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ion Moving Telecommunications Forward

Rick Ubic, Boise State University, DMR 1052788

Outcome: Researchers at University of Illinois at Urbana Champaign and Boise State University are investigating the effects of dopants and vacancies on the structure and properties of dielectric perovskite ceramics.

Impact: Microwave resonators and superconducting filters commonly adopt the perovskite structure (idealized in the figure to the right) and are extensively used in the multi-billion-dollar mobile telecommunications industry. Improving their properties could improve size reduction, speed, and quality.

Explanation: Novel perovskite ceramics of composition ABO3 have two atomic positions, A site and a B site, which can be readily modified. Varying the chemistry of these sites, relationships between composition, structure, and properties can be derived. Towards that end, powders of precisely controlled chemistries are being synthesized using an organic/inorganic method which uses a polymer to entangle the starting materials. The subsequent compounds are then characterized by advanced techniques, and the correlated results will aid in the development of a unique predictive model for the structure of realistic defect-containing perovskites. Computer modeling may allow for an understanding of the underlying physics of these effects.

The oxide perovskite structure contains A-site and B-site cations as well as oxygen. Each B-site is surrounded by six oxygen ions in octahedral coordination. Determining the exact cation and anion positions is complicated by the simultaneous possiblities of A- and B-cation displacements, cation ordering, and octahedral tilting.

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ion Processing and Analysis of Complex Oxides

Rick Ubic, Boise State University, DMR 1052788

Variation of the ideal perovskite structure can create useful properties like ferroelectricity, superconductivity, colossal magnetoresistance, and spin-dependent transport. Using the organic/inorganic steric entrapment method developed at UIUC, one can synthesize oxides such as La(ZnTi)½O3 from nitrate salts. A repeatable scientific method for synthesis of the oxides is crucial because of the compositional complexity:

[(Sr,Ca)zx(La,Nd)z-2zx/3][(Zn,Mg)2zy-y/2Ti3/2-3z/4-zy+y/4]O3

Effectively entrapping the cations requires further investigation, as producing single-phase La(ZnTi)½O3 has proven difficult, probably owing to the large molar weight differences of the cations. Producing single-phase materials is important for structural characterization and critical for dielectric property measurements. Utilizing parallel ab initio calculations may allow for the probing of the underlying physics, adding an additional dimension of understanding to the modeling of structure and phase transitions.

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Illustration of the steric entrapment method of La, Zn , and TiO2 particles entangled in polyvinyl alcohol

Test pellets are used to create SEM & TEM samples. The dielectric properties will be measured at Shanghai University.

X-ray diffraction pattern from near-single-phase La(ZnTi)0.5O3 grown using the inorganic/organic steric entrapment method

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ion Project Lead the Way

Rick Ubic, Boise State University, DMR 1052788

The four undergraduate students supported by this project at BSU will present their work to the public at the Discovery Center of Idaho and to hundreds of school-age children in the annual Jason Project, hosted by the College of Engineering. An exhibit called Wireless at BSU will expose these youngsters to electroceramics science and technology. A similar event occurs annually to provide the general public the same opportunity.

Kriven is involved in Project Lead the Way (PLTW), a national initiative to expose teachers and school children of diverse backgrounds to careers in engineering. Teachers come to an intensive short course to gain knowledge and teaching tools to use in their schools.

PLTW teacher training includes three phases, allowing teachers to study course-specific curriculum. PLTW classes are hands-on, based in real-world experience, and engaging for students and teachers setting the highest standards for rigorous, focused, and relevant study.

Drs. Ubic, Kriven, and Ceperley’s collaboration is an integral part to the processing of these complex oxides and development of theoretical models for predicting structure and properties.