CoNi- and Co-base cemented carbides, for a given binder mean free path, are similar. These findings are rationalized on the basis of the increasing relevance of crack deflection mechanisms as microstructure gets coarser and the evidence of similar fatigue degradation phenomena within the binder independent of its chemical nature, respectively. (C) 2014 Elsevier Ltd. All rights reserved.Peer ReviewedPostprint (published version