L. Eric Cross of Pennsylvania StateUniversity remembered
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L. Eric Cross of Pennsylvania State University remembered
P
rofessor L. Eric Cross passed away on December 29, 2016, at the age of 93. He was the Evan Pugh Professor Emeritus of Electrical Engineering at The Pennsylvania State University (Penn State), a member of the National Academy of Engineering, and a founding member of the Penn State Materials Research Laboratory. A world leader in the field of ferroelectrics, his contributions to the field encompassed fundamental aspects, new characterization techniques, and applications. Cross was beloved for his intelligence, vision, wit, and humanity, as well as the charm with which he shared his fascination with ferroelectrics and his newest ideas. He was an excellent mentor, and many of his students and postdoctoral researchers went on to scientific leadership positions. Cross had a long and robust scientific career. His earliest published research was in characterization of the properties of BaTiO3, including both optical response and switchable polarization. He made some of the first accurate measurements of spontaneous polarization in BaTiO3, which were found to be substantially higher than previous data, by achieving more complete switching. It was not until his work was reproduced at Bell Labs that Cross’s previously rejected paper on the subject was accepted by editors for publication with apologies. He later extended this work to NaNbO3 and KxNa1–xNbO3 (a material that is now under intense investigation as a lead-free piezoelectric material). This appears to have been his introduction to antiferroelectricity. By the 1960s, he had arrived at Penn State, where he conducted seminal work on the use of phenomenology to describe the behavior of ferroelectric materials. He developed an early model for the grain size effect on the dielectric properties of BaTiO3, initiated a long-running investigation of electrostriction, and studied
improper ferroelectric materials such as gadolinium molybdate. In the 1970s and 1980s, in collaboration with longtime colleague and close friend Robert E. Newnham, he developed piezoelectric composites and laid out the symmetry requirements for secondary ferroics. The work on composites was originally motivated by his work on sonar systems, but ultimately led to major improvements in ultrasonic imaging transducers, and is now ubiquitous in medical ultrasound systems. Cross conducted key measurements on the contributions of domain walls to dielectric and piezoelectric properties. He began an investigation into the origins of dielectric dispersion in ferroic materials. This ultimately led to major discoveries on the role of order-disorder in relaxor ferroelectric materials, as well as the Vogel–Fulcher description of the dispersion. He and his students also laid out the phenomenology of the lead zirconate titanate system—an essential means of describing the intrinsic properties of materials in the absence of single crystals. This work continues to be widely utilized and cited. His drive to ever-improved means of measuring strain and electrom
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