Suppose, we have a spinel AB2O4, Let A be Ge ;B= V, Cr, Mo.

X-ray diffraction studies indicate that the Ge occupy the A (tetrahedral) sites and Mo, V, and Cr the B (octahedral) sites. All of the spinels are semiconductors(SC) Their SC nature is explained by taking a simple case with A=Ge, B=Cr

Ge belongs to 14th group of the periodic table with outermost electronic configuration 4s^2 4p^2,i.e. have four electrons . It can become n- type as well as p- type SC as follows:

Ge can form four bonds with four more Ge atoms.

p- type Ge spinel becomes SC when a group 13 element (B,.Al,.-the dopants) having only 3 valence electrons is present as impurity as follows:

This electron deficient dopant forms three bonds with each one of the three Ge and leaves ONE BOND UNSATISFIED or a hole is created which otherwise would have contained one electron.In a way, this hole being empty is analogous to positive hole . With the presence of a definite mole % of the dopant, a large number of such holes are created in the Ge spinels. When potential differenc is applied, such holes can move across the crystal and can conduct electricity to some extent. As the electricity is conducted by the movement of these POSITIVE HOLES, hence such SC are called p-type SC.

n- type Ge spinel becomes (SC) when a group 15th group element dopant(P,As,Sb) having 5 valence electrons are present as impurity as follows:

These electron rich dopants form four bonds with each one of the four Ge and leave one electron FREE. With the presence of a definite mole % of the dopant, a large number of such free electrons now become available in the Ge spinels . When potential differenc is applied, such free electrons can move across the crystal and can conduct electricity in the NORMAL way, i.e., as it happens in metals where free electrons are the conductors. As the electricity is conducted by the movement of the electrons (in the normal way), hence such SC are called n-type SC.

As in n-type SC, the electricity is conducted the smallest free non restrictive electrons while in p-type SC, it is conducted the movements of finite sized positive holes whose free movement can be restricted by the neighbouring Ge /dopant species, p- tpye SC are expected to be less conducting .

Suppose, we have a spinel AB2O4, Let A be Ge ;B= V, Cr, Mo.

X-ray diffraction studies indicate that the Ge occupy the A (tetrahedral) sites and Mo, V, and Cr the B (octahedral) sites. All of the spinels are semiconductors(SC) Their SC nature is explained by taking a simple case with A=Ge, B=Cr

Ge belongs to 14th group of the periodic table with outermost electronic configuration 4s^2 4p^2,i.e. have four electrons . It can become n- type as well as p- type SC as follows:

Ge can form four bonds with four more Ge atoms.

p- type Ge spinel becomes SC when a group 13 element (B,.Al,.-the dopants) having only 3 valence electrons is present as impurity as follows:

This electron deficient dopant forms three bonds with each one of the three Ge and leaves ONE BOND UNSATISFIED or a hole is created which otherwise would have contained one electron.In a way, this hole being empty is analogous to positive hole . With the presence of a definite mole % of the dopant, a large number of such holes are created in the Ge spinels. When potential differenc is applied, such holes can move across the crystal and can conduct electricity to some extent. As the electricity is conducted by the movement of these POSITIVE HOLES, hence such SC are called p-type SC.

n- type Ge spinel becomes (SC) when a group 15th group element dopant(P,As,Sb) having 5 valence electrons are present as impurity as follows:

These electron rich dopants form four bonds with each one of the four Ge and leave one electron FREE. With the presence of a definite mole % of the dopant, a large number of such free electrons now become available in the Ge spinels . When potential differenc is applied, such free electrons can move across the crystal and can conduct electricity in the NORMAL way, i.e., as it happens in metals where free electrons are the conductors. As the electricity is conducted by the movement of the electrons (in the normal way), hence such SC are called n-type SC.

As in n-type SC, the electricity is conducted the smallest free non restrictive electrons while in p-type SC, it is conducted the movements of finite sized positive holes whose free movement can be restricted by the neighbouring Ge /dopant species, p- tpye SC are expected to be less conducting .

Dear Sir, I am very thankful to you for your clear explanation.

I want to add to above good explanation: ferrites or ferroxdure are semiconductors with high resistivity than normal semiconductor like Si or Ge doped semiconductors. In other words they have large forbidden energy gap than conventional one.