Voltage nonlinear resistor and multilayer varistor using same
View Patent ↗A voltage nonlinear resistor includes a plurality of N-type ZnO crystal grains, a grain boundary layer, and an oxide grain as a P-type semiconductor. The grain boundary layer is formed between the ZnO crystal grains, and contains at least one kind of oxide of alkaline-earth metal. The oxide grain is disposed between the ZnO crystal grains via the grain boundary layer.
1. A voltage nonlinear resistor comprising:
a plurality of N-type ZnO crystal grains;
a grain boundary layer formed among the plurality of N-type ZnO crystal grains, and including an oxide containing an alkaline-earth metal; and
an oxide grain as a P-type semiconductor disposed among the plurality of N-type ZnO crystal grains via the grain boundary layer.
2. The voltage nonlinear resistor according to claim 1 , wherein
the alkaline-earth metal contained in the oxide constituting the grain boundary layer is selected from a group consisting of Sr, Ca, and Ba.
3. The voltage nonlinear resistor according to claim 1 , wherein
the oxide grain is made of a material identical to that of the grain boundary layer.
4. The voltage nonlinear resistor according to claim 1 , wherein
the grain boundary layer is a solid solution having a perovskite structure, and
the oxide grain is a solid solution having a perovskite structure.
5. The voltage nonlinear resistor according to claim 1 , wherein
a thickness of the grain boundary layer is 1 nm or more and 10 nm or less.
6. The voltage nonlinear resistor according to claim 1 , wherein
an average crystal grain size of the plurality of ZnO crystal grains is 0.5 μm or more and 2 μm or less.
7. The voltage nonlinear resistor according to claim 1 , containing
0.0001 mol or more and 0.003 mol or less of Al in Al 2 O 3 terms for 1 mol of ZnO that is contained in the nonlinear resistor.
8. A multilayer varistor comprising:
a pair of internal electrodes;
a varistor layer formed between the pair of internal electrodes; and
a pair of external electrodes electrically connected to the pair of internal electrodes, respectively,
wherein the varistor layer is formed of a voltage nonlinear resistor including:
a plurality of N-type ZnO crystal grains;
a grain boundary layer formed among the plurality of N-type ZnO crystal grains, and including an oxide containing an alkaline-earth metal; and
an oxide grain as a P-type semiconductor disposed among the plurality of N-type ZnO crystal grains via the grain boundary layer.
9. The multilayer varistor according to claim 8 , wherein
the alkaline-earth metal contained in the oxide constituting the grain boundary layer is selected from a group consisting of Sr, Ca, and Ba.
10. The multilayer varistor according to claim 8 , wherein
the oxide grain is made of a material identical to that of the grain boundary layer.
11. The multilayer varistor according to claim 8 , wherein
the grain boundary layer is a solid solution having a perovskite structure, and
the oxide grain is a solid solution having a perovskite structure.
12. The multilayer varistor according to claim 8 , wherein
a thickness of the grain boundary layer is 1 nm or more and 10 nm or less.
13. The multilayer varistor according to claim 8 , wherein
an average crystal grain size of the plurality of ZnO crystal grains is 0.5 μm or more and 2 μm or less.
14. The multilayer varistor according to claim 8 , containing
0.0001 mol or more and 0.003 mol or less of Al in Al 2 O 3 terms for 1 mol of ZnO that is contained in the nonlinear resistor.