Aoki H, Kato K, Ebihara M, Inoue M
Shika Rikogaku Zasshi. 1976 Sep;17(39):200-5.
Apatite ceramics is composed of hydroxyapatite [Ca10(PO4)6(OH)2] sintered at high temperature. It is known that hydroxyapatite is the main component of bone and tooth minerals. There are two synthetic methods for the apatite powder. One is so called wet synthetic method: Synthesis by the reaction of Ca++ and PO4--- in the aqueous solution of approximately pH 7.0, the other is dry method: Synthesis by the solid state reaction at high temperature. The apatite powder stable below 1400 degrees C was prepared by the latter method in this work. After passing through a sieve, this powder was cold-pressed and then sintered at 1000 degrees C to 1300 degrees C in air. Biological apatite powders were also perpared as a reference. It was found that any apatite ceramics having porosity in the range of 5 to 50% could be obtained under the various sintering conditions. Compressive strength of these apatite ceramics increased with the reduction of the porosity, and those with porosity less than 20% were more than 100 kg/cm2. Vickers hardness was measured. This result showed the same tendency as that of compressibility. Hardness of the apatite ceramics with 90% relative density was almost the same or more as that of enamel. Solubility of the synthetic apatite powder in distilled water and aqueous solution of lactic acid (pH 4.0) was nearly the same as biological apatites. The dissolution rate decreased with the reduction of porosity of the ceramics. It was certified that hot pressing technique was extremely effective to obtain high density ceramics (more than 95% of density) and thus low parosity apatite ceramics. From the facts as described above, it is understood that sintered pure hydroxy-apatite is an excellent ceramics of high mechanical strength.
磷灰石陶瓷由高温烧结的羟基磷灰石[Ca10(PO4)6(OH)2]组成。众所周知，羟基磷灰石是骨骼和牙齿矿物质的主要成分。磷灰石粉末有两种合成方法。一种是所谓的湿法合成：在pH约为7.0的水溶液中通过Ca++和PO4---反应合成，另一种是干法：通过高温固态反应合成。在本工作中，采用后一种方法制备了在1400℃以下稳定的磷灰石粉末。过筛后，将该粉末冷压，然后在空气中于1000℃至1300℃烧结。还制备了生物磷灰石粉末作为参考。发现在各种烧结条件下都可以获得孔隙率在5%至50%范围内的任何磷灰石陶瓷。这些磷灰石陶瓷的抗压强度随着孔隙率的降低而增加，孔隙率小于20%的陶瓷抗压强度超过100kg/cm2。测量了维氏硬度。结果显示出与压缩性相同的趋势。相对密度为90%的磷灰石陶瓷的硬度与牙釉质几乎相同或更高。合成磷灰石粉末在蒸馏水和乳酸水溶液（pH 4.0）中的溶解度与生物磷灰石几乎相同。溶解速率随着陶瓷孔隙率的降低而降低。经证实，热压技术对于获得高密度陶瓷（密度超过95%）以及因此低孔隙率的磷灰石陶瓷极其有效。从上述事实可以理解，烧结的纯羟基磷灰石是一种具有高机械强度的优异陶瓷。
