JP3598243B2 - Piezoelectric single crystal composition and piezoelectric single crystal wafer thereof - Google Patents

Description

特にＢｉ圧電単結晶においては｛（Ｂｉ_１／２，Ｎａ_１／２）_１−ｘＢａ_ｘ｝ＴｉＯ_３で表される材料系に関して１〜１０ｍｍ程度の比較的小さな結晶が得られており、その圧電定数はｄ３３＝３００〜６５０ｐＣ／Ｎと現行のＰＺＴセラミックスに迫る勢いである。これらの情報はＹｅｔ−Ｍｉｎｇ Ｃｈｉａｎｇ，ＡＰＰｌＩＥＤ ＰＨＹＳＩＣＳ ＬＥＴＴＥＲＳ ＶＯＬＵＭＥ７３，ＮＵＭＢＥＲ２５，Ｐ．Ｐ．３６８３（１９９８）に示されている。室温での誘電率がεｒ≧７００、キュリー点がＴｃ≧２００℃、さらに圧電定数はｄ３３＝３００〜６５０ｐＣ／Ｎの非鉛系材料が容易に得られるようになれば幾つかの分野で鉛系圧電材料を置きかえることが可能であると考えられる。発明者はこれらの結晶を試作し、１５〜４０ｍｍφ×１０〜５０ｍｍ程度の比較的大きな結晶が得られるようになったが得られた結晶内には内包物、気泡およびクラックが多数存在し、振動子を得る上で非常に大きな問題となっている。
【０００５】
【発明が解決しようとする課題】
｛（Ｂｉ_１／２，Ｎａ_１／２）_１−ｘＡ１_ｘ｝ＴｉＯ_３等で表される固溶系単結晶は、その内部に内包物や気泡、あるいはクラックが存在しやすく、各種応用に用いる振動子として作製する際には、これらの欠陥領域を避けなければならない。例えば超音波診断装置用の心臓プローブ用振動子に要求される標準的なサイズは、１５ｍｍ×２５ｍｍ×０．４ｍｍであるものの、結晶内部の異物等の領域を避けて切り出すために、この形状の振動子の作製歩留まりが極めて悪いのが現状であった。
【０００６】
そこで、本発明の目的は、上記の問題点を解決すべく、｛（Ｂｉ_１／２，Ｎａ_１／２）_１−ｘＡ１_ｘ｝ＴｉＯ_３等 で表わされる単結晶を作製した時に、特性の低下を招くことなく単結晶の内部に内包物、気泡およびクラックが取り込まれにくい新規の酸化物単結晶組成物及びそのウェハーを提供するものである。
【０００７】
【課題を解決するための手段】
本発明者らは、鋭意研究した結果、｛（Ｂｉ_１／２，Ｎａ_１／２）_１−ｘＡ１_ｘ｝ＴｉＯ_３等 で表わされる単結晶組成が少なくとも１種類の５価の元素Ｄ（Ｄ＝Ｎｂ，Ｔａ）を含有することで前記課題であった単結晶内部の内包物や気泡およびクラック等の発生を誘電・圧電特性の劣化を招くことなく飛躍的に減少できることを見出した。
【０００８】
本発明は｛（Ｂｉ_１／２，Ｎａ_１／２）_１−ｘＡ１_ｘ｝ＴｉＯ_３（式中、ｘは０≦ｘ＜１の値であり、Ａ１はＢａ，Ｃａ，およびＳｒから選択された少なくとも１種類である）および｛（Ｂｉ_１／２，Ｎａ_１／２）_１−ｘ（Ｂｉ_１／２，Ａ２_１／２）_ｘ｝ＴｉＯ_３（式中のｘは０≦ｘ＜１の値であり、Ａ２はＬｉ，Ｋ，およびＲｂから選択された少なくとも１種類である）で表される複合ペロブスカイト酸化物から構成される圧電単結晶組成物において、組成物１００ｍｏｌ％に対して５価の元素Ｄ（Ｄ＝Ｎｂ ^５＋ ，Ｔａ ^５＋ ）を含む化合物を０＜Ｄ＜５ｍｏｌ％すなわちＤ元素換算で０ｍｏｌ％を越え５ｍｏｌ％未満の範囲で添加することを特徴とする酸化物単結晶組成物を提供することである。なお、Ｎｂ^５＋やＴａ^５＋を含む際に（Ｚｎ_１／３Ｎｂ_２／３）Ｏ_２や（Ｓｃ_１／２Ｎｂ_１／２）Ｏ_２、（Ｍｇ_１／３Ｔａ_２／３）Ｏ_２の複合構造の形態で含むことも可能であり、これらも本発明の範囲内である。また本発明の複合ペロブスカイト酸化物から構成される圧電単結晶において、その結晶の方位が菱面体構造の場合には｛００１｝方向で分極し、正方晶相の場合には｛１１１｝方向に分極することでその優れた特性をより有効に出すことが出来る。以下の実施形態をＮｂ ^５＋ で説明するが、Ｔａ ^５＋ も同族でかつＮｂ ^５＋ と同じイオン半径を持ち、Ｔｉのそれに近いので、同様の効果を得ることができる。
【０００９】
【発明の実施の形態】
以下、本発明の実施の形態を実施例を基に説明する。
（実施例１）
本実施例においては、｛（Ｎａ_１／２，Ｂｉ_１／２ ）_０．９４Ｂａ_０．０６｝ＴｉＯ_３＋ｙＮｂ_２Ｏ_５（以下ＮＢＢＴ９４／６ ＋ｙｍｏｌ％Ｎｂ _２ Ｏ _５ と略す）で表されるＮｂ_２Ｏ_５を添加した固溶系圧電単結晶をブリッジマン法にて作製した（ここで、ｙ＝０．１、０．５、１．０、２．０ｍｏｌ％とした）。今回用いたブリッジマン法について単結晶の育成装置の図面を参照して説明する。図１は、単結晶の育成装置を示す概略図である。図中の１は、上下方向にヒータ２が埋設された縦型管状電気炉である。図中の３は、前記電気炉１内に上下動自在に配置される有底筒状容器である。まず、前記有底筒状容器３内に単結晶原料を収容する。次にこの有底筒状容器３をヒータ２により中央部が最も高温度で、上方および下方に向かうにしたがって温度が低くなるように設定した、つまり温度勾配を持たせた電気炉１内に下から支える。つづいて、前記電気炉１内で有底筒状容器３内の単結晶原料を溶融した後、前記容器３を徐々に下降させることにより溶液あるいは融液４が収容された前記容器３の底部が局所的に低温になり、前記底部位置に単結晶の核が発生し、この単結晶の核から単結晶が成長するといった方法である。
【００１０】
出発原料として、化学的に高純度なＮａ_２ＣＯ_３、Ｂｉ_２Ｏ_３、ＢａＣＯ_３、ＴｉＯ_２およびＮｂ_２Ｏ_５の粉末を使用し、これらを上述の式で示した組成となるように調合し、乾式混合機械で十分に混合した。得られた混合粉をアルミナ坩堝に充填し、大気中にて８５０℃、２時間の仮焼を行った。その後この仮焼粉にアセトンを加え、ジルコニアボールを用いてボールミルで２４時間混合・粉砕した。この粉体を乾燥しバインダーとしてのＰＶＡ５％水溶液を５ｗｔ％加えて乳鉢で混合し、４８＃の篩を通過させて造粒を行なった。得られた粒子を、１５ｍｍφの金型内で５ＭＰａの圧力を加えて１０ｍｍの円柱状に仮成型した。この成型体を大気中にて１０００℃〜１２００℃２時間の焼成を行って焼結体を得た。この焼結体を前述した図１内の１５ｍｍφ×２００ｍｍの有底筒状白金容器３内に入れた。つづいて、中央部の温度が１２５０℃〜１３５０℃、上下方向に２分割されたヒータ２により上下方向の平均温度勾配が０．５℃／ｍｍから３℃／ｍｍとした内径５０ｍｍ、長さ１０００ｍｍの縦型電気炉１に前記白金容器３を下支えにし、１３５０℃の温度まで７時間で昇温した後、１２時間保持して前記容器３内の結晶原料を溶融させた。ついで、前記白金容器３を電気炉１の中央により下部の温度勾配部分に向かって０．５ｍｍ／ｈ〜２ｍｍ／ｈの速度で約５００ｍｍ下降させ、その後室温まで放冷した。前記白金容器をそれぞれ破り、４組成の単結晶を取り出した。得られた４つ単結晶はどれも１５ｍｍφ×４０ｍｍのやや淡黄色をした透明結晶であった。懸念された内包物、気泡およびクラックは前記形状内に気泡およびクラックが一部で確認できる組成もみられたがその数は明らかに減少していることが外観上から確認された。前記単結晶の結晶構造をＸ線回折法より調べたところ、室温で菱面体のぺロブスカイト構造であることが分かった。また、前記単結晶の粉末のＩＣＰによる化学分析から得られた結晶組成はそれぞれがほぼ仕込み組成｛（Ｎａ_１／２，Ｂｉ_１／２ ）_０．９４Ｂａ_０．０６｝ＴｉＯ_３＋ｙＮｂ_２Ｏ_５（ｙ＝０．１、０．５、１．０、２．０ｍｏｌ％）となっていることを確認した。
【００１１】
ついで前記単結晶のそれぞれについてＸ線ラウエカメラを用いて＜１００＞方位軸を出し、この軸に垂直にカッターで厚さが１ｍｍの{１００}面単結晶版を切り出した。その後特性評価のために前記単結晶版を１０ｍｍ×１０ｍｍ×０．４ｍｍに仕上げたものを３０枚ずつ用意した。これらの板状単結晶の内部を観察し内包物、気泡およびクラックの数を観測した。ＮＢＢＴ９４／６ ＋０．１ｍｏｌ％Ｎｂ_２Ｏ_５では気泡あるいはクラックの入った単結晶板が１枚、ＮＢＢＴ９４／６ ＋０．５ｍｏｌ％Ｎｂ_２Ｏ_５では内包物、気泡およびクラックは皆無、ＮＢＢＴ９４／６ ＋１．０ｍｏｌ％Ｎｂ_２Ｏ_５およびＮＢＢＴ９４／６ ＋２．０ｍｏｌ％Ｎｂ _２ Ｏ _５ ではクラックのみ含んだ単結晶板が２枚ずつ存在した。これらの結果を比較例の結果と比較検討したものが図３である。図３からも明らかな通りＮｂを含まないＮＢＢＴ９４／６ の組成においては３０枚の単結晶板内に内包物、気泡およびクラックの少なくとも１つ以上を含むものが９枚存在したのに対しＮｂを含む組成においては最大２枚、また組成によっては皆無のものも存在した。
【００１２】
また、前記単結晶板にＴｉ／Ａｕ電極をスパッタ法にて形成し電気的測定を行ったところ室温での誘電率はεｒ＝７００〜１８００、キュリー点はＴｃ＝２５０℃〜３２０℃、また圧電特性としてはｄ３３＝３００〜６５０ｐＣ／Ｎが得られた。
（実施例２）
本実施例においては、前記単結晶育成法にて４０ｍｍφの有底筒状白金容器３を用いて｛（Ｎａ_１／２，Ｂｉ_１／２ ）_０．９４Ｂａ_０．０６｝ＴｉＯ_３ ＋ｙＮｂ_２Ｏ_５（以下ＮＢＢＴ９４／６ ＋ｙｍｏｌ％Ｎｂ _２ Ｏ _５ と略す）で表されるＮｂ_２Ｏ_５を添加した大型圧電単結晶を作製した（ここで、ｙ＝０．１、０．５、１．０、２．０ｍｏｌ％とした）。
【００１３】
出発原料として、化学的に高純度なＮａ_２ＣＯ_３、Ｂｉ_２Ｏ_３、ＢａＣＯ_３、ＴｉＯ_２およびＮｂ_２Ｏ_５の粉末を使用し、これらを上述の式で示した組成となるように調合し、乾式混合機械で十分に混合した。得られた混合粉をアルミナ坩堝に充填し、大気中にて８５０℃、２時間の仮焼を行った。その後この仮焼粉にアセトンを加え、ジルコニアボールを用いてボールミルで２４時間混合・粉砕した。この粉体を乾燥しバインダーとしてのＰＶＡ５％水溶液を５ｗｔ％加えて乳鉢で混合し、４８＃の篩を通過させて造粒を行なった。得られた粒子を、３７ｍｍφの金型内で５ＭＰａの圧力を加えて１５ｍｍの円柱状に仮成型した。この成型体を大気中にて１０００℃〜１２００℃２時間の焼成を行って焼結体を得た。この焼結体を前述した図１内の４０ｍｍφ×２００ｍｍの有底筒状白金容器３内に入れた。つづいて、中央部の温度が１２５０℃〜１３５０℃、上下方向に２分割されたヒータ２により上下方向の平均温度勾配が０．５℃／ｍｍから３℃／ｍｍとした内径５０ｍｍ、長さ１０００ｍｍの縦型電気炉１に前記白金容器３を下支えにし、１３５０℃の温度まで７時間で昇温した後、１２時間保持して前記容器３内の結晶原料を溶融させた。ついで、前記白金容器３を電気炉１の中央により下部の温度勾配部分に向かって０．５ｍｍ／ｈ〜２ｍｍ／ｈの速度で約５００ｍｍ下降させ、その後室温まで放冷した。前記白金容器をそれぞれ破り、４組成の単結晶を取り出した。得られた４つ単結晶はどれも４０ｍｍφ×４０ｍｍのやや淡黄色をした透明結晶であった。また、懸念された内包物、気泡およびクラックは前記形状内に気泡およびクラックが一部で確認できる組成もみられたがその数は実施例１と同様に明らかに減少していることが外観上から確認された。前記単結晶の結晶構造をＸ線回折法より調べたところ、室温で菱面体のぺロブスカイト構造であることが分かった。また、前記単結晶の粉末のＩＣＰによる化学分析から得られた結晶組成はそれぞれがほぼ仕込み組成｛（Ｎａ_１／２，Ｂｉ_１／２）_０．９４Ｂａ_０．０６｝ＴｉＯ_３＋ｙＮｂ_２Ｏ_５（ｙ＝０．１、０．５、１．０、２．０ｍｏｌ％）となっていることを確認した。
【００１４】
ついで前記単結晶のそれぞれについてｘ線ラウエカメラを用いて＜１００＞方位軸を出し、この軸に垂直にカッターで厚さが１ｍｍの｛１００｝面単結晶版を切り出した。その後特性評価のために前記単結晶版を２０ｍｍ×２０ｍｍ×０．４ｍｍに仕上げたものを３０枚ずつ用意した。これらの板状単結晶の内部を観察し内包物、気泡およびクラックの数を観測した。ＮＢＢＴ９４／６＋０．１ｍｏｌ％Ｎｂ_２Ｏ_５では気泡あるいはクラックの入った単結晶板が２枚、ＮＢＢＴ９４／６＋０．５ｍｏｌ％Ｎｂ_２Ｏ_５ではクラックの入った単結晶板が１枚、ＮＢＢＴ９４／６＋１．０ｍｏｌ％Ｎｂ_２Ｏ_５およびＮＢＢＴ９４／６＋２．０ｍｏｌ％Ｎｂ_２Ｏ_５ではクラックのみ含んだ単結晶板が３枚ずつ存在した。これらの結果を比較例の結果と比較検討したものが図３である。図３からも明らかな通りＮｂを含まないＮＢＢＴ９４／６の組成においては３０枚の単結晶板内に内包物、気泡およびクラックの少なくとも１つ以上を含むものが１４枚存在したのに対しＮｂを０．１ｍｏｌ％含む組成において２枚、０．５ｍｏｌ％含む組成において１枚、１．０および２．０ｍｏｌ％含む組成において３枚とその枚数は減少していることが分かる。
【００１５】
また、前記単結晶板にＴｉ／Ａｕ電極をスパッタ法にて形成し電気的測定を行ったところ室温での誘電率はεｒ＝７００〜１８００、キュリー点はＴｃ＝２５０℃〜３２０℃、また圧電特性としてはｄ３３＝３００〜６５０ｐＣ／Ｎと実施例１とほぼ同等の値が得られた。
（実施例３）
本実施例においては、前記単結晶育成法にて４０ｍｍφの有底筒状白金容器３を用いて０．９５｛（Ｎａ_１／２，Ｂｉ_１／２ ）_０．９４Ｂａ_０．０６｝ＴｉＯ_３ ＋０．０５｛（Ｎａ_１／２，Ｂｉ_１／２ ）_０．９４Ｂａ_０．０６｝（Ｚｎ _１／３ Ｎｂ _２／３ ）Ｏ_３で表される大型圧電単結晶を作製した。
【００１６】
出発原料として、化学的に高純度なＮａ_２ＣＯ_３、Ｂｉ_２Ｏ_３、ＢａＣＯ_３、ＴｉＯ_２、Ｎｂ_２Ｏ_５およびＺｎＯの粉末を使用し、これらを上述の式で示した組成となるように調合し、乾式混合機械で十分に混合した。その他の方法は前述と同様である。。得られた単結晶は４０ｍｍφ×４０ｍｍのやや淡黄色をした透明結晶であった。また、懸念された内包物、気泡およびクラックは見られず実施例１と同様に明らかに減少していることが外観上から確認された。前記単結晶の結晶構造をＸ線回折法より調べたところ、室温で菱面体のぺロブスカイト構造であることが分かった。また、前記単結晶の粉末のＩＣＰによる化学分析から得られた結晶組成はそれぞれがほぼ仕込み組成となっていることを確認した。
【００１７】
また、前記単結晶板にＴｉ／Ａｕ電極をスパッタ法にて形成し電気的測定を行ったところ室温での誘電率はεｒ＝１５００、キュリー点はＴｃ＝３００℃、また圧電特性としてはｄ３３＝６００ｐＣ／Ｎと実施例１とほぼ同等の値が得られた。
【００１８】
（比較例１）
本比較例においては、前記単結晶育成法にて１５ｍｍφおよび４０ｍｍφの有底筒状白金容器３を用いて｛（Ｎａ_１／２，Ｂｉ_１／２ ）_０．９４Ｂａ_０．０６｝ＴｉＯ_３で表されるＮｂ_２Ｏ_５を添加していない固溶系圧電単結晶を作製し、その特性を比較した。
【００１９】
出発原料として、化学的に高純度なＮａ_２ＣＯ_３、Ｂｉ_２Ｏ_３、ＢａＣＯ_３、およびＴｉＯ_２の粉末を使用し、これらを上述の式で示した組成となるように調合し、乾式混合機械で十分に混合した。得られた混合粉をアルミナ坩堝に充填し、大気中にて８５０℃、２時間の仮焼を行った。その後この仮焼粉にアセトンを加え、ジルコニアボールを用いてボールミルで２４時間混合・粉砕した。この粉体を乾燥しバインダーとしてのＰＶＡ５％水溶液を５ｗｔ％加えて乳鉢で混合し、４８＃の篩を通過させて造粒を行なった。得られた粒子を、１５ｍｍφあるいは３７ｍｍφの金型内で５ＭＰａの圧力を加えて１０ｍｍ〜１５ｍｍの円柱状に仮成型した。この成型体を大気中にて１０００℃〜１２００℃２時間の焼成を行って焼結体を得た。この焼結体を前述した図１内の１５ｍｍφ×２００ｍｍあるいは４０ｍｍφ×２００ｍｍの有底筒状白金容器３内に入れた。つづいて、中央部の温度が１２５０℃〜１３５０℃、上下方向に２分割されたヒータ２により上下方向の平均温度勾配が０．５℃／ｍｍから３℃／ｍｍとした内径５０ｍｍ、長さ１０００ｍｍの縦型電気炉１に前記白金容器３を下支えにし、１３５０℃の温度まで７時間で昇温した後、１２時間保持して前記容器３内の結晶原料を溶融させた。ついで、前記白金容器３を電気炉１の中央により下部の温度勾配部分に向かって０．５ｍｍ／ｈ〜２ｍｍ／ｈの速度で約５００ｍｍ下降させ、その後室温まで放冷した。前記白金容器をそれぞれ破り単結晶を取り出した。得られた２つの単結晶は１５ｍｍφ×４０ｍｍあるいは４０ｍｍφ×４０ｍｍのやや淡黄色をした透明結晶であった。また、内包物、気泡およびクラックは前記形状内に無数に存在することが外観上から確認された。前記単結晶の結晶構造をＸ線回折法より調べたところ、室温で菱面体のぺロブスカイト構造であることが分かった。また、前記単結晶の粉末のＩＣＰによる化学分析から得られた結晶組成はそれぞれがほぼ仕込み組成｛（Ｎａ_１／２，Ｂｉ_１／２ ）_０．９４Ｂａ_０．０６｝ＴｉＯ_３となっていることを確認した。
【００２０】
ついで前記単結晶のそれぞれについてｘ線ラウエカメラを用いて＜１００＞方位軸を出し、この軸に垂直にカッターで厚さが１ｍｍの｛１００｝面単結晶版を切り出した。その後特性評価のために前記単結晶版を１０ｍｍ×１０ｍｍ×０．４ｍｍあるいは２０ｍｍ×２０ｍｍ×０．４ｍｍに仕上げたものを３０枚ずつ用意した。これらの板状単結晶の内部を観察し内包物、気泡およびクラックの数を観測した。その結果１５ｍｍφの場合には気泡あるいはクラックの入った単結晶板が９枚、４０ｍｍφの場合には１４枚存在した。これらの結果を前記実施例と比較検討したものが図３である。図３からも明らかな通り、ＮＢＢＴ９４／６単結晶はＮｂ^５＋を僅かに含むことで育成時の内包物、気泡およびクラックの発生が抑制されることが明らかになった。
【００２１】
また、前記単結晶板にＴｉ／Ａｕ電極をスパッタ法にて形成し電気的測定を行ったところ室温での誘電率はεｒ＝７００〜１８００、キュリー点はＴｃ＝２５０℃〜３２０℃、また圧電特性としてはｄ３３＝３００〜６５０ｐＣ／Ｎと実施例１およびとほぼ同等の値が得られた。
【００２２】
なお、本発明では出発原料としてＢａＣＯ_３などの炭酸塩を用いたがこれ以外の例えばＢａＴｉＯ_３やＣａＴｉＯ_３などの形態の化合物を用いても良い。さらにこれらの特性を劣化させない範囲内で少量の遷移金属であるＭｎ、Ｃｏ、Ｆｅなどを含むこともこの発明の範囲内である。これらの遷移金属の量は多くても１ｍｏｌ％以下である。
【００２３】
【発明の効果】
以上詳述したように、本発明によれば、内包物や気泡およびクラックが少ない大型な単結晶が容易に得ることが可能で優れた誘電・圧電特性を持った非鉛系圧電単結晶材料が安価に安定に実用レベルで提供することが出来る。特に実用レベルの誘電率（≧１０００）とキュリー温度（Ｔｃ≧２００℃）および大型サイズ（≧２５ｍｍ）の非鉛系圧電材料を提供できる。本発明の圧電単結晶は、超音波プローブの振動子として特に有効であるが、これ以外にも、圧電ブザー等の電気音響変換器の用途にて効果を発揮することが期待される。なお、本発明の圧電単結晶は鉛を全く使用していない。そのため現在多くの圧電体応用の分野で使用されているＰＺＴやＰＭＮ等の鉛系圧電材料では避けることのできなかった、焼成、溶融等の熱処理プロセスでの酸化鉛の大気中への多量の揮発、拡散を完全に無くすことが可能となった。これは、今後必然的に生じるであろう鉛問題に対する根本的な解決策であり、生態学的な見地及び公害防止の面からも、極めて大きな効果を持つものである。
【図面の簡単な説明】
【図１】本発明に関わる酸化物圧電単結晶を製造するための育成装置を示す概略図。
【図２】本発明によって得られた圧電単結晶ウェハーの概略図。
【図３】本発明において得られた圧電単結晶の育成時の内包物、気泡あるいはクラックの発生とＮｂ_２Ｏ_５添加量の関係を示す図。
【符号の説明】
１．．．電気炉
２．．．ヒータ
３．．．白金坩堝
４．．．単結晶原料
５．．．単結晶
６．．．単結晶から｛１００｝あるいは｛１１１｝に切り出したウェハー[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel piezoelectric single crystal composition and a single crystal wafer used in the fields of an ultrasonic probe, a sonar, an ink jet printer head, a buzzer, an actuator, a sensor and a resonator.
[0002]
[Prior art]
Piezoelectric materials generate distortion (conversion of electrical energy to mechanical energy) when an electric field is applied from the outside, and generate electric charge on the surface when subjected to external stress (to convert electrical energy to mechanical energy). Is a material having a piezoelectric effect, and is widely used in fields such as an ultrasonic probe, an ink jet printer head, a buzzer, an actuator and a sensor, and a resonator.
[0003]
For example, in the field of ultrasonic imaging devices, in order to image the internal state of an object, an ultrasonic wave of a certain frequency is generated and transmitted into the object, and the ultrasonic wave reflected in the object is received. Enables imaging. A piezoelectric body is used as a vibrator that enables transmission / reception, that is, conversion from electrical energy to mechanical energy and conversion from mechanical energy to electrical energy. In addition, examples of an ultrasonic imaging apparatus employing such an ultrasonic probe include a medical diagnostic apparatus for inspecting the inside of a human body and an inspection apparatus for detecting a flaw inside metal welding.
[0004]
Most of piezoelectric materials currently put to practical use _is a PbZrO ₃ (PZ) -PbTiO 3 solid solution system consisting of (PT) (PZT system). The reason is that a material having excellent piezoelectric properties can be obtained by using a composition near the compositional phase boundary (MPB) of trigonal PZ and tetragonal PT. is there. PZT uses this M.P. P. B. A wide variety of composition lineups have been developed to meet a wide variety of needs by adding various subcomponents and additive components to the composition. They have a large mechanical constant (Qm) but a large piezoelectric constant (dij), and are suitable for applications such as positioning actuators. Various types have been developed, including those having a large (Qm) and suitable for applications such as ultrasonic generating elements such as ultrasonic motors. However, these lead-based piezoelectric materials contain a large amount of lead oxide (PbO), which is highly volatile even at low temperatures, as a main component. For example, in PZT and lead magnesium niobate PMN, about two thirds by weight is lead oxide. When these piezoelectric materials are manufactured as ceramics or single crystals, heat treatment such as sintering and melting is an inevitable process, and when considered at the industrial level, the volatility of lead oxide, a volatile component, to the atmosphere, The amount of diffusion is extremely large. Therefore, it can be said that the application of piezoelectric ceramics and single crystals will expand in the future and the amount of piezoelectric crystals and single crystals will increase. Therefore, from the viewpoint of ecological point of view and pollution prevention, there is a need for a lead-free or low-lead material that exhibits excellent piezoelectric properties. From these backgrounds, research on lead-free piezoelectric materials has gradually started, but in order to replace PZT ceramics currently used in many applications, it is necessary to have a large dielectric constant, a high Curie point, and further lead-free. Attention has been focused on Bi-based piezoelectric materials as materials satisfying such conditions (see Table 1).
[Table 1]

Particularly, in the case of a Bi piezoelectric single crystal, a relatively small crystal of about 1 to 10 mm is obtained for a material system represented by {(Bi _1/2 , Na _1/2 ) _1-x Ba _x } TiO _3. The piezoelectric constant is d33 = 300 to 650 pC / N, which is close to current PZT ceramics. These information are disclosed in Yet-Ming Chiang, APPLIED PHYSICS LETTERS VOLUME 73, NUMBER 25, P.S. P. 3683 (1998). If lead-free materials having a dielectric constant at room temperature of εr ≧ 700, a Curie point of Tc ≧ 200 ° C., and a piezoelectric constant of d33 = 300 to 650 pC / N can be easily obtained, lead-based materials will be used in some fields. It is considered possible to replace the piezoelectric material. The inventor prototyped these crystals and obtained relatively large crystals of about 15 to 40 mmφ × 10 to 50 mm. However, many crystals, inclusions, bubbles and cracks were present in the obtained crystals, It is a very big problem in getting a child.
[0005]
[Problems to be solved by the invention]
｛(Bi _1/2 , Na _1/2 ) _1-x A1 _x固 A solid solution single crystal represented by TiO ₃ or the like easily contains inclusions, bubbles, or cracks therein, and is used for various applications. When manufacturing as a vibrator, these defective regions must be avoided. For example, the standard size required for a transducer for a heart probe for an ultrasonic diagnostic apparatus is 15 mm × 25 mm × 0.4 mm. At present, the production yield of the vibrator is extremely poor.
[0006]
Therefore, an object of the present invention is to solve the above-mentioned problems by producing a single crystal represented by {(Bi _1/2 , Na _1/2 ) _1-x A1 _x ｝ TiO _3, etc. An object of the present invention is to provide a novel oxide single crystal composition in which inclusions, bubbles, and cracks are less likely to be taken into the single crystal without lowering, and a wafer thereof.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies and found that the single crystal composition represented by {(Bi _1/2 , Na _1/2 ) _1-x A1 _x ｝ TiO ₃ or the like has at least one pentavalent element D (D = Nb, Ta), the generation of inclusions, bubbles and cracks inside the single crystal, which was the above problem, can be drastically reduced without deteriorating the dielectric and piezoelectric characteristics.
[0008]
The present invention provides {(Bi _1/2 , Na _1/2 ) _1-x A1 _x } TiO ₃ (where x is a value of 0 ≦ x <1, and A1 is selected from Ba, Ca, and Sr. (Bi _1/2 , Na _1/2 ) _{1 -x} (Bi _1/2 , A2 _1/2 ) _x ｝ TiO ₃ (where x is 0 ≦ x <1) A2 is at least one selected from Li, K, and Rb) in a piezoelectric single crystal composition composed of a composite perovskite oxide represented by the following formula: An oxide single crystal composition characterized by adding a compound containing the element D (D = Nb ⁵⁺ , Ta ⁵⁺ ) in an amount of 0 <D <5 mol%, that is, more than 0 mol% and less than 5 mol% in terms of D element . It is to provide. When Nb ⁵⁺ or Ta ⁵⁺ is contained, (Zn _1/3 Nb _2/3 ) O ₂ , (Sc _1/2 Nb _1/2 ) O ₂ , (Mg _1/3 Ta _2/3 ) O ₂ It can also be included in the form of a composite structure, which is also within the scope of the present invention. In the piezoelectric single crystal composed of the composite perovskite oxide of the present invention, the crystal is polarized in the {001} direction when the crystal orientation is a rhombohedral structure, and is polarized in the {111} direction when the crystal is in a tetragonal phase. By doing so, the excellent characteristics can be more effectively obtained. The following embodiment will be described using Nb ⁵⁺ , but Ta ⁵⁺ is also homologous, has the same ionic radius as Nb ^5+, and is close to that of Ti, so that a similar effect can be obtained.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
(Example 1)
In this embodiment, {(Na _1/2 , Bi _1/2 ) _0.94 Ba _0.06 } TiO ₃ + yNb ₂ O ₅ (hereinafter abbreviated as NBBT94 / 6 + ymol% Nb ₂ O ₅ ) A solid solution piezoelectric single crystal to which Nb ₂ O ₅ was added was produced by the Bridgman method (here, y = 0.1, 0.5, 1.0, 2.0 mol%). The Bridgman method used this time will be described with reference to the drawing of a single crystal growing apparatus. FIG. 1 is a schematic view showing a single crystal growing apparatus. Reference numeral 1 in the figure denotes a vertical tubular electric furnace in which a heater 2 is embedded in a vertical direction. Reference numeral 3 in the figure denotes a bottomed cylindrical container which is arranged in the electric furnace 1 so as to be vertically movable. First, a single crystal raw material is accommodated in the bottomed cylindrical container 3. Next, the bottomed cylindrical container 3 was set by the heater 2 so that the temperature was the highest in the central part and the temperature became lower upward and downward, that is, the lower part was placed in the electric furnace 1 having a temperature gradient. Support from. Subsequently, after the single crystal raw material in the bottomed cylindrical container 3 is melted in the electric furnace 1, the container 3 is gradually lowered to lower the bottom of the container 3 containing the solution or the melt 4. The temperature is locally lowered, a single crystal nucleus is generated at the bottom position, and a single crystal grows from the single crystal nucleus.
[0010]
As a starting material, powders of chemically pure Na ₂ CO ₃ , Bi ₂ O ₃ , BaCO ₃ , TiO ₂ and Nb ₂ O ₅ are used, and these are prepared so as to have a composition represented by the above formula. And thoroughly mixed with a dry mixing machine. The obtained mixed powder was filled in an alumina crucible and calcined at 850 ° C. for 2 hours in the atmosphere. Thereafter, acetone was added to the calcined powder, and the mixture was mixed and pulverized with a ball mill using zirconia balls for 24 hours. The powder was dried, 5% by weight of a 5% aqueous solution of PVA as a binder was added, mixed in a mortar, and granulated by passing through a 48 # sieve. The obtained particles were provisionally molded into a 10 mm cylindrical shape by applying a pressure of 5 MPa in a 15 mmφ mold. This molded body was fired in the atmosphere at 1000 ° C. to 1200 ° C. for 2 hours to obtain a sintered body. This sintered body was placed in the above-mentioned cylindrical bottomed platinum container 3 of 15 mmφ × 200 mm in FIG. Subsequently, the inner temperature is 1250 ° C. to 1350 ° C., the inner temperature is 50 mm, the length is 1000 mm, and the average temperature gradient in the vertical direction is 0.5 ° C./mm to 3 ° C./mm by the heater 2 divided into two vertically. The platinum container 3 was supported by the vertical electric furnace 1 and the temperature was raised to 1350 ° C. in 7 hours, and then maintained for 12 hours to melt the crystal raw material in the container 3. Next, the platinum container 3 was lowered by about 500 mm at a speed of 0.5 mm / h to 2 mm / h toward the lower temperature gradient portion by the center of the electric furnace 1 and then allowed to cool to room temperature. The platinum containers were broken, and single crystals of four compositions were taken out. Each of the four single crystals obtained was a slightly pale yellow transparent crystal of 15 mmφ × 40 mm. Concerned inclusions, bubbles and cracks were found to have a composition in which bubbles and cracks could be partially observed in the shape, but the number was clearly reduced from the appearance. When the crystal structure of the single crystal was examined by an X-ray diffraction method, it was found that the single crystal had a rhombohedral perovskite structure at room temperature. In addition, the crystal compositions obtained by the chemical analysis of the single crystal powder by ICP are almost the same as the charged composition {(Na _1/2 , Bi _1/2 ) _0.94 Ba _0.06 {TiO ₃ + yNb ₂ O ₅ (Y = 0.1, 0.5, 1.0, 2.0 mol%).
[0011]
Then, an <100> azimuthal axis was set for each of the single crystals using an X-ray Laue camera, and a {100} plane single crystal plate having a thickness of 1 mm was cut out with a cutter perpendicular to this axis. After that, 30 sheets of the single crystal plate finished to 10 mm × 10 mm × 0.4 mm were prepared for characteristic evaluation. The inside of these plate-like single crystals was observed, and the number of inclusions, bubbles and cracks was observed. NBBT94 / 6 + 0.1 mol% Nb ₂ O ₅ has one single crystal plate containing bubbles or cracks, NBBT 94/6 + 0.5 mol% Nb ₂ O ₅ has no inclusions, bubbles and cracks, and NBBT 94/6 +1 single crystal plate which contains only cracks were present by two in .0mol% _Nb 2 _{O 5} and _{NBBT94 / 6 + 2.0mol% Nb 2} O 5. FIG. 3 shows a comparison of these results with the results of the comparative example. As is clear from FIG. 3, in the composition of NBBT94 / 6 containing no Nb, 30 sheets containing at least one of inclusions, bubbles and cracks were present in 30 single-crystal plates, whereas Nb was contained. There were a maximum of two compositions, and none of them depending on the composition.
[0012]
Further, a Ti / Au electrode was formed on the single crystal plate by a sputtering method, and an electrical measurement was performed. As a result, the dielectric constant at room temperature was εr = 700 to 1800, the Curie point was Tc = 250 ° C. to 320 ° C. As the characteristics, d33 = 300 to 650 pC / N was obtained.
(Example 2)
In this embodiment, {(Na _1/2 , Bi _1/2 ) _0.94 Ba _0.06 ｝ TiO ₃ + yNb ₂ O is used in the single crystal growing method by using a cylindrical platinum container 3 having a bottom of 40 mmφ. ₅ (hereinafter abbreviated as NBBT94 / 6 + ymol% Nb ₂ O ₅ ) to produce a large-sized piezoelectric single crystal to which Nb ₂ O ₅ was added (here, y = 0.1, 0.5, 1.0) , 2.0 mol%).
[0013]
As a starting material, powders of chemically pure Na ₂ CO ₃ , Bi ₂ O ₃ , BaCO ₃ , TiO ₂ and Nb ₂ O ₅ are used, and these are prepared so as to have a composition represented by the above formula. And thoroughly mixed with a dry mixing machine. The obtained mixed powder was filled in an alumina crucible and calcined at 850 ° C. for 2 hours in the atmosphere. Thereafter, acetone was added to the calcined powder, and the mixture was mixed and pulverized with a ball mill using zirconia balls for 24 hours. The powder was dried, 5% by weight of a 5% aqueous solution of PVA as a binder was added, mixed in a mortar, and granulated by passing through a 48 # sieve. The obtained particles were temporarily molded into a 15 mm cylindrical shape by applying a pressure of 5 MPa in a 37 mmφ mold. This molded body was fired in the atmosphere at 1000 ° C. to 1200 ° C. for 2 hours to obtain a sintered body. The sintered body was placed in the above-described 40 mmφ × 200 mm bottomed cylindrical platinum container 3 in FIG. Subsequently, the inner temperature is 1250 ° C. to 1350 ° C., the inner temperature is 50 mm, the length is 1000 mm, and the average temperature gradient in the vertical direction is 0.5 ° C./mm to 3 ° C./mm by the heater 2 divided into two vertically. The platinum container 3 was supported by the vertical electric furnace 1 and the temperature was raised to 1350 ° C. in 7 hours, and then maintained for 12 hours to melt the crystal raw material in the container 3. Next, the platinum container 3 was lowered by about 500 mm at a speed of 0.5 mm / h to 2 mm / h toward the lower temperature gradient portion by the center of the electric furnace 1 and then allowed to cool to room temperature. The platinum containers were broken, and single crystals of four compositions were taken out. Each of the obtained four single crystals was a slightly pale yellow transparent crystal of 40 mmφ × 40 mm. Concerned inclusions, bubbles and cracks were found to have a composition in which bubbles and cracks could be partially confirmed in the shape, but the number was clearly reduced as in Example 1 from the appearance. confirmed. When the crystal structure of the single crystal was examined by an X-ray diffraction method, it was found that the single crystal had a rhombohedral perovskite structure at room temperature. In addition, the crystal compositions obtained by the chemical analysis of the single crystal powder by ICP are almost the same as the charged composition {(Na _1/2 , Bi _1/2 ) _0.94 Ba _0.06 {TiO ₃ + yNb ₂ O ₅ (Y = 0.1, 0.5, 1.0, 2.0 mol%).
[0014]
Then, an <100> azimuthal axis was determined for each of the single crystals using an x-ray Laue camera, and a {100} plane single crystal plate having a thickness of 1 mm was cut out perpendicularly to this axis with a cutter. After that, for the purpose of evaluating the characteristics, 30 single crystal plates each having a size of 20 mm × 20 mm × 0.4 mm were prepared. The inside of these plate-like single crystals was observed, and the number of inclusions, bubbles and cracks was observed. _{NBBT94 / 6 + 0.1mol% Nb 2} O 5 single crystal plate containing the bubble or cracks in the two, one is _{NBBT94 / 6 + 0.5mol% Nb 2} O 5 single crystal plate containing the cracks in, NBBT94 / 6 + 1. 0 mol% _Nb 2 _{O 5} and _{NBBT94 / 6 + 2.0mol% Nb 2} O in ₅ containing only crack single crystal plate was present three pieces. FIG. 3 shows a comparison of these results with the results of the comparative example. As is apparent from FIG. 3, in the composition of NBBT94 / 6 containing no Nb, 30 single crystal plates contained 14 inclusions containing at least one of inclusions, bubbles and cracks, whereas Nb was contained. It can be seen that the number is reduced to two in the composition containing 0.1 mol%, one in the composition containing 0.5 mol%, and three in the composition containing 1.0 and 2.0 mol%.
[0015]
Further, a Ti / Au electrode was formed on the single crystal plate by a sputtering method, and an electrical measurement was performed. As a result, the dielectric constant at room temperature was εr = 700 to 1800, the Curie point was Tc = 250 ° C. to 320 ° C. As the characteristics, d33 = 300 to 650 pC / N, which is almost the same value as in Example 1.
(Example 3)
In the present example, 0.95 ｛(Na _1/2 , Bi _1/2 ) _0.94 Ba _0.06 ｝ TiO ₃ was used in the single crystal growing method by using a cylindrical platinum container 3 having a bottom of 40 mmφ. A large piezoelectric single crystal represented by +0.05 {(Na _1/2 , Bi _1/2 ) _0.94 Ba _0.06 } ( Zn _1/3 Nb _2/3 ) O ₃ was produced.
[0016]
As a starting material, powders of chemically high-purity Na ₂ CO ₃ , Bi ₂ O ₃ , BaCO ₃ , TiO _2, Nb ₂ O ₅ and ZnO are used so that they have the composition shown by the above formula. And thoroughly mixed with a dry mixing machine. Other methods are the same as described above. . The obtained single crystal was a slightly pale yellow transparent crystal of 40 mmφ × 40 mm. In addition, it was confirmed from the appearance that the inclusions, bubbles, and cracks that were concerned were clearly reduced as in Example 1. When the crystal structure of the single crystal was examined by an X-ray diffraction method, it was found that the single crystal had a rhombohedral perovskite structure at room temperature. In addition, it was confirmed that each of the single crystal powders obtained by chemical analysis by ICP had almost the same crystal composition as the charged composition.
[0017]
Further, a Ti / Au electrode was formed on the single crystal plate by a sputtering method, and an electrical measurement was performed. As a result, the dielectric constant at room temperature was εr = 1500, the Curie point was Tc = 300 ° C., and the piezoelectric characteristic was d33 = A value almost equal to 600 pC / N as in Example 1 was obtained.
[0018]
(Comparative Example 1)
In this comparative example, {(Na _1/2 , Bi _1/2 ) _0.94 Ba _0.06 } TiO ₃ was used in the single crystal growing method using the bottomed platinum platinum container 3 of 15 mmφ and 40 mmφ. A solid solution piezoelectric single crystal to which Nb ₂ O ₅ was not added was prepared, and its characteristics were compared.
[0019]
As a starting material, chemically high-purity powders of Na ₂ CO ₃ , Bi ₂ O ₃ , BaCO ₃ , and TiO ₂ are used, and these are blended so as to have a composition represented by the above formula, and dry-mixed. Mix well by machine. The obtained mixed powder was filled in an alumina crucible and calcined at 850 ° C. for 2 hours in the atmosphere. Thereafter, acetone was added to the calcined powder, and the mixture was mixed and pulverized with a ball mill using zirconia balls for 24 hours. The powder was dried, 5% by weight of a 5% aqueous solution of PVA as a binder was added, mixed in a mortar, and granulated by passing through a 48 # sieve. The obtained particles were provisionally molded into a cylindrical shape of 10 mm to 15 mm by applying a pressure of 5 MPa in a mold of 15 mmφ or 37 mmφ. This molded body was fired in the atmosphere at 1000 ° C. to 1200 ° C. for 2 hours to obtain a sintered body. The sintered body was placed in the above-mentioned cylindrical platinum container 3 having a bottom of 15 mmφ × 200 mm or 40 mmφ × 200 mm in FIG. Subsequently, the inner temperature is 1250 ° C. to 1350 ° C., the inner temperature is 50 mm, the length is 1000 mm, and the average temperature gradient in the vertical direction is 0.5 ° C./mm to 3 ° C./mm by the heater 2 divided into two vertically. The platinum container 3 was supported by the vertical electric furnace 1 and the temperature was raised to 1350 ° C. in 7 hours, and then maintained for 12 hours to melt the crystal raw material in the container 3. Next, the platinum container 3 was lowered by about 500 mm at a speed of 0.5 mm / h to 2 mm / h toward the lower temperature gradient portion by the center of the electric furnace 1 and then allowed to cool to room temperature. Each of the platinum containers was broken and a single crystal was taken out. The two obtained single crystals were 15 mmφ × 40 mm or 40 mmφ × 40 mm, slightly transparent yellowish transparent crystals. In addition, it was confirmed from the appearance that the inclusions, bubbles and cracks were numerous in the shape. When the crystal structure of the single crystal was examined by an X-ray diffraction method, it was found that the single crystal had a rhombohedral perovskite structure at room temperature. The crystal composition of the single crystal powder obtained by chemical analysis by ICP is almost the same as the charged composition {(Na _1/2 , Bi _1/2 ) _0.94 Ba _0.06 ｝ TiO ₃ . It was confirmed.
[0020]
Then, an <100> azimuthal axis was determined for each of the single crystals using an x-ray Laue camera, and a {100} plane single crystal plate having a thickness of 1 mm was cut out perpendicularly to this axis with a cutter. Thereafter, for the purpose of evaluating the characteristics, 30 single crystal plates each having a size of 10 mm × 10 mm × 0.4 mm or 20 mm × 20 mm × 0.4 mm were prepared. The inside of these plate-like single crystals was observed, and the number of inclusions, bubbles and cracks was observed. As a result, in the case of 15 mmφ, there were 9 single crystal plates containing bubbles or cracks, and in the case of 40 mmφ, there were 14 single crystal plates. FIG. 3 shows a comparison of these results with the above embodiment. As is clear from FIG. 3, it was revealed that the NBBT94 / 6 single crystal contained a small amount of Nb ⁵⁺ to suppress the generation of inclusions, bubbles and cracks during growth.
[0021]
Further, a Ti / Au electrode was formed on the single crystal plate by a sputtering method, and an electrical measurement was performed. As a result, the dielectric constant at room temperature was εr = 700 to 1800, the Curie point was Tc = 250 ° C. to 320 ° C. As the characteristics, d33 = 300 to 650 pC / N, which was almost the same value as in Example 1.
[0022]
In the present invention, a carbonate such as BaCO ₃ is used as a starting material, but other compounds such as BaTiO ₃ and CaTiO ₃ may be used. Further, it is within the scope of the present invention to include a small amount of transition metal such as Mn, Co, Fe, etc. as long as these characteristics are not deteriorated. The content of these transition metals is at most 1 mol%.
[0023]
【The invention's effect】
As described in detail above, according to the present invention, a lead-free piezoelectric single crystal material having excellent dielectric / piezoelectric properties, in which a large single crystal having few inclusions, bubbles and cracks can be easily obtained, is provided. It can be stably provided at a practical level at low cost. In particular, it is possible to provide a lead-free piezoelectric material having a practical permittivity (≧ 1000), a Curie temperature (Tc ≧ 200 ° C.), and a large size (≧ 25 mm). The piezoelectric single crystal of the present invention is particularly effective as a vibrator of an ultrasonic probe, but is expected to exhibit an effect in electroacoustic transducers such as a piezoelectric buzzer. Note that the piezoelectric single crystal of the present invention does not use lead at all. For this reason, a large amount of lead oxide is volatilized into the atmosphere during heat treatment processes such as firing and melting, which cannot be avoided with lead-based piezoelectric materials such as PZT and PMN that are currently used in many piezoelectric application fields. , The diffusion can be completely eliminated. This is a fundamental solution to the lead problem that will inevitably arise in the future, and has a great effect in terms of ecological aspects and pollution control.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a growth apparatus for producing an oxide piezoelectric single crystal according to the present invention.
FIG. 2 is a schematic view of a piezoelectric single crystal wafer obtained according to the present invention.
FIG. 3 is a graph showing the relationship between inclusions, bubbles or cracks and the amount of Nb ₂ O ₅ added when growing a piezoelectric single crystal obtained in the present invention.
[Explanation of symbols]
1. . . Electric furnace 2. . . Heater 3. . . 3. platinum crucible . . Single crystal raw material5. . . Single crystal6. . . Wafer cut into {100} or {111} from single crystal

Claims (6)

A single-crystal composition that is a composite perovskite oxide , wherein an element D (D = Nb, Ta) compound ( where D is pentavalent , based on 100 mol% of a compound represented by the following general formula (1)) elements) oxide single crystal composition having the composition in a proportion of less than 5 mol% exceed 0 mol% at D in terms of element _{{(Bi 1/2, Na 1/2)} 1-x A1 x} TiO 3 ( 1)
(In the above general formula (1), x is a value of 0 ≦ x <1, and A1 is at least one selected from Ba, Ca, and Sr). A single crystal composition which is a composite perovskite oxide, wherein 100 mol% of a compound represented by the following general formula (2) is compounded with an element D (D = Nb, Ta) compound ( where D is a pentavalent compound ). elements) oxide single crystal composition having the composition in a proportion of less than 5 mol% exceed 0 mol% at D in terms of element _{{(Bi 1/2, Na 1/2)} 1-x (Bi 1/2, _{A2 1/2) x} TiO 3 (} 2)
(X in the general formula (2) is a value of 0 ≦ x <1, and A2 is at least one selected from Li, K, and Rb). 3. The oxide single crystal composition according to claim 1, wherein a part of Bi ^{3+ in} the formulas (1) and (2) represented by the formulas (1) and (2) is substituted with La ³⁺ . The crystal orientation of the piezoelectric single crystal composition composed of the composite perovskite oxide according to claim 1 or 2 is polarized in the {001} direction in the case of a rhombohedral structure, and in the case of a tetragonal phase. An oxide single crystal composition which is polarized in a {111} direction. A single crystal composition which is a composite perovskite oxide, wherein a compound represented by the following general formula (1) is compounded with 100 mol% of an element D (D = Nb, Ta) compound ( However, with this compound D Is a pentavalent element ) Is 0 mo in D element conversion l %, Cut out from an oxide single crystal composition having a composition containing more than 5% by mole and less than 5% by mole.
  ｛(Bi _1/2 , Na _1/2 ) _1-x A1 _x ｝ TiO ₃   (1)
(In the general formula (1), x is a value of 0 ≦ x <1, and Al is at least one selected from Ba, Ca, and Sr). A single crystal composition which is a composite perovskite oxide, wherein a compound represented by the following general formula (2) is compounded with 100 mol% of an element D (D = Nb, Ta) compound ( However, with this compound D Is a pentavalent element ) Is 0 mo in D element conversion l %, Cut out from an oxide single crystal composition having a composition containing more than 5% by mole and less than 5% by mole.
    ｛(Bi _1/2 , Na _1/2 ) _1-x (Bi _1/2 , A2 _1/2 ) _x ｝ TiO ₃ (2)
(The above general formula ( 2 ) X in the above is a value of 0 ≦ x <1, and A2 is at least one selected from Li, K, and Rb).

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