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Nonstoichiometric LiTaO3 ceramics doped with 15 mol % CaTiO3 have been prepared to improve the piezoelectricity of LiTaO3 ceramics and iron doping has been investigated to obtain a high mechanical quality factor, Qm. By increasing the ratio of B sites (Ta and Ti) from 49.5 to 52.0 mol %, crack generation was suppressed and resonance frequency in the radial vibration mode shifted. (Li0.84Ca0.15)(Ta0.86Ti0.15)O3 ceramics whose A and B site ratios were 49.5 and 50.5 mol %, respectively, caused a higher resonance frequency and a high piezoelectric activity than the stoichiometric LiTaO3. The optimum composition for the piezoelectric properties was obtained from the nonstoichiometric LiTaO3 expressed as (Li0.832Ca0.158)(Ta0.856Ti0.15Fe0.004)O3; the phase shift was 73° and the quality factor Qm was 7872 in the radial vibration mode. Although the phase shift is still not sufficiently high, it is expected to approach 90° by fixing it under better poling conditions. One of the possible applications of this material is as an oscillator element for signal processing circuits.

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Oxygen vacancy behaviors in Ni-doped barium strontium titanate (BST) ceramics have been observed through thermally stimulated current (TSC) measurements up to 200°C. The set of observations confirmed that the vacancies drift due to a high electric field at an elevated temperature to pile up under the cathode electrode and the initial complex defects of acceptor, NiTi ′′, and donor, VO ••, are separated from each other forming a forward-biased pn junction. It is also revealed that the oxygen vacancies are newly generated at the anode area either if the ceramic surface is roughened or if a catalytic electrode such as Pt is attached.

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