Materials Research Institute

Unique Ba(ZrxTi1-x)O3 Solid Solution SystemRuyan Guo and Amar Bhalla (co-PIs), Penn State University, DMR-0333191

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In our efforts to find new lead-free ferroelectric materials, we have investigated the system BaZrO3:BaTiO3. This solid solution system, depending on the composition, shows the properties of a simple dielectric (pure BaZrO3), quantum paraelectric, polar cluster dielectric, incipient ferroelectric, relaxor ferroelectric, ferroelectric with pinched transitions and then a proper ferroelectric (pure BaTiO3). So far there is no other single solid solution systems that demonstrates all aspects of ferroelectricity. This unique system, in single crystal, ceramic, and composite forms, is currently under study for understandings of its microstructure-property relationships and its applications as Pb-free ferroelectrics.

BZT crystal grown by LHPG

Fig. (top) Single crystal BZT crystals (x=0.05) grown by LHPG; (middle) dielectric properties of the BZT0.05 showing pinched phase transition; and (bottom) dielectric constant and loss as function of temperature and frequency for BZT0.25 showing typical ferroelectric relaxor behavior.

Materials Research Institute

A new method able to resolve high frequency EO properties is developed in Guo’s group couplingstanding or traveling microwaves with propagating light pulses (Fig. 1). The method isdemonstrated using an a-axis grown (by the laser heated pedestal growth method) SBN crystal at10 GHz. Using the slope of delta frequency and square root of power, the EO value at clamped boundary condition can be obtained (Fig. 2) to be r333

x=200.4pm/V, compared to that obtained at free mechanical boundary condition (r333

X=240~271 @~1KHz). The effective microwave photonic interactions demonstrated in relaxor ferroelectric SBN crystals is about one order of magnitude larger than that of LiNbO3 under the same conditions. The optical pulse in microwave cavity can be uptuned/downtuned, squeezed/expanded in the range of GHz, controlled by the relative position of optical pulse traversing the crystal fiber in the given microwave cavity. A range of photonic applications may be developed utilizing the microwave modulations, such as bandwidth definitions and wavelength tuning applications. One undergraduate student also participated the research in summer 2005.

Resolving Frequency Dependent Electrooptic Property of Relaxor Ferroelectric SBN Single Crystals

Ruyan Guo (PI), Penn State Univ., DMR-0333191 and DMR-0075917

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Fig. 1

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Huang, Guo, Bhalla, APL, 86 (2005) 131106 & Huang, Bhalla, Guo, APL 86 (2005) 211907