Abstract: A lithium tantalate substrate obtained by working in the state of a substrate a lithium tantalate crystal grown by the Czochralski method is buried in a mixed powder of Al and Al2O3, followed by heat treatment carried out at a temperature kept to from 350 to 600° C., to manufacture a lithium tantalate substrate having volume resistivity which has been controlled within the range of from 1010 to 1013 ?cm. The substrate obtained has a very low pyroelectricity or no pyroelectricity, and it can be made colored and opaque from a colorless and transparent state and also sufficiently has the properties required as a piezoelectric material.

Abstract: A lithium tantalate substrate obtained by working in the state of a substrate a lithium tantalate crystal grown by the Czochralski method is buried in a mixed powder of Al and Al2O3, followed by heat treatment carried out at a temperature kept to from 350 to 600° C., to manufacture a lithium tantalate substrate having volume resistivity which has been controlled within the range of from more than 108 to less than 1010 ?cm. The substrate obtained has no pyroelectricity, and it can be made colored and opaque from a colorless and transparent state and also sufficiently has the properties required as a piezoelectric material.

Abstract: A lithium tantalate substrate obtained by working in the state of a substrate a lithium tantalate crystal grown by the Czochralski method is buried in a mixed powder of Al and Al2O3, followed by heat treatment carried out at a temperature kept to from 350 to 600° C., to manufacture a lithium tantalate substrate having volume resistivity which has been controlled within the range of from more than 108 to less than 1010 ?cm. The substrate obtained has no pyroelectricity, and it can be made colored and opaque from a colorless and transparent state and also sufficiently has the properties required as a piezoelectric material.

Abstract: In a process for manufacturing a LT substrate from a LT crystal, after growing the crystal, a LT substrate in ingot form is imbedded in carbon power, or is place in a carbon vessel, and heat treated is conducted at a maintained temperature of between 650° C. and 1650° C. for at least 4 hours, whereby in a lithium tantalate (LT) substrate, sparks are prevented from being generated by the charge up of an electric charge on the substrate surface, and thereby destruction of a comb pattern formed on the substrate surface and breaks or the like in the LT substrate are prevented.

Abstract: In a process for manufacturing a LT substrate from a LT crystal, after growing the crystal, a LT substrate in ingot form is imbedded in carbon power, or is place in a carbon vessel, and heat treated is conducted at a maintained temperature of between 650° C. and 1650° C. for at least 4 hours, whereby in a lithium tantalate (LT) substrate, sparks are prevented from being generated by the charge up of an electric charge on the substrate surface, and thereby destruction of a comb pattern formed on the substrate surface and breaks or the like in the LT substrate are prevented.

Abstract: In a process for manufacturing a LT substrate from a LT crystal, after growing the crystal, a LT substrate in ingot form is imbedded in carbon power, or is place in a carbon vessel, and heat treated is conducted at a maintained temperature of between 650° C. and 1650° C. for at least 4 hours, whereby in a lithium tantalate (LT) substrate, sparks are prevented from being generated by the charge up of an electric charge on the substrate surface, and thereby destruction of a comb pattern formed on the substrate surface and breaks or the like in the LT substrate are prevented.

Abstract: A lithium tantalate substrate obtained by working in the state of a substrate a lithium tantalate crystal grown by the Czochralski method is buried in a mixed powder of Al and Al2O3, followed by heat treatment carried out at a temperature kept to from 350 to 600° C., to manufacture a lithium tantalate substrate having volume resistivity which has been controlled within the range of from more than 108 to less than 1010 ?cm. The substrate obtained has no pyroelectricity, and it can be made colored and opaque from a colorless and transparent state and also sufficiently has the properties required as a piezoelectric material.

Abstract: A lithium tantalate substrate obtained by working in the state of a substrate a lithium tantalate crystal grown by the Czochralski method is buried in a mixed powder of Al and Al2O3, followed by heat treatment carried out at a temperature kept to from 350 to 600° C, to manufacture a lithium tantalate substrate having volume resistivity which has been controlled within the range of from 106 to 108 ?cm. The substrate obtained has no piezoelectricity, and it can be made colored and opaque from a colorless and transparent state and also sufficiently has the properties required as a piezoelectric material.

Abstract: In a process for manufacturing a LT substrate from a LT crystal, after growing the crystal, a LT substrate in ingot form is imbedded in carbon power, or is place in a carbon vessel, and heat treated is conducted at a maintained temperature of between 650° C. and 1650° C. for at least 4 hours, whereby in a lithium tantalate (LT) substrate, sparks are prevented from being generated by the charge up of an electric charge on the substrate surface, and thereby destruction of a comb pattern formed on the substrate surface and breaks or the like in the LT substrate are prevented.

Abstract: In a method of producing a lithium niobate substrate by the use of a lithium niobate crystal grown by the Czochralski process, the lithium niobate crystal is heat-treated at a temperature of from 300° C. or more to less than 500° C. in the state the lithium niobate crystal is buried in a powder constituted of at least one element selected from the group consisting of Al, Ti, Si, Ca, Mg and C, or in the state the lithium niobate crystal is held in a container constituted of at least one element selected from the group consisting of Al, Ti, Si, Ca, Mg and C.

Abstract: In a process for manufacturing a LT substrate from a LT crystal, after growing the crystal, a LT substrate in ingot form is imbedded in carbon power, or is place in a carbon vessel, and heat treated is conducted at a maintained temperature of between 650° C. and 1650° C. for at least 4 hours, whereby in a lithium tantalate (LT) substrate, sparks are prevented from being generated by the charge up of an electric charge on the substrate surface, and thereby destruction of a comb pattern formed on the substrate surface and breaks or the like in the LT substrate are prevented.

Abstract: A lithium tantalate substrate obtained by working in the state of a substrate a lithium tantalate crystal grown by the Czochralski method is buried in a mixed powder of Al and Al2O3, followed by heat treatment carried out at a temperature kept to from 350 to 600° C., to manufacture a lithium tantalate substrate having volume resistivity which has been controlled within the range of from 1010 to 1013 ?cm. The substrate obtained has a very low pyroelectricity or no pyroelectricity, and it can be made colored and opaque from a colorless and transparent state and also sufficiently has the properties required as a piezoelectric material.

Abstract: A lithium tantalate substrate obtained by working in the state of a substrate a lithium tantalate crystal grown by the Czochralski method is buried in a mixed powder of Al and Al2O3, followed by heat treatment carried out at a temperature kept to from 350 to 600° C., to manufacture a lithium tantalate substrate having volume resistivity which has been controlled within the range of from 106 to 108 ?cm. The substrate obtained has no pyroelectricity, and it can be made colored and opaque from a colorless and transparent state and also sufficiently has the properties required as a piezoelectric material.

Abstract: In a process for manufacturing a LT substrate from a LT crystal, after growing the crystal, a LT substrate in ingot form is imbedded in carbon power, or is place in a carbon vessel, and heat treated is conducted at a maintained temperature of between 650° C. and 1650° C. for at least 4 hours, whereby in a lithium tantalate (LT) substrate, sparks are prevented from being generated by the charge up of an electric charge on the substrate surface, and thereby destruction of a comb pattern formed on the substrate surface and breaks or the like in the LT substrate are prevented.

Abstract: In a method of producing a lithium niobate substrate by the use of a lithium niobate crystal grown by the Czochralski process, the lithium niobate crystal is heat-treated at a temperature of from 300° C. or more to less than 500° C. in the state the lithium niobate crystal is buried in a powder constituted of at least one element selected from the group consisting of Al, Ti, Si, Ca, Mg and C, or in the state the lithium niobate crystal is held in a container constituted of at least one element selected from the group consisting of Al, Ti, Si, Ca, Mg and C.

Abstract: In a process for manufacturing a LT substrate from a LT crystal, after growing the crystal, a LT substrate in ingot form is imbedded in carbon power, or is place in a carbon vessel, and heat treated is conducted at a maintained temperature of between 650° C. and 1650° C. for at least 4 hours, whereby in a lithium tantalate (LT) substrate, sparks are prevented from being generated by the charge up of an electric charge on the substrate surface, and thereby destruction of a comb pattern formed on the substrate surface and breaks or the like in the LT substrate are prevented.

Abstract: A video tape recorder has a recording current setting unit for setting recording currents to be supplied to a recording head for recording audio and video signals on a magnetic tape. The recording current setting unit controls electronic volume controls to adjust and output audio and video signals to set the recording currents. Level detectors detect reproduced signals, which have been recorded on the magnetic tape by the recording head, and supply the detected signals to the recording current setting unit. The recording current setting unit controls the electronic volume controls to hold the audio signal at a constant level and to simultaneously vary levels of luminance and chrominance signals of the video signal with the levels being kept at a constant ratio, and at the same time controls the recording head to preliminarily magnetically record the audio and video signals on the magnetic tape.