Papers by Author: Youichi Mizuno

Abstract: The Relationship between the Piezoelectric Properties and Crystal Lattice Deformation and Distortion Resulting from the Li Substitution in Li_XNa_0.52K_0.48-XNbO₃, Alkaline Niobate-Based Perovskite Ceramics of (Li, Na, K)NbO₃, Was Investigated. the Lattice Parameters of the Sample with a Li Content X = 0.05 and Having a Monoclinic System with Space Group PM Were a = 3.9789(6) Å, B = 3.9385(5) Å, C = 4.0134(6) Å, and B = 90.305(4)º. the E^T33/e0, Kr, and -D31 Values of the Sample by Poling in the Monoclinic System Were 450, 44.6%, and 57 PC/N, Respectively. on the other Hand, the E^T33/e0, Kr, and -D31 Values of the Sample by Poling in the Tetragonal System Were 600, 38.7%, and 56 PC/N, Respectively. the Remarkable Piezoelectric Properties of these Ceramics Can Be Attributed only to the Low Symmetry of their Monoclinic System, which Is a Subgroup of aMm2 and P4mm. Li_0.05Na_0.52K_0.43NbO₃ Ceramics with a Monoclinic System Were Observed to Have the Unique Piezoelectric Characteristics.

Abstract: The behavior of hydrogen in (Ba,Sr)TiO3 (BST) thin film capacitors under electric fields was investigated by performing secondary ion mass spectroscopy (SIMS) analyses. It was clearly observed that the ingress of atmospheric hydrogen into BST thin film capacitors occurred through the anode and that it diffused toward the cathode under electric fields. In addition, it was found that the deterioration of the I-V properties of the BST thin film capacitors can be interpreted in terms of the distribution of hydrogen concentration in the BST thin films.

Abstract: The nanoscale local structure of core-shell structured BaTiO3 grains with a nonuniform dopant distribution was studied by convergent beam electron diffraction. The direct measurements of the variation of lattice parameter in an individual BaTiO3 grain were achieved. It was found that the lattice parameter continuously increased from inside the grain core to the grain shell and there was no discontinuity at the core/shell interface. The increasing gradient of c-axes was slightly smaller than that of a-axes, suggesting that the perovskite unit cell in the grain shell has lower tetragonality.

Abstract: The relationship between the distribution of hydrogen and the electrical properties of (Ba, Sr)TiO3 (BST) thin film capacitors was investigated using secondary ion mass spectroscopy (SIMS) analyses. It has been clearly shown that there is a close relationship between the hydrogen distribution in BST thin film and the frequency dependence of the complex impedance of the BST thin film capacitors. It was confirmed that protons, the interstitial hydrogen impurity dissolved in BST thin films annealed at 400oC, were produced by a thermal equilibrium reaction between the hydrogen in the annealing atmosphere and the BST thin films.