An aluminum nitride particle including at least a first truncated six-sided pyramid (1-a) and a second truncated six-sided pyramid (1-b), the aluminum nitride particle having a shape such that a lower base (3) of the first truncated six-sided pyramid (1-a) and a lower base (3) of the second truncated six-sided pyramid (1-b) face each other, the first truncated six-sided pyramid (1-a) and the second truncated six-sided pyramid (1-b) each having an upper base (2) with an area S1 of not less than 60 μm.sup.2 and not more than 4800 μm.sup.2, and each having a ratio (S1/S2) of the area S1 to an area S2 of the lower base (3) being not less than 0.5 and less than 1, the first truncated six-sided pyramid (1-a) and the second truncated six-sided pyramid (1-b) respectively having a height h1 and a height h2 each being not less than 5 μm and not more than 20 μm.

Provided is a piezoelectric thin film device containing: a first electrode layer; and a piezoelectric thin film. The first electrode layer contains a metal Me having a crystal structure. The piezoelectric thin film contains aluminum nitride having a wurtzite structure. The aluminum nitride contains a divalent metal element Md and a tetravalent metal element Mt. [Al] is an amount of Al contained in the aluminum nitride, [Md] is an amount of Md contained in the aluminum nitride, [Mt] is an amount of Mt contained in the aluminum nitride, ([Md]+[Mt])/([Al]+[Md]+[Mt]) is 36 to 70 atom %. L.sub.ALN is a lattice length of the aluminum nitride in a direction that is approximately parallel to a surface of the first electrode layer with which the piezoelectric thin film is in contact, L.sub.METAL is a lattice length of Me in a direction, and L.sub.ALN is longer than L.sub.METAL.

Provided is a piezoelectric thin film device containing: a first electrode layer; and a piezoelectric thin film. The first electrode layer contains a metal Me having a crystal structure. The piezoelectric thin film contains aluminum nitride having a wurtzite structure. The aluminum nitride contains a divalent metal element Md and a tetravalent metal element Mt. [Al] is an amount of Al contained in the aluminum nitride, [Md] is an amount of Md contained in the aluminum nitride, [Mt] is an amount of Mt contained in the aluminum nitride, ([Md]+[Mt])/([Al]+[Md]+[Mt]) is 36 to 70 atom %. L.sub.ALN is a lattice length of the aluminum nitride in a direction that is approximately parallel to a surface of the first electrode layer with which the piezoelectric thin film is in contact, L.sub.METAL is a lattice length of Me in a direction, and L.sub.ALN is longer than L.sub.METAL.

To produce aluminum nitride in the form of a lump that can easily be broken down by light pulverization, which could not be obtained by a conventional combustion synthesis method. A method for producing aluminum nitride powder by a combustion synthesis method using a metallic aluminum powder, characterized in that a powder mixture in which an aluminum nitride powder having an average primary particle diameter of 3 μm or less as a diluent is mixed with a metallic aluminum powder in a ratio of 150 to 400 parts by mass of the aluminum nitride powder relative to 100 parts by mass of the metallic aluminum powder, is ignited to combust in a nitrogen atmosphere.

The invention provides highly transparent single crystalline AlN layers as device substrates for light emitting diodes in order to improve the output and operational degradation of light emitting devices. The highly transparent single crystalline AlN layers have a refractive index in the a-axis direction in the range of 2.250 to 2.400 and an absorption coefficient less than or equal to 15 cm-1 at a wavelength of 265 nm. The invention also provides a method for growing highly transparent single crystalline AlN layers, the method including the steps of maintaining the amount of Al contained in wall deposits formed in a flow channel of a reactor at a level lower than or equal to 30% of the total amount of aluminum fed into the reactor, and maintaining the wall temperature in the flow channel at less than or equal to 1200° C.

The invention provides highly transparent single crystalline AlN layers as device substrates for light emitting diodes in order to improve the output and operational degradation of light emitting devices. The highly transparent single crystalline AlN layers have a refractive index in the a-axis direction in the range of 2.250 to 2.400 and an absorption coefficient less than or equal to 15 cm-1 at a wavelength of 265 nm. The invention also provides a method for growing highly transparent single crystalline AlN layers, the method including the steps of maintaining the amount of Al contained in wall deposits formed in a flow channel of a reactor at a level lower than or equal to 30% of the total amount of aluminum fed into the reactor, and maintaining the wall temperature in the flow channel at less than or equal to 1200° C.

In various embodiments, single-crystal aluminum nitride boules and substrates have low Urbach energies and/or absorption coefficients at deep-ultraviolet wavelengths. The single-crystal aluminum nitride may function as a platform for the fabrication of light-emitting devices such as light-emitting diodes and lasers.

In various embodiments, controlled heating and/or cooling conditions are utilized during the fabrication of aluminum nitride single crystals and aluminum nitride bulk polycrystalline ceramics. Thermal treatments may also be utilized to control properties of aluminum nitride crystals after fabrication.

In various embodiments, controlled heating and/or cooling conditions are utilized during the fabrication of aluminum nitride single crystals and aluminum nitride bulk polycrystalline ceramics. Thermal treatments may also be utilized to control properties of aluminum nitride crystals after fabrication.

The purpose of the present is to provide a modified AlN source for suppressing downfall defects. This manufacturing method of a modified aluminum nitride source involves a heat treatment step for heat treating an aluminum nitride source and generating an aluminum nitride sintered body.