Abstract: A process for producing a complex oxide containing the valuable metal and an alkali (earth) metal salt, which comprising co-milling a mixture of the valuable metal oxide and/or a precursor thereof, or a mixture of a substance containing the valuable metal oxide and/or a precursor thereof, with an alkali (earth) metal salt to a particle size of the valuable metal oxide or a substance containing the oxide, of 10 ?m or less, and heating the co-milled product to a temperature of at least 200° C. so as to induce a solid-phase reaction of the valuable metal oxide with an alkali (earth) metal salt.

Abstract: A piezoelectric single crystal device is provided exhibiting excellent piezoelectric properties, within a specific high-temperature range of Trrt° C. to (Trt?20)° C., where Trt represents a transformation temperature between a pseudocubic system and a tetragonal system. Specifically, the piezoelectric single crystal device is composed of a single crystal having a composition represented by [Pb(Mg,Nb)O3](1-X)·[PbTiO3](X), where X is within the range of 0.26 to 0.29 and having a complex perovskite structure, wherein a specific inductive capacity at 25° C. is 5,000 or more, and a specific inductive capacity at the transformation temperature between a pseudocubic system and a tetragonal system of the above-described single crystal is 2.5 times or more larger than the specific inductive capacity at 25° C.

Abstract: A process for producing a complex oxide containing the valuable metal and an alkali (earth) metal salt, which comprising co-milling a mixture of the valuable metal oxide and/or a precursor thereof, or a mixture of a substance containing the valuable metal oxide and/or a precursor thereof, with an alkali (earth) metal salt to a particle size of the valuable metal oxide or a substance containing the oxide, of 10 ?m or less, and heating the co-milled product to a temperature of at least 200° C. so as to induce a solid-phase reaction of the valuable metal oxide with an alkali (earth) metal salt. The process improves the solid-phase reaction rate and the selectivity of the value metal complex oxide, which results in the enhancement of the productivity for the complex oxide.