The paraelectric cubic structure of (Bi 1/2 Na 1/2 )TiO 3 was analyzed precisely by high-energy synchrotron radiation X-ray powder diffraction measurement and the maximum entropy method (MEM)/Rietveld method. The o100p-favored rotator-like thermal behavior of the Bi ion was observed. The o100p off-centering of Bi led to the Bi-O distance of >2.5 Å that was shorter than the average Bi-O distance in the structure of the Bi on-centered model. The off-centering of Bi can be attributed to the orbital hybridization between the Bi and O ions.

Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ∼104 times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si−O−Si angles bridging rigid SiO4 tetrahedra, which efficiently transduce electric energy into elastic energy.

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The momentary crystal structure of a Y-cut langasite oscillator resonantly vibrating under an alternating electric field is revealed by time-resolved crystal structure analysis to understand the microscopic mechanism of piezoelectricity. The thickness-shear lattice strain under an electric field is amplified ∼103 times by the resonant effect. The lattice vibration involves the deformation of GaO4 and Ga0.5Si0.5O4 tetrahedra accompanied by atomic displacements of specific oxygen atoms along the electric field. The deformation of GaO4 and Ga0.5Si0.5O4 tetrahedra enhances the piezoelectricity of langasite.