Three Solid Modifications of Ba[Ga(NH₂)₄]₂: A Soluble Intermediate in Ammonothermal GaN Crystal Growth

Abstract

Ammonothermally grown GaN crystals are highly demanded as superior substrates for manufacturing high-performance blue and white LEDs. Ba or Ba(NH 2 ) 2 can act as effective mineralizers under ammonothermal conditions (523 K, 110-150 MPa) and lead to the formation of barium bis(tetramidogallate), Ba[Ga(NH 2 ) 4 ] 2 , a new intermediate in h-GaN synthesis, which was obtained in three solid forms. Single crystals of all three modifications were characterized by X-ray diffraction [a]

Ammonothermal Synthesis of Nitrides: Recent Developments and Future Perspectives

“…To further optimize the crystal growth process, knowledge on intermediates and solubilities is fundamental. In recent years, several possible intermediate compounds for ammonobasic and ‐acidic systems were isolated . Such intermediates act as transporting agents for GaN from dissolution to the growth zone, where dissolution and complexing equilibria are controlled through the applied temperature gradient.…”

“…In recent years, several possible intermediate compounds for ammonobasic and -acidic systems were isolated. [60][61][62][63] Such intermediates act as transporting agentsf or GaNf rom dissolution to the growth zone, where dissolution and complexing equilibria are controlled through the applied temperature gradient. Numerical simulations additionally help to visualize fluid, mass, and heat flow of the convection-driven chemical transport reaction.…”

Crystalline Nitridophosphates by Ammonothermal Synthesis

“…While NaN 3 was added for the synthesis of Ca 2 PN 3 , to increase both, the solubility of Ca and P red , no additional mineralizer was added for the synthesis of SrP 8 N 14 . Instead, Sr(N 3 ) 2 acts as an ammonobasic mineralizer itself by forming Sr(NH 2 ) 2 , as the heavier alkaline earth metals have been discussed as ammonobasic mineralizers as well . Possible intermediates are mixed‐metal amides, such as NaCa(NH 2 ) 3 , and reactive P/N compounds, for example, hexaaminocyclotriphosphazene (PN(NH 2 ) 2 ) 3 , the corresponding ammoniate (PN(NH 2 ) 2 ) 3 ⋅ 0.5 NH 3 or imidonitrides in analogy to Na 10 [P 4 (NH) 6 N 4 ](NH 2 ) 6 (NH 3 ) 0.5 , which have already been synthesized using the ammonothermal method .…”

“…[5] The addition of these mineralizers can also dissolvecompounds such as P red ,w hich are actually insoluble in NH 3 even at temperaturesa bove the critical point. [35] Possible intermediates are mixed-metal amides, such as NaCa(NH 2 ) 3 ,a nd reactive P/N compounds, for example, hexaaminocyclotriphosphazene (PN(NH 2 ) 2 ) 3 ,t he corresponding ammoniate (PN(NH 2 ) 2 ) 3 ·0.5 NH 3 or imidonitrides in analogy to Na 10 [P 4 (NH) 6 N 4 ](NH 2 ) 6 (NH 3 ) 0.5 ,w hichh ave already been synthesized using the ammonothermal method. [35] Possible intermediates are mixed-metal amides, such as NaCa(NH 2 ) 3 ,a nd reactive P/N compounds, for example, hexaaminocyclotriphosphazene (PN(NH 2 ) 2 ) 3 ,t he corresponding ammoniate (PN(NH 2 ) 2 ) 3 ·0.5 NH 3 or imidonitrides in analogy to Na 10 [P 4 (NH) 6 N 4 ](NH 2 ) 6 (NH 3 ) 0.5 ,w hichh ave already been synthesized using the ammonothermal method.…”

“…[34] Therefore, in the case of the synthesized lithium nitridophosphates (a-Li 10 P 4 N 10 , b-Li 10 P 4 N 10 ,L i 18 P 6 N 16 and LiPN 2 ), Li 3 No rL iw as added,r espectively,i ne xcesst oi ncrease the solubility of P red .W hile NaN 3 was added for the synthesis of Ca 2 PN 3 ,t oi ncrease both, the solubility of Ca and P red ,n oa dditional mineralizer was added for the synthesis of SrP 8 N 14 .Instead,Sr(N 3 ) 2 acts as an ammonobasic mineralizer itself by forming Sr(NH 2 ) 2 ,a st he heavier alkaline earth metals have been discussed as ammonobasic mineralizers as well. [35] Possible intermediates are mixed-metal amides, such as NaCa(NH 2 ) 3 ,a nd reactive P/N compounds, for example, hexaaminocyclotriphosphazene (PN(NH 2 ) 2 ) 3 ,t he corresponding ammoniate (PN(NH 2 ) 2 ) 3 ·0.5 NH 3 or imidonitrides in analogy to Na 10 [P 4 (NH) 6 N 4 ](NH 2 ) 6 (NH 3 ) 0.5 ,w hichh ave already been synthesized using the ammonothermal method. [20,[36][37][38] A possible condensation mechanism of phosphorus containing intermediates is illustrated in Scheme 1.…”