A relaxor-PT based piezoelectric crystal is disclosed, comprising the general formula of (Pb.sub.1-1.5xM.sub.x){[(M.sub.I,M.sub.II).sub.1-z(M.sub.I′,M.sub.II′).sub.z].sub.1-yTi.sub.y}O.sub.3, wherein: M is a rare earth cation; M.sub.I is selected from the group consisting of Mg.sup.2+, Zn.sup.2+, Yb.sup.3+, Sc.sup.3+, and In.sup.3+; M.sub.II is Nb.sup.5+; M.sub.I′ is selected from the group consisting of Mg.sup.2+, Zn.sup.2+, Yb.sup.3+, Sc.sup.3+, In.sup.3+, and Zr.sup.4; M.sub.II′ is Nb.sup.5+ or Zr.sup.4+; 0<x≤0.05; 0.02<y<0.7; and 0≤z≤1, provided that if either M.sub.I′ or M.sub.II′ is Zr.sup.4+, both M.sub.I′ and M.sub.II′ are Zr.sup.4+. A method for forming the relaxor-PT based piezoelectric crystal is disclosed, comprising pre-synthesizing precursor materials by calcining mixed oxides, mixing the precursor materials with single oxides and calcining to form a feeding material, and growing the relaxor-PT based piezoelectric crystal having the general formula of (Pb.sub.1-1.5xM.sub.x){[(M.sub.I,M.sub.II).sub.1-z(M.sub.I′,M.sub.II′).sub.z].sub.1-yTi.sub.y}O.sub.3 from the feeding material by a Bridgman method.

The present invention makes clear and defines a congruent composition of a langasite-based oxide, and establishes a method of manufacturing a crystal by any desired composition of AE.sub.3ME.sub.1+a(Ga.sub.1−xAl.sub.x).sub.3+bSi.sub.2+cO.sub.14 (AE is an alkaline-earth metal, ME is Nb or Ta, 0≤x≤1, −0.5<a≤0 or 0<a<0.5, −0.5<b≤0 or 0<b≤0.5, and −0.5<c≤0 or 0<c<0.5, excluding a=b=c=0). This makes it possible to suppress the formation of an impurity, and improve the yield and crystal manufacturing rate. The raw material is a raw material mixture prepared by mixing an alkaline-earth metal or its carbonate or oxide, Nb or Ta or its oxide, Ga or its oxide, Al or its oxide, and Si or its oxide.

To provide a lithium niobate (LN) substrate which allows treatment conditions regarding a temperature, a time, and the like to be easily managed and in which an in-plane distribution of a volume resistance value is very small, and a method of producing the same. A method of producing an LN substrate by using an LN single crystal grown by the Czochralski process, in which an LN single crystal having a Fe concentration of more than 1000 mass ppm and 2000 mass ppm or less in the single crystal and processed into a form of a substrate is buried in an Al powder or a mixed powder of Al and Al.sub.2O.sub.3, and heat-treated at a temperature of 550 C. or more and 600 C. or less, to produce a lithium niobate single crystal substrate having a volume resistivity controlled to be within a range of 110.sup.8 .Math.cm or more to 110.sup.10 .Math.cm or less.

A piezoelectric material for a combustion pressure sensor, a method for producing the piezoelectric material, and a combustion pressure sensor using the piezoelectric material are provided. The piezoelectric material of the present invention includes a single crystal containing Ca, Ta, an element M (M is Al or Ga), Si, and O, the single crystal has the same crystal structure as the crystal structure of langasite represented by La.sub.3Ga.sub.5SiO.sub.14, and at least the content of the element M is insufficient for the stoichiometric composition represented by Ca.sub.3TaM.sub.3Si.sub.2O.sub.14. Preferably, in a case where the element M is Ga, each content of the Ca and the Si is excessive for the stoichiometric composition, and in a case where the element M is Al, the content of the Ca is excessive for the stoichiometric composition, and the content of the Ta is insufficient for the stoichiometric composition.

To provide a method of producing a lithium niobate (LN) substrate which allows treatment conditions regarding a temperature, a time, and the like to be easily managed and in which an in-plane distribution of a volume resistance value is very small, and also variations in volume resistivity are small among substrates machined from the same ingot. A method of producing an LN substrate by using an LN single crystal grown by the Czochralski process, in which a lithium niobate single crystal having a Fe concentration of 50 mass ppm or more and 2000 mass ppm or less in the single crystal and being in a form of an ingot is buried in an Al powder or a mixed powder of Al and Al.sub.2O.sub.3, and heat-treated at a temperature of 450 C. or more and less than 660 C., which is a melting point of aluminum, to produce a lithium niobate single crystal substrate having a volume resistivity controlled to be within a range of 110.sup.8 .Math.cm or more to 210.sup.12 .Math.cm or less.

A method for producing a piezoelectric film includes forming a metal film, recrystallizing a portion of the metal film by heating, forming an amorphous film of piezoelectric material on the metal film; and heating the amorphous film at a position of the recrystallized portion of the metal film.

The present invention makes clear and defines a congruent composition of a langasite-based oxide, and establishes a method of manufacturing a crystal by any desired composition of AE.sub.3ME.sub.1+a(Ga.sub.1-xAl.sub.x).sub.3+bSi.sub.2+cO.sub.14 (AE is an alkaline-earth metal, ME is Nb or Ta, 0x1, 0.5<a0 or 0<a<0.5, 0.5<b0 or 0<b0.5, and 0.5<c0 or 0<c<0.5, excluding a=b=c=0). This makes it possible to suppress the formation of an impurity, and improve the yield and crystal manufacturing rate. The raw material is a raw material mixture prepared by mixing an alkaline-earth metal or its carbonate or oxide, Nb or Ta or its oxide, Ga or its oxide, Al or its oxide, and Si or its oxide.

Methods and materials are disclosed for simultaneously optimizing both the piezoelectric and mechanical properties of wurtzite piezoelectric materials based on the AlN wurtzite and alloyed with one or two end-members from the set BN, YN, CrN, and ScN.

To provide a method of producing a lithium niobate (LN) substrate which allows treatment conditions regarding a temperature, a time, and the like to be easily managed and in which an in-plane distribution of a volume resistance value is very small, and also variations in volume resistivity are small among substrates machined from the same ingot.

A method of producing an LN substrate by using an LN single crystal grown by the Czochralski process, in which a lithium niobate single crystal having a Fe concentration of 50 mass ppm or more and 2000 mass ppm or less in the single crystal and being in a form of an ingot is buried in an Al powder or a mixed powder of Al and Al.sub.2O.sub.3, and heat-treated at a temperature of 450 C. or more and less than 660 C., which is a melting point of aluminum, to produce a lithium niobate single crystal substrate having a volume resistivity controlled to be within a range of 110.sup.8 .Math.cm or more to 210.sup.12 .Math.cm or less.

To provide a lithium niobate (LN) substrate which allows treatment conditions regarding a temperature, a time, and the like to be easily managed and in which an in-plane distribution of a volume resistance value is very small, and a method of producing the same.

A method of producing an LN substrate by using an LN single crystal grown by the Czochralski process, in which an LN single crystal having a Fe concentration of more than 1000 mass ppm and 2000 mass ppm or less in the single crystal and processed into a form of a substrate is buried in an Al powder or a mixed powder of Al and Al.sub.2O.sub.3, and heat-treated at a temperature of 550 C. or more and 600 C. or less, to produce a lithium niobate single crystal substrate having a volume resistivity controlled to be within a range of 110.sup.8 .Math.cm or more to 110.sup.10.Math.cm or less.