There is provided a functional layer including a layered double hydroxide, which is composed of: a plurality of basic hydroxide layers including Ni, Al, Ti, and OH groups; and intermediate layers composed of anions and H.sub.2O, each intermediate layer being interposed between two adjacent basic hydroxide layers.

There is provided a functional layer including a layered double hydroxide. The layered double hydroxide does not undergo a change in the surface microstructure and the crystalline structure when immersed in 5 mol/L of an aqueous potassium hydroxide solution containing zinc oxide in a concentration of 0.4 mol/L at 70 C. for three weeks.

There is provided a functional layer including a layered double hydroxide. The layered double hydroxide does not undergo a change in the surface microstructure and the crystalline structure when immersed in 5 mol/L of an aqueous potassium hydroxide solution containing zinc oxide in a concentration of 0.4 mol/L at 70 C. for three weeks.

There is provided a functional layer including a layered double hydroxide that contains Ni, Al, Ti and Zn, and has an atomic ratio Zn/(Ni+Ti+Al+Zn) of 0.04 or more determined by an energy dispersive X-ray analysis (EDS).

There is provided a functional layer including a layered double hydroxide that contains Ni, Al, Ti and Zn, and has an atomic ratio Zn/(Ni+Ti+Al+Zn) of 0.04 or more determined by an energy dispersive X-ray analysis (EDS).

There is provided a functional layer including a layered double hydroxide (LDH). The functional layer includes a first layer with a thickness of 0.10 m or more, the first layer being composed of fine LDH particles having a diameter of less than 0.05 m, and a second layer composed of large LDH particles having a mean particle diameter of 0.05 m or more, the second layer being an outermost layer provided on the first layer.

There is provided a functional layer including a layered double hydroxide (LDH). The functional layer includes a first layer with a thickness of 0.10 m or more, the first layer being composed of fine LDH particles having a diameter of less than 0.05 m, and a second layer composed of large LDH particles having a mean particle diameter of 0.05 m or more, the second layer being an outermost layer provided on the first layer.

There is provided a functional layer including layered double hydroxide. The functional has an average porosity of 1 to 40% and an average pore diameter of 100 nm or less.

There is provided a functional layer including layered double hydroxide. The functional has an average porosity of 1 to 40% and an average pore diameter of 100 nm or less.

To provide a preparing method of a zirconia mill blank for dental cutting and machining having any one or more of translucency gradation, color gradation and strength gradation after perfect sintering by impregnating a zirconia calcined body with a plurality of impregnating solutions, which can suppress deterioration of the fitting property of a dental prosthesis device prepared from the zirconia mill blank for dental cutting and machining and a zirconia mill blank for dental cutting and machining having any one or more of translucency gradation, color gradation and strength gradation after perfect sintering and suppressing deterioration of the fitting property of a dental prosthesis device prepared from the zirconia mill blank for dental cutting and machining.

To porovide a zirconia mill blank for dental cutting and machining of the present invention is a preparing method of a zirconia mill blank for dental cutting and machining having any one or more of translucency gradation, color gradation and strength gradation after perfect sintering, comprising a step of impregnating a zirconia calcined body with at least two types of impregnating solutions, wherein at least one of the impregnating liquids contains a zirconium component, and in a case in which the total of metal ion concentrations (mass %) contained in each impregnating liquid is defined as C.sub.total, the difference ?C.sub.total which is a difference between C.sub.total of each impregnating liquid is 5.0 or less.